Country：Japan

Award type：Honored in official journal of a scientific society, scientific journal  Country：Japan

Award type：International academic award (Japan or overseas)  Country：Australia

Award type：Award from international society, conference, symposium, etc.  Country：Japan

Award type：Award from international society, conference, symposium, etc.  Country：Japan

Award type：Award from Japanese society, conference, symposium, etc.  Country：Japan

Award type：Award from Japanese society, conference, symposium, etc.  Country：Japan

Award type：Honored in official journal of a scientific society, scientific journal  Country：Japan

Country：Japan

Country：Japan

牧田真治

Award type：Honored in official journal of a scientific society, scientific journal  Country：Japan

井村　彰宏

Country：Japan

Country：Japan

Country：Japan

Country：Japan

モデル予測制御に基づくPMSMのトルク制御におけるデッドタイム補償　前田拓真

Country：Japan

Country：Japan

Country：Japan

Country：Japan

Country：Japan

Country：Japan

Country：Japan

Country：Japan

Country：Japan

Country：Japan

Country：Japan

Country：Japan

Country：Japan

Country：Japan

Country：Japan

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：2024 IEEE/SICE International Symposium on System Integration, SII 2024  

In recent years, robots that move on tubular structures have attracted much attention. These robots are used in a variety of applications and provide very significant benefits such as increased work efficiency, improved safety, and reduced work costs. Robots that move on tubular structures include robots that move while grasping objects, robots that move while attached by suction cups or adhesive materials, and robots that move by wheels. However, conventional robots have large, rigid parts and cannot move in confined environments because they need sufficient mechanical strength to climb against gravity. This is where our research group's Funabot-Finger Cot comes in. This device is a small device with pneumatically expandable artificial muscles fixed to a cloth, and its movement can be controlled by controlling the pattern of air pressure application. The repeated contraction and relaxation characteristics of the device suggest that it could be used as a robot that moves on a tubular structure that mimics the peristaltic movement of living organisms. Peristaltic motion is the coordinated contraction and relaxation of muscles, which allows the robot to move over the ground, gaps, and objects. The Funabot-Finger Cot makes several contributions. First, because it is made of flexible fabric, it can be wrapped around structures of various shapes. Its thinness also allows it to move efficiently in constrained environments that are difficult for conventional robots. Secondly Cost-effective and cost-saving. Because this is small robot and made of common fabric and a small amount of artificial muscle, they can be made inexpensively and easily. The most notable feature is its versatility. Finally, the fact that the actuator supports both circular longitudinal contraction allows for more complex movements. This study will focus on the third advantage in particular, evaluating movement over tubular structures in circular contraction and in longitudinal contraction.

DOI： 10.1109/SII58957.2024.10417394

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE Access  

We implemented and evaluated our previous path planning method for inspection using unmanned aerial vehicles (UAVs) in real-world, and identified its shortcomings in handling positioning errors. Then, we proposed an enhanced method to address this problem. The previous method theoretically guaranteed complete coverage of targets and data quality. However, we verified it in bridge inspection experiments and found that the former has not been ensured. The crucial factors of data omission are clarified as the errors in UAV positioning. Our previous method relies on appropriately setting ideal allowances to counteract positioning errors, which is challenging in practice. Therefore, we proposed an enhanced path planning method, which adaptively adjusts allowances according to positioning error to prevent omission while minimizing waypoints. In the simulation including positioning disturbances, the enhanced method consistently achieved full coverage in 1000 times simulation with over 28% waypoints less than the previous one.

DOI： 10.1109/ACCESS.2024.3359056

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Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ECCE Europe 2024 - Energy Conversion Congress and Expo Europe, Proceedings  

In this study, it is shown that the multiphase IM can be regarded as a superposition of independent, decoupled large-pole and small-pole IM by using the VSD conversion in a multiphase IM drive system (IMTS) that actively utilizes pole change. By deriving a mathematical formula, the factor of torque fluctuation response due to conflict of voltage limiter during pole number change is identified. In addition, the pole change law without torque fluctuation in multiphase IM is proposed by using the formula.

DOI： 10.1109/ECCEEurope62508.2024.10751919

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ECCE Europe 2024 - Energy Conversion Congress and Expo Europe, Proceedings  

As the theories for expanding the operation range, the inverter overmodulation strategy and the flux weakening control method are widely used on the three-phase motors. In conventional research, it was found that a dual three-phase motor can be field-oriented-controlled in the overmodulation region easier than a three-phase motor. In this study, the theory of utilizing the flux weakening control and inverter overmodulation together for Dual Three-Phase Synchronous Motor is proposed, and the current reference calculation method under the flux weakening control is presented. The expansion performance of the proposed field-oriented control operation range is evaluated.

DOI： 10.1109/ECCEEurope62508.2024.10751838

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE Access  

This paper investigates the feasibility and effectiveness of applying AR (Augmented Reality) technology to assist UAV (Unmanned Aerial Vehicle) pilots in collecting data for structure inspections. The challenge of using UAVs to collect inspection data is that pilots could not precisely determine where to collect qualified data. Using AR technology to provide visual assistance to pilots is expected to tackle this challenge. However, previous research has focused on enhancing pilots' perception of UAVs' current situations and goal waypoints. How to indicate ideal data collection poses (positions and orientations) with AR and the practical improvement that AR can bring remain unknown. Therefore, we proposed a system that visualizes ideal poses as AR models, allowing pilots to easily collect qualified data by aligning UAVs with these models and taking images. Experiments in virtual and real confirmed that the system significantly improves the proportion of the valid inspection area (achieving up to 99.3%).

DOI： 10.1109/ACCESS.2024.3461174

Open Access

Web of Science

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Proceedings of the 2024 IEEE International Conference on Cyborg and Bionic Systems, CBS 2024  

Various haptic devices are attracting attention in many fields. However, conventional haptic devices have some limits. Electrical stimulation devices are lightweight and flexible, but the area in which the tactile stimulation is provided is spatially limited, and the variation of the tactile stimulation is few. The mechanical stimulation method can provide a widely stable tactile sensation, but it requires a rigid drive or limited mounting area. We developed a fabric actuator that is flexible and freely deformable soft actuator. This actuator is expected to be used in haptic devices, and it was clarified that the device can evoke an unprecedented pinched sensation by the wearer's sensation. However, it was not clear what mechanism evoked the pinched tactile. In this paper, we used a distribution sensor that can measure shear force to clarify the mechanism. Based on the results of the experiments, it was clarified that the three-dimensional intersections of the artificial muscles evoke a variety of force directions, contributing to the induction of the pinched tactile stimuli that were not previously possible.

DOI： 10.1109/CBS61689.2024.10860666

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：2024 18th International Conference on Control, Automation, Robotics and Vision, ICARCV 2024  

Compliance is important for the rehabilitation of wearable assistive robots. Various methods have been studied to improve the compliance of wearable robots, such that the use of impedance control of actuators and soft actuators with high compliance. On the other hand, for robots whose degrees of freedom of movement are limited by rotational axes like conventional robots, compliance performance may deteriorate due to mounting misalignment even if the actuator is designed optimally. Soft wearable devices that do not have rigid joints and are composed of soft base materials also exist, but the force is dispersed and cannot exert great force. Our Funabot- Plate consists of a base cloth, McKibben-type pneumatic artificial muscles, and thin, rigid plates that efficiently transfer the exerted force of the artificial muscles to the human body. Thus, Funabot-Plate expects a high output efficiency while high compliance. To verify the structural validity of the Funabot- Plate, two experiments were conducted to quantitatively compare its compliance characteristics with the rigid-frame robot. Through the measurement experiments, we were able to quantitatively evaluate that the structure of Funabot- Plate exhibited higher compliance in both conditions, transparent mode and assist mode, when compared to conventional rigid-frame robots.

DOI： 10.1109/ICARCV63323.2024.10821572

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：10th 2024 International Conference on Control, Decision and Information Technologies, CoDIT 2024  

This manuscript investigates the impact of unmanned aerial vehicles (UAVs) and their cameras' key specifications on the efficiency of infrastructure visual inspections using UAVs. The challenges of UAV-based inspection data collection include reducing necessary waypoints to improve inspection efficiency while collecting desired data for sure. Existing studies generally concentrated on optimizing the efficiency of UAVs' inspection trajectories and waypoints when equipment is given. However, the impacts of equipment specifications and their selections have not been investigated, yet they also significantly affect inspection efficiency. This manuscript surveys the key specifications of current equipment available for inspection and investigates the variation in efficiency through inspection simulations with different equipment specification combinations. Simulation results reveal that with the highest pose accuracy achievable by existing UAV platforms, it is possible to achieve efficient inspection. However, such high pose accuracy may be difficult to achieve, underscoring the importance of targeted selection of camera focal lengths according to UAV specifications and the types of pose errors. Additionally, using higher-resolution cameras may substantially improve the efficiency of high-resolution data collection tasks, which is a more practical solution for enhancing efficiency than further improvements in UAV pose accuracy. The conclusions drawn from this research provide actionable guidelines for equipment selection and development and lay the foundations of efficiency modeling, ultimately contributing to the advancement of UAV-based inspection methodologies.

DOI： 10.1109/CoDIT62066.2024.10708530

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：2024 IEEE International Conference on Electrical Systems for Aircraft, Railway, Ship Propulsion and Road Vehicles and International Transportation Electrification Conference, ESARS-ITEC 2024  

In this study, it is shown that the multiphase IM can be regarded as a superposition of independence, decoupled large-pole and small-pole IM by using the VSD conversion and multiphase IM drive system (IMTS: Induction Motor drive with Transmission System) that actively utilizes pole change is proposed. By deriving a mathematical formula, the factor of torque fluctuation response due to conflict of voltage limiter during pole number change is identified. In addition, the pole change law without torque fluctuation in multiphase IM is proposed by using the formula. An actual machine experiment is also conducted to confirm the effectiveness of the proposed method.

DOI： 10.1109/ESARS-ITEC60450.2024.10819802

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Proceedings of the 2024 IEEE International Conference on Cyborg and Bionic Systems, CBS 2024  

Various haptic devices are attracting attention in many fields, and research and development on haptic devices using soft actuators are underway. We developed a fabric actuator that is flexible and freely deformable soft actuator. This actuator is expected to be used in haptic devices, and it was clarified the device can evoke Grasp, Pinch, Press, and Twist tactile at one actuator in the upper arm and forearm. We focus on the site extensibility of this actuator. In this paper, we verified what types of tactile sensations this actuator can evoke in the shin and calf via experiments with one experimenter as the subject. As a result, mainly three results were obtained: The first was the area where the tactile work was accurately answered. Second, the subject was confused about whether the pattern was Press or Grasp. Third, it was difficult to evoke Pinch tactile. After consideration, it was suggested that the method of attachment is important. In the future, we aim to achieve diverse tactile recall with the leg while investigating other causes.

DOI： 10.1109/CBS61689.2024.10860485

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：2024 IEEE International Conference on Electrical Systems for Aircraft, Railway, Ship Propulsion and Road Vehicles and International Transportation Electrification Conference, ESARS-ITEC 2024  

The field-oriented control (FOC)-based auto current regulators (ACRs) are commonly designed under the ideal assumption that the phase is obtained continuously when performing the Park transformation, but the current regulators are always discretely implemented. It will inevitably introduce non-negligible phase discretization errors with the increase of fundamental-to-switching(control) frequency ratio (fe/fs). Therefore, an innovative discrete-time dq-axis model for AC motor considering the Park transformation phase discretization error is proposed and the corresponding ACR is designed. Then, the decoupling performance and stability of the proposed closedloop current system are theoretically analyzed using complex vector method. Furthermore, the proposed discretization method is subsequently performed on an induction motor (IM) and verified through simulations and experiments. Eventually, the Padé approximant order of the discrete control matrix is discussed.

DOI： 10.1109/ESARS-ITEC60450.2024.10819793

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.birob.2023.100127

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IET Electric Power Applications  

Finite control set model predictive control (FCS–MPC) has been deployed extensively in electric motor drives and power electronics applications. Many advantages, including fast transient response, have been reported. However, the improvement of its steady-state performance, that is, suppression of current ripple, is one of the main problems of a conventional FCS–MPC strategy. This article presents a current control strategy based on FCS–MPC using the concept of variable voltage smoothing. In the proposed method, a finite set of novel voltage vectors, produced by the smoothing process, are introduced as candidate control input candidates, and the controller generates the optimum output voltage using a modulator integrated with the FCS–MPC scheme. Thus, the voltage candidates are generated flexibly, and a suitable voltage for acceptable steady-state performance is determined as the control input. In addition, the smoothness in the proposed concept can be updated automatically depending on the drive situation, that is, transient, or steady-state operation, thus avoiding degradation of dynamic performance. Simulation and experimental results obtained with a permanent magnet synchronous motor drive system demonstrate that the proposed control strategy is effective to achieve current control with fast tracking performance while suppressing current ripple.

DOI： 10.1049/elp2.12335

Web of Science

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE Transactions on Industrial Electronics  

A direct speed control strategy based on finite control set model predictive control (FCS-MPC) with a voltage smoother is presented herein. In the proposed concept, a finite set of smoothed voltage vectors characterized by an adjustable amplitude and a movable origin is introduced as voltage candidates in the FCS-MPC scheme. The controller predicts the future current and speed and outputs the optimal smoothed voltage using pulse-width modulation. Owing to this control scheme, an abrupt change in the output voltage, which causes a large current ripple, is avoided without additional computational costs. Simulation and experimental results obtained using a permanent magnet synchronous motor fed by a two-level three-phase inverter show that the proposed method effectively reduces the current ripple while achieving a high dynamic drive compared with the conventional FCS-MPC scheme.

DOI： 10.1109/TIE.2022.3174298

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Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE Transactions on Industry Applications  

As competitive alternatives to conventional three-phase synchronous machines, synchronous multi-three-phase machines (MTPMs) are gaining increasing interests in various fields such as electrified transportation and power generation. The modular configuration is preferred for multi-three-phase drives in specific applications regarding the availability of advanced three-phase power electronics techniques and the superior capability of fault tolerance. The multi-stator (MS) modelling would be an ideal solution for the control of such modular drives as it facilitates power sharing among winding sets in a straightforward way and enables simple post fault strategies compared with the well-known vector space decomposition (VSD) modelling approach. Nevertheless, the strong magnetic coupling existing in MS model has hindered its use due to the instability and the performance deterioration issue. To solve the problem, a new decoupling control scheme directly applied in MS frame is proposed in this paper. The proposed method can deal with non-salient multi-three-phase machines whose three-phase winding sets can be identical or different, under the assumption of the sinusoidal airgap flux. Furthermore, it is shown by analysis the proposed method is characterized by significant simplicity and flexibility compared with the existing decoupling methods. The effectiveness of the proposed method has been verified through experiments including a single-side operation, a power-sharing test, and a post fault tolerant operation on a non-salient dual three-phase permanent magnet synchronous machine with quasi sinusoidal air gap flux.

DOI： 10.1109/TIA.2022.3211827

Open Access

Web of Science

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEJ Journal of Industry Applications  

This paper presents a stabilization method for different dual parallel surface permanent magnet synchronous motor (SPMSM) systems with a single inverter. When a single inverter drives two synchronous motors, disturbance can cause a torque difference between the two motors. This can cause the motor’s electrical and mechanical resonance. Several damping control methods have been proposed to suppress such resonance. However, such methods consider that the parameters of the two motors are identical. When a single inverter controls two motors with different parameters, the damping control performance deteriorates. Besides, the motor’s resonance sound and current ripple increase. To address these problems, this paper proposes a control method for dual-parallel-SPMSM drive systems with a single inverter.

DOI： 10.1541/ieejjia.22006418

Open Access

Web of Science

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEJ Journal of Industry Applications  

This paper proposes a novel extended electromotive force (EEMF) observer of a dual three-phase permanent magnet synchronous motor (DTP-PMSM) operable to the position sensorless overmodulation drive. The overmodulation drive occurs in current harmonics, and the estimated EEMF also contains harmonic components, leading to ripple error in the estimated position. Based on the vector space decomposition (VSD) utilized in DTP-PMSM current control, the proposed method can decrease the current harmonics in the overmodulation and the harmonic components in the estimated EEMF, and it can also improve position estimation. The effectiveness of the proposed EEMF observer and the improvement in the position estimation were experimentally verified.

DOI： 10.1541/ieejjia.22005441

Web of Science

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：4th International Conference on Electrical, Communication and Computer Engineering, ICECCE 2023  

Currently, vehicles are equipped with various sensors that can collect a series of driving behavior data while driving. The driving behavior data obtained in this way can be used to analyze the causes of traffic accidents and evaluate driver skills. However, when performing the above analysis, a specific driving scene is defined and driving behavior data for that driving scene is required. On the other hand, the series of driving behavior data obtained during one driving operation is enormous, and it is not easy to pick up desired driving scene data from among them. This research aims to establish a driving scene clustering method for a series of driving behavior data. In this paper, a driving scene is defined as a scene in which road shape and operation are associated, and propose a driving scene clustering method considered road shape. Here, a road map image is acquired from position information obtained from a GPS sensor, and the relationship between the road map image and operation data is clustered based on Coupled-GP-HSMM.

DOI： 10.1109/ICECCE61019.2023.10442604

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：2023 25th European Conference on Power Electronics and Applications, EPE 2023 ECCE Europe  

This paper proposes a novel capacitor current reduction method in Dual Three-Phase PMSM Drive System. By using Model Predictive Control considering the dead time on the premise of implementation, the method modifies the three-phase voltage command generated by the PI current controller for the current reduction. The effectiveness is verified by simulation and experiment.

DOI： 10.23919/EPE23ECCEEurope58414.2023.10264351

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE Access  

We developed a wearable assistive robot that directly measures the contact force acting between the robot and the human body, aiming to enhance the safety of such wearable devices. The force acting on the body is not directly measured, instead, it is estimated by measuring the torque acting on the robot joint in the wearable assistive robot. Despite the risk of failing to recognize dangerous forces due to modeling errors, the forces actually at work have not been examined. Here, we developed an arm-mounted assistive robot that directly measures the contact force as the distribution information to build a system and evaluate safety; in addition, the contact state between the robot and the human body was discussed. Accordingly, two experiments were conducted with 10 subjects. The first verified the contact force measurement performance of the robot, while the second demonstrated the application of contact force information to check the safety of the robot. The proposed robot can accurately measure the contact force, and the robot movement is safe under general control, for example, using the pain tolerance limit as the safety index. This eliminated the risk of not directly monitoring the forces acting on the surface of the human body. Furthermore, our result have implication for evaluating structural problems of the robot by evaluating contact conditions during movements.

DOI： 10.1109/ACCESS.2023.3324417

Web of Science

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE Canadian Journal of Electrical and Computer Engineering  

Finite control set-model predictive control (FCS-MPC) has a simple and intuitive optimization procedure. Therefore, FCS-MPC is increasingly being applied to control strategies for electrical drive systems. This article presents a method for servo brake control of a permanent magnet synchronous motor (PMSM) based on FCS-MPC. Accordingly, we propose a reference trajectory introduced in a cost function for brake motions and an alternating procedure with speed control. Moreover, this article clarifies the problem peculiar to servo-brake control using FCS-MPC, i.e., the reduction in tracking performance near the brake position because of the low resolution of the output voltage. In addition to the conventional method, a finite number of smoothed voltages were applied as candidate voltages for FCS-MPC to improve the tracking performance near the brake position. The smoothed voltages can effectively increase the resolution of the output voltage, which results in fewer steady-state errors in angular position tracking during servo brake motion. The simulation and experimental results obtained using a PMSM drive system reveal that the proposed strategy exhibited high performance in tracking the reference target during the operation of servobrakes and the ability to seamlessly alternate between servo brake and motor operations.

DOI： 10.1109/ICJECE.2022.3233029

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Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：2023 25th European Conference on Power Electronics and Applications, EPE 2023 ECCE Europe  

In this paper, we propose the control model for a novel dual three-phase PMSM with pseudo-triple winding structure(DTP-PMSM with PTWS) which is one of the new multiple stator winding machines. The proposed control model is represented as the extended form of the conventional dual three-phase winding machine, and the validity is demonstrated by being compared with magnetic field analysis results. Furthermore, the current vector controller for the control model is designed and its performance is confirmed by simulation.

DOI： 10.23919/EPE23ECCEEurope58414.2023.10264324

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：2023 25th European Conference on Power Electronics and Applications, EPE 2023 ECCE Europe  

Position sensorless control for Permanent-magnet synchronous motors has been investigated in numerous studies, but the issues of flying start at high speed are still a major problem. In our previous research, the issues on conventional position control are presented, and the reasons for these issues are distinguished as the initial response of the speed estimation. Based on this discussion, an initial speed estimation method is proposed as a solution. In this paper, the whole position sensorless control system with the initial speed estimation is presented, which enables the startup from overall speed, and the evaluation experiments are reported.

DOI： 10.23919/EPE23ECCEEurope58414.2023.10264244

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEJ Journal of Industry Applications  

This paper presents optimal current-control methods for driving two different synchronous motors using a single inverter. When one inverter drives two motors, system efficiency will deteriorate if their loads are not identical. Moreover, even with identical loads, system efficiency will deteriorate if the parameters of the two motors are not identical. To address this issue, this paper proposes optimal current-control methods for systems with two different motors driven by a single inverter.

DOI： 10.1541/ieejjia.22010492

Web of Science

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ICPE 2023-ECCE Asia - 11th International Conference on Power Electronics - ECCE Asia: Green World with Power Electronics  

When one inverter drives both motors, the system efficiency deteriorates if both motors have different loads. Moreover, even if their loads are the same, the system efficiency would also deteriorate if the parameters of both motors are different. To address this issue, this paper proposes optimal current control methods for both different motors using a single inverter.

DOI： 10.23919/ICPE2023-ECCEAsia54778.2023.10213583

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：2023 International Future Energy Electronics Conference, IFEEC 2023  

Position sensorless control of surface permanent magnet synchronous motors (SPMSMs) in low-speed regions is challenging because the motor has no magnetic saliency. Several methods using the block commutation drive technique to overcome this problem have been proposed; however, the rotor position is estimated only every 60° owing to the features of the block commutation drive method. Therefore, in this study, we proposed a novel sensorless rotor position estimation method by pasting the conductive nonmagnetic materials on the rotor. When high-frequency voltage is applied, eddy currents flow through the materials and the inductance slightly changes depending on the rotor position. In this study, estimating the continual rotor position from 0° to 360°, in which the sinusoidal vector control commutation is necessary rather than the block commutation drive method, was realized using these inductance changes. Based on the experimental results, we found that the rotor position could be continually estimated from 0 to 360°, which is necessary for sinusoidal vector commutation for an SPMSM with a position estimation error of approximately 6°, although the rotor velocity was low at 1.59 % of the rated velocity and 12 % of the rated load was applied.

DOI： 10.1109/IFEEC58486.2023.10458604

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE Robotics and Automation Letters  

In this letter, we propose to turn various existing cloths, especially functional cloths, into actuators by combined embroidery technology and thin McKibben artificial muscles. Most of the textile sensors so far are made by weaving active yarns into each other or into other base cloths. These devices have a limited choice of cloths that can be actuated. We create a prototypical actuator that can be deformed in three dimensions using thin artificial muscles and embroidery techniques on a functional cloth used for hook-and-loop fasteners and textiles that can observe pressure. Our experimental results indicate that the force of the artificial muscles can be transmitted to the cloth using fixation by embroidery and that the actuator can be variously deformed in three dimensions. We show that functional cloths can be made into actuators while maintaining their own functions using the proposed method.

DOI： 10.1109/LRA.2022.3157401

Web of Science

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：2022 IEEE/SICE International Symposium on System Integration, SII 2022  

This paper evaluates the performance of contact force-based control with developed wearable assistive robots enabling the contact force measurement between the wearer and the robot. Almost all the conventional assistive robots are controlled with their joint torque measured via torque sensors. These robots have risks exerting excessive force on the wearer because torque sensors cannot detect contact force exerting the wearer. Our research group developed the contact force-based control and evaluated its performance only on the simulation. Also, we developed a prototype of a wearable robot enabling to measure and detect the contact force. In this paper, tracking performance to the wearer's movements, one of the basic performances of wearable robots, is confirmed via the experience. As a result, contact force-based control can operate in full accordance with the command of zero contact force.

DOI： 10.1109/SII52469.2022.9708851

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEJ Journal of Industry Applications  

Dual three-phase permanent magnet synchronous motors have the characteristics of multi-phase and permanent magnet synchronous motors, whose double- and decoupled-winding models based on the vector space decomposition have been reported. High-frequency signal injection methods enable position sensorless control, parameter identification, and the search for maximum torque per ampere operating points. However, the current control system with high-frequency signal injection for a dual three-phase permanent magnet synchronous motor has not yet been sufficiently discussed. This study compares the double- and decoupled-winding models for the current control system with the high-frequency signal injection and proposes a current control system with high-frequency signal injection. Furthermore, this study proposes a position sensorless control method at low speed based on the high-frequency voltage injection as an application of the proposed current control system with the high-frequency signal injection. Experiments verify the effectiveness of the proposed current control system with the high-frequency signal injection and the proposed position sensorless control method.

DOI： 10.1541/ieejjia.20012955

Web of Science

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SAMI 2022 - IEEE 20th Jubilee World Symposium on Applied Machine Intelligence and Informatics, Proceedings  

The authors have been tackling a new teleoperation system with a head-mounted display (HMD) and an omnidirectional camera to reduce the workload of an operator. Some experimental results verified that presentation of AR images based on sensor information could reduce the workload and prevent the deterioration of the task quality due to the transmission delay of images. However, the range of the field of view (FOV) of an HMD is narrower than that of a human. This difference might cause accidents by overlooking hazards that are outside the FOV of the HMD. To solve this problem, the authors propose a new method of AR image presentation based on gaze information not to overlook hazards. Some experimental results using a driving simulator verified the usefulness of the proposed method.

DOI： 10.1109/SAMI54271.2022.9780732

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE International Symposium on Industrial Electronics  

The authors have been aiming to realize a remote driving system with an HMD(Head Mounted Display) and a 360-degree camera to decrease the task load of the operator. Therefore, we have been tackling an operator assistance method of remote driving applying Augmented Reality(AR). In the previously proposed methods, AR video presented to the operator is generated based on sensing information of 3D LiDAR to deal with the communication delay. In this paper, a new generation method of AR image is proposed, in which Gaze information of the operator is used to create a 3D object to draw his attention to a hazard that might cause a traffic accident. The usefulness of the proposed method has been evaluated based on the results of the experiments using a driving simulator which has a scenario of a person jumping out from a park.

DOI： 10.1109/ISIE51582.2022.9831663

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEJ Journal of Industry Applications  

To realize automated drive of a vehicle, more reliability to the motor drive system is required. The three phase dual winding permanent magnet motor drive using two inverters with corresponding voltage supplies is one of the potential candidates for the reliable motor drive system. With the respective voltage supply and winding connected to the inverter, the two motor drive systems are electrically independent. Thus, even if when a failure occurs in one of the systems, the other system can continue the motor drive. However, there is an issue: a voltage drop in one of the voltage supplies reduces the sinusoidal wave region of the drive system as the rotor of the motor is common in the two windings and the back electromotive voltage in the two windings are the same. The motor drive method that enlarges the applied voltage without causing high harmonics under the voltage supply unbalance in the three phase dual winding permanent magnet motor is proposed in this paper.

DOI： 10.1541/ieejjia.21009935

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Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：2022 International Power Electronics Conference, IPEC-Himeji 2022-ECCE Asia  

According to the increase in the required performance of the product, a multi-core processor that can process tasks simultaneously is attracting attention. To efficiently utilize a multi-core processor, a Model-Based Parallelization Tool(MBP) technology has been proposed to automatically generate paral-lelization code in consideration of the causal relationship of the control system. However, parallel processing time and control performance verification in real systems have not been sufficiently investigated. In this paper, to verify the validity of the parallelization code automatically generated by the MBP on a real system, we compare and review the single-code of the function unit by hand and the parallel code automatically generated by the MBP. In addition, we verify the MBP Tool by analyzing parallelization results as well as points to consider when implementing a motor control system.

DOI： 10.23919/IPEC-Himeji2022-ECCE53331.2022.9807202

Scopus

Authorship：Corresponding author   Language：Japanese   Publishing type：Research paper (international conference proceedings)   Publisher：2022 International Power Electronics Conference, IPEC-Himeji 2022-ECCE Asia  

In this paper, we propose a novel discrete current control scheme for IM (Inductive Motor). Ordinary, a current vector controller is designed by using the dq-axis model, which is induced under the assumption that Park transformation is continuously performed, and the designed controller is discretely implimented. If the sampling period is not short enough compared to the voltage supply frequency during high speed drive, these assumptions do not hold, and the control performance of the current system is greatly degraded, which results in control failure. To solve this problem, we proposed a discrete dq-axis IM model which is effective for low control period and high speed drive, and designed a current vector controller based on this model to improve control performance at high speed drive and confirmed the effect in simulation.

DOI： 10.23919/IPEC-Himeji2022-ECCE53331.2022.9807157

Scopus

Authorship：Corresponding author   Language：Japanese   Publishing type：Research paper (international conference proceedings)   Publisher：2022 International Power Electronics Conference, IPEC-Himeji 2022-ECCE Asia  

Extended electro-motive force (EEMF) estimation method is a fast position estimation method used for overall speed. In our previous research, we have reported the startup and drive method with EEMF from standstill. However, starting a free-running PMSM, which is known as the flying start, is rarely taken into consideration in the most position sensorless research. Under such condition, the rotor speed is unobservable before the startup. In this paper, a startup and driving strategy at overall speed with EEMF by speed and signal injection is proposed, and the evaluation experiments are reported.

DOI： 10.23919/IPEC-Himeji2022-ECCE53331.2022.9806847

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：2022 International Power Electronics Conference, IPEC-Himeji 2022-ECCE Asia  

This paper proposes a method to drive a single-inverter dual interior permanent magnet synchronous motor (IPMSM) system by using signal injection. Considerable research has been performed to decrease the size and cost of dual motor drive systems by driving two synchronous motors with one inverter. In general, the control is implemented considering one of the two motors. Such systems may become unstable because of the mechanical/electrical resonance occurring in the uncontrolled motor. Therefore, methods to suppress this resonance have been established. Notably, resonance control is challenging to implement at low speeds because the phase of the rotor with sensorless control cannot be easily estimated. To address this problem, signal injection and signal processing methods for such systems was established in this study.

DOI： 10.23919/IPEC-Himeji2022-ECCE53331.2022.9806970

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEJ Journal of Industry Applications  

This paper presents a coupling estimation based decoupled current vector control scheme for current control of a Dual Three Phase (DTP) Surface Permanent Magnet Synchronous Motor (SPMSM) drive with two micro control units (MCUs), to solve its inherent magnetic coupling issue. Aiming for an enhanced fault tolerance, the SPMSM drive utilized is a redundant and modular system composed of two subsystems in terms of three-phase inverters, sensing, and controllers, with respect to each winding set in the DTP SPMSM. The current of each winding set along with the rotor position is separately detected and applied for control by individually assigned MCU. This comprehensive modularity prevents interference between subsystems in local fault conditions, thus improving the fault tolerance capability. However, the magnetic coupling existing between the winding sets would deteriorate the performance and even cause instability in the whole system without proper decoupling control. Previous studies adopted communication between MCUs for real time current sampling sharing demanded by decoupling control. Nevertheless, communication bandwidth becomes a limiting factor of system design. Some general communication approaches would not satisfy the current sharing requirement of decoupling control for implementation. To eliminate this undesirable limit, a novel decoupled current vector control that utilizes a current observer to estimate the relevant magnetic coupling between winding sets is proposed in this paper. As validated from the experiment results, the proposed decoupled control scheme is able to decouple the system for dynamic improvement so that modularity of the drive can be achieved without communication, leading to an eventual improvement in fault tolerance capability.

DOI： 10.1541/ieejjia.22000073

Web of Science

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：2022 IEEE Energy Conversion Congress and Exposition, ECCE 2022  

This paper presents a control method for different dual-parallel-SPMSMs systems with a single inverter. Disturbance causes a torque difference between the two motors when one inverter drives two SPMSMs. This may lead to the motor's mechanical and electrical resonance. Several damping control methods have been proposed to suppress this resonance. However, such methods consider that the parameters of the two motors are identical. When one inverter controls two motors with different parameters, the damping control performance deteriorates. Additionally, the motor's resonance sound and motor current ripple increase. To solve these problems, this paper proposes a control method for dual parallel Surface Permanent Magnet Synchronous Motor (SPMSM) drive systems with a single inverter.

DOI： 10.1109/ECCE50734.2022.9947789

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE Access  

Flexible actuators are popular in the consumer and medical fields because of their flexibility and compliance. However, they are typically difficult to model because of their viscoelasticity and nonlinearity. This letter proposes a method for correcting the deformation of the simulated flexible robots to make it similar to the deformation of real robots using point clouds by deep learning. Long short-term memory (LSTM) can simulate the next frame of actuator deformation from the previous frames of deformations. In this study, we presented the robots with four different muscle structures. We found that using an encoder-LSTM-decoder network can improve the similarity between the deformation of a learned muscle structure and the real deformation and is also effective in correcting the deformation of the unlearned structures. Our correction method reduced the average Chamfer distance of the simulated point clouds of the basic-type structure actuator from 15.89 to 7.81. This research can provide a new concept for future flexible robot modeling using point clouds.

DOI： 10.1109/ACCESS.2022.3204652

Web of Science

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROBOMECH Journal  

Probabilistic localization based on Bayesian theory has been researched as a sensor fusion method to improve the robustness of localization. Pieces of position information, generated by sensors’ observation models with consideration for noises, are fused according to Bayesian theory. However, having large noises not considered in their observation models, the sensors output erroneous position information; thus, the fusion result has a significant error, even when the other sensors output correct ones. In this research, we have proposed a sensor fusion system with a relative correlation checking test to realize robust localization. Pieces of erroneous position information, biased against others and having a negative correlation with others, are detected and excluded in our proposed system by checking their correlation between all of them. The purpose of this paper is to evaluate the robustness of our fusion system by conducting recursive localization experiments in various environments.

DOI： 10.1186/s40648-021-00190-9

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEACon 2021 - 2021 IEEE Industrial Electronics and Applications Conference  

Synchronous reluctance motors (SynRMs) have attracted attention for various applications because they have no magnets and rotor windings. Thus, various methods for rotor position sensorless control of SynRMs at low speeds have been proposed. Similarly, we previously introduced a method for rotor position sensorless control of SynRMs at very low speeds. The proposed control method superimposes a high-frequency current with a small constant amplitude using a high-frequency current control system. The q-axis inductance of the SynRM considerably changes according to the load. In this paper, we show that the rotor position estimation error converges even under a large error between the predefined and real settings of the q-axis inductance of the SynRM model for position estimation when using the proposed method. Experimental results confirm that the proposed method achieves robust rotor position sensorless control against q-axis inductance variations even at very low speeds.

DOI： 10.1109/IEACon51066.2021.9654631

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IECON Proceedings (Industrial Electronics Conference)  

This paper proposes a capacitor current reduction method using real-time model predictive control (MPC) for a double three-phase permanent magnet synchronous motor (DTPPMSM) drive system. Capacitor current reduction for volume minimization of DTP-PMSM drive system is important issue. Optimizing switching timings by MPC is promising approach. However, it is difficult to implement ideal MPC in a real system because it requires a huge amount of calculation to predict the capacitor current. In this paper, we propose a new method that is possible to search optimal switching timing for reducing the capacitor current by using the MPC, whose calculation amount can be implemented in real-time. This paper shows the possibility of realizing an capacitor current reduction method with high control performance by reducing the amount of computation for MPC.

DOI： 10.1109/IECON48115.2021.9589070

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：2021 IEEE 10th Global Conference on Consumer Electronics, GCCE 2021  

In order to realize a remote car driving in an emergency situation or complicated environment, we propose a new method for operator support in teleoperation in this paper. In the proposed teleoperation system, it is supposed that there are two communication lines between an operator and the target remote driving car. The one is called as the main line, in which large data like image or sound are transferred allowing a large delay. The other is called as the subline, in which small data like emergency signals are transferred with a small delay. In the proposed method, an AR image is presented to an operator, in which 3D objects superimposed on a real image are generated using sensor data transferred through the subline. Due to the 3D objects with a small delay on a real image with a large delay, the operator can safely control the target car even if the image has an enormous delay caused by the bad communication status.

DOI： 10.1109/GCCE53005.2021.9622070

Scopus

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical Engineers of Japan (IEE Japan)  

DOI： 10.1541/ieejeiss.141.193

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：SAMI 2021 - IEEE 19th World Symposium on Applied Machine Intelligence and Informatics, Proceedings  

In this paper, we propose a new teleoperation system of a mobile robot using Augmented Reality(AR) based on 3D LiDAR information for operator support. In the proposed system, an 360-degree camera is equipped with a robot which works in a remote place controlled by an operator, and the captured 360-degree image is displayed to the head mounted display put on the head of the operator. The operator can smoothly control the robot watching what he needs for his task by turning his head. In addition, the provided image around the robot has no blind spot because of the 360-degree image. However, the data size of the 360-degree image is enormous and it causes a large transfer delay or dropped frames which adversely influence the operator performance. In order to solve this problem, it is proposed that an AR image is actually provided to the operator, in which objects generated based on 3D LiDAR information are superimposed on the 360-degree image as AR objects. In this paper, the usefulness of the proposed method is shown through the experimental results on parking the robot remotely.

DOI： 10.1109/SAMI50585.2021.9378687

Scopus

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEJ Journal of Industry Applications  

More reliable motor drive systems are expected in the realization of automated driving. The redundant motor drive system with two voltage supplies, two inverters, and a dual winding motor is one of the strong candidates since the two systems that construct the motor drive system are electrically independent. The dual winding motor has a characteristic of cancelling the 6th harmonic produced in the overmodulation drive. However, it loses its characteristic when there is a voltage difference in the two voltage supplies. In this paper, it is proposed to control only the sum of the current during the overmodulation to maintain the characteristic of cancellation even if there is voltage difference in the two voltage supplies. Furthermore, the current difference of the two windings is controlled in the sinusoidal wave region to suppress the deviation of currents and turned off during the overmodulation to reduce 6th harmonic. The maintained characteristic during voltage supply unbalance is confirmed with the experiment.

DOI： 10.1541/ieejjia.21001387

Web of Science

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1109/IECON48115.2021.9589696

Web of Science

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEJ Journal of Industry Applications  

This paper presents an analysis of the maximum torque minimum peak phase current of the dual winding interior permanent magnet motor. Reducing the current contributes to small motor size. The peak phase current to generate the torque is reduced by the cancelation of the torque ripple generated by the two windings. The high harmonic current that does not generate torque ripple in the dual winding motor is analyzed. With the high harmonic current, the minimum peak phase current to generate a predetermined torque is calculated. The experiments were conducted to confirm the reduction of the peak phase current without increasing the torque ripple.

DOI： 10.1541/ieejjia.20000098

Web of Science

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：23rd International Conference on Electrical Machines and Systems, ICEMS 2020  

Looking toward the autonomous driving, redundant motor drive system with two voltage supplies, two inverters, and a dual winding motor is reported recently. The dual winding motor has a characteristic of cancelling the 6th harmonic produced in overmodulation drive. However, it loses its characteristic when there is voltage difference in the two voltage supplies. In this report, it is shown that characteristics of cancellation is maintained even if there is voltage difference in the two voltage supplies when sum of the current is controlled. The maintained characteristics is confirmed with the simulation.

DOI： 10.23919/ICEMS50442.2020.9290790

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：23rd International Conference on Electrical Machines and Systems, ICEMS 2020  

We have proposed position sensorless control of PMSMs with Extended-ElectroMotive Force(EEMF). It is available at overall speed with a single estimator by exciting with speed and signal injection. Therefore, the configuration is simplified, and acceleration/deceleration rate is improved because a controller is not switched to another. Additionally, Extended-EMF also available for the start-up method which uses principle of magnetic saturation. In this paper, we propose the new initial rotor position estimation method using Extended-EMF.

DOI： 10.23919/ICEMS50442.2020.9291103

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：23rd International Conference on Electrical Machines and Systems, ICEMS 2020  

This paper evaluates a torque ripple reduction performance of IPMSMs by model selection of magnetization curves to be compensated for magnetic characteristics. A non-linearity compensation method for magnetic characteristics has been proposed, which is based on simple approximations of the magnetization curve. Therefore, an approximation of the magnetic characteristics suitable for torque ripple reduction was studied and the performance of the proposed method was experimentally evaluated.

DOI： 10.23919/ICEMS50442.2020.9290817

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：23rd International Conference on Electrical Machines and Systems, ICEMS 2020  

PMSM is increasingly used in applications requiring safety, such as electric vehicles. However, in a typical PMSM drive system, just one failure of the sensors causes whole system failure. Then it is focused on the potential to improve the system redundancy by making the sensing system redundant In this paper, we report that the control of a current sensing system made redundant by state estimation techniques can be continued even in the event of a phase current sensor failure.

DOI： 10.23919/ICEMS50442.2020.9290924

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：23rd International Conference on Electrical Machines and Systems, ICEMS 2020  

A novel decoupling control scheme for multiphase machines with multiple three-phase winding sets, for instance, the Dual Three Phase (DTP) machines, is proposed in this paper. This motor has two sets of three phase windings that implemented spatially with 30 electrical degrees. Vector Space Decomposition (VSD) frame and Multiple Stator (MS) frame are well known for its vector control. VSD frame has been applied in many applications due to its clear harmonics mapping and good extensions to multiphase machines. On the other hand, MS frame is more intuitive as to treat two winding sets individually so that the accumulated techniques of three-phase machines can be applied directly. However, this approach was not adopted in high performance drives because its decoupling control methodology is not sufficiently developed to solve its inherent magnetic coupling issue. Therefore, this paper proposed a decoupling control scheme to improve dynamic performance of MS frame, and performance has been evaluated by experimental results.

DOI： 10.23919/ICEMS50442.2020.9290999

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：23rd International Conference on Electrical Machines and Systems, ICEMS 2020  

The rotor position sensorless control of Surface Permanent Magnet Synchronous Motor (SPMSM) at a standstill and in the low-speed region is challenging because the motor has no magnetic saliency. Thus, the paper presents the development of a new rotor position-sensorless estimation method for SPMSM.In the proposed method, thin conductive non-magnetic materials are placed on the rotor surface. When the high-frequency voltage is applied, the eddy current flows through the materials, and the inductance is slightly changed depending on the rotor position. The position estimation from 0 to 360 angles (electrical degrees) where the field-oriented control (FOC) is required for SPMSM is realized using this inductance changes. The experiments show that the initial rotor position estimation error is less than 20 degrees ; thus, the proposed method is very useful.

DOI： 10.23919/ICEMS50442.2020.9291246

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：23rd International Conference on Electrical Machines and Systems, ICEMS 2020  

Position sensorless control of PMSMs is one of the important research object in terms of lowering cost, saving installation space and improvement of reliability. A previous research proposed a method to estimate EEMF(Extended Electromotive Force) excited by signal injection and speed for all speed range and confirmed its performance in EV. In this paper, position sensorless control including overmodulation is implemented to EV and evaluated its performance.

DOI： 10.23919/ICEMS50442.2020.9291125

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：23rd International Conference on Electrical Machines and Systems, ICEMS 2020  

The scope of embedded systems used by multi-core processors is widely applied to various products that require control, such as home appliances, industrial devices, transportation devices, and communication terminals. Model-Base Parallelization technology was proposed towards efficient parallelization to implement a control system in the introduction of multi-core processors. By applying MBP, it is possible to parallelization even details that people are not aware of, but the control system with numerous causal relationships still does not sufficiently utilize multi-core. Therefore, a method of inserting a time-delay is being studied as a method for improving the parallelization of multi-cores.In this paper, We describe the insertion location that improves parallelization and does not affect the control performance by inserting time-delay to implement the vector control system of PMSM on multi-core efficiently.

DOI： 10.23919/ICEMS50442.2020.9290965

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：IEEJ Transactions on Industry Applications  

This paper describes the design method for Model Predictive Control (MPC) that is suitable for current control systems of Permanent Magnet Synchronous Motor (PMSM). A current control system based on MPC predicts future current behaviors for considerable input voltage and determines the optimum input voltage by evaluating these behaviors. Conventional MPC sets the cost function, making it effective for several control purposes. However, the suitability of the search space of conventional MPC has not been discussed and its achievable performance was limited. In this paper, we consider an appropriate search space for current control system of PMSM by referring to existing modulation methods and inverter operation. Then, we propose new MPC that satisfies that search space and show that the proposed MPC can usage from a linear region to a square-wave region by the appropriate search space.

DOI： 10.1541/ieejias.140.793

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Proceedings - 2020 IEEE 2nd Global Power, Energy and Communication Conference, GPECOM 2020  

This study presents an angular position control strategy for servo brake motion of an electric motor based on a finite control set-model predictive control (FCS-MPC) with a voltage smoother. In the proposed control scheme, the controller predicts the future current, speed and angular position with a finite set of smoothed voltages and outputs the optimal smoothed voltage by using pulse width modulation (PWM). Smoothed voltages effectively reduce current ripple, which results in less parasitic oscillations of the angular position while tracking the reference target. The simulated and experimental results obtained with a permanent magnet synchronous motor (PMSM), fed by a 2-level 3-phase voltage source inverter, show that the proposed method has both excellent performance of current ripple reduction and excellent dynamic performance in servo brake motion.

DOI： 10.1109/GPECOM49333.2020.9247941

Scopus

Language：Japanese   Publishing type：Research paper (international conference proceedings)   Publisher：IECON Proceedings (Industrial Electronics Conference)  

DOI： 10.1109/IECON43393.2020.9254577

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Last author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Last author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEJ Transactions on Industry Applications  

Extended electromotive force (EEMF) estimation method is a representative method used for position sensorless control of PMSM in the middle/high speed range. EEMF enables position estimation by utilizing back-EMF and the saliency of inductance. The amplitude of EEMF is adjusted to maintain it above a certain voltage by using a signal injection, regardless of the rotor speed. Thus, EEMF can be used as a single position estimator to estimate overall speed range. Based on the validation of a EEMF control performance and a parameter sensitivity analysis, this paper presents a position sensorless control system configured with a single position estimator from startup to middle/high speed. The necessary adjustment parameter and control performance of the actual machine are also presented.

DOI： 10.1541/ieejias.140.589

Scopus

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEJ Transactions on Industry Applications  

This paper proposes a method to design the search space of Model Predictive Control (MPC) for improving the steady current control performance of Permanent Magnet Synchronous Motor (PMSM) current control system. A current control system based on MPC predicts the future current behaviors for considerable input voltage and determines the optimum input voltage by evaluating these behaviors. However, the basic MPC has inferior steady current control performance depending on the operating points. This is because the search space of basic MPC represented by voltage vectors is not suitable appropriate for PMSM current control. To overcome this problem, we consider difference of search space of basic MPC and current vector control with a modulator such as Pulse Width Modulation (PWM) or Space Vector Modulation (SVM) and clarify the necessary search space for improving the steady current control performance. Then we propose a design method for the search space, and through experimentation, we show that proposed design method can improve the steady current control performance.

DOI： 10.1541/ieejias.140.468

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：2019 IEEE 4th International Future Energy Electronics Conference, IFEEC 2019  

Synchronous reluctance motors (SynRMs) have attracted much attention because they do not require magnets. Position sensorless control of SynRMs at low speeds is necessary, and several methods have been proposed in this regard. A new position sensorless control method for SynRMs operating in the very low-speed region is proposed. This approach superimposes a high-frequency current with a small and constant amplitude and a constant frequency to the torque current for driving the SynRMs, by using a high-frequency current control system. It has been shown that robust position sensorless control against inductance variations can be realized using this proposed method. In the position sensorless control method based on a superimposing signal, the current should be small. Therefore, in this paper, the capability of the presented approach to achieve a minimum constant amplitude of the high-frequency current is investigated. The experimental results indicate that the proposed method is a feasible one as position sensorless control of SynRMs in very-low speed region even if the superimposed current has a minimum constant amplitude.

DOI： 10.1109/IFEEC47410.2019.9014679

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：2019 IEEE 4th International Future Energy Electronics Conference, IFEEC 2019  

A flux model that can easily achieve both maximum torque per ampere (MTPA) control and position sensorless control of interior permanent magnet synchronous motors (IPMSMs), is proposed herein. Flux is proposed to be estimated using a full-order observer whose pole assignment is difficult because the order of the error equations of the observer becomes four, and the pole assignment of the full-order observer is proposed. This pole assignment of the full-order observer, in which robust flux estimation against velocity estimation error become possible, is obtained by solving a ?-positive real problem and a H8 control problem. Herein, the experimental result of the position sensorless control of IPMSMs indicates that the proposed pole assignment of the full-order observer is highly useful and can be used to realize MTPA control.

DOI： 10.1109/IFEEC47410.2019.9014918

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：2019 21st European Conference on Power Electronics and Applications, EPE 2019 ECCE Europe  

In this paper, two types of Extended Electromotive Force (EEMF) models are compared and the difference between the position sensorless control performance of these models are also discussed by mathematical equation and experiments.

DOI： 10.23919/EPE.2019.8915112

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：SAGE Publications  

With increase in the number of elderly people in the Japanese society, traffic accidents caused by elderly driver is considered problematic. The primary factor of the traffic accidents is a reduction in their driving cognitive performance. Therefore, a system that supports the cognitive performance of drivers can greatly contribute in preventing accidents. Recently, the development of devices for visually providing information, such as smart glasses or head up display, is in progress. These devices can provide more effective supporting information for cognitive performance. In this article, we focus on the selection problem of information to be presented for drivers to realize the cognitive support system. It has been reported that the presentation of excessive information to a driver reduces the judgment ability of the driver and makes the information less trustworthy. Thus, indiscriminate presentation of information in the vision of the driver is not an effective cognitive support. Therefore, a mechanism for determining the information to be presented to the driver based on the current driving situation is required. In this study, the object that contributes to execution of avoidance driving operation is regarded as the object that drivers must recognize and present for drivers. This object is called as contributing object. In this article, we propose a method that selects contributing objects among the appeared objects on the current driving scene. The proposed method expresses the relation between the time series change of an appeared object and avoidance operation of the driver by a mathematical model. This model can predict execution timing of avoidance driving operation and estimate contributing object based on the prediction result of driving operation. This model named as contributing model consisted of multi-hidden Markov models. Hidden Markov model is time series probabilistic model with high readability. This is because that model parameters express the probabilistic distribution and its statistics. Therefore, the characteristics of contributing model are that it enables the designer to understand the basis for the output decision. In this article, we evaluated detection accuracy of contributing object based on the proposed method, and readability of contributing model through several experiments. According to the results of these experiments, high detection accuracy of contributing object was confirmed. Moreover, it was confirmed that the basis of detected contributing object judgment can be understood from contributing model.

DOI： 10.1177/1729881419876794

Web of Science

Scopus

Other Link： http://journals.sagepub.com/doi/full-xml/10.1177/1729881419876794

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：2019 21st European Conference on Power Electronics and Applications, EPE 2019 ECCE Europe  

We present the redefined Extended EMF, which is proportional to not only rotor speed but also high frequency injected signal. We propose smooth and simple overall speed range position estimation by only using the redefined Extended EMF without switching control method at all.

DOI： 10.23919/EPE.2019.8915377

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：2019 22nd International Conference on Electrical Machines and Systems, ICEMS 2019  

With the introduction of multi-core processors, high performance of the control system has become possible. However, the use of multicore is not enough because parallelization is difficult in systems with sequential algorithms, such as motor current control systems. This paper describes the utilization of time-delay to improve parallelism in multi-core implementations of motor control systems. In addition, we propose a method of analyzing and evaluating the effect of time-delay on the control performance according to the insertion location.

DOI： 10.1109/ICEMS.2019.8921506

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：2019 22nd International Conference on Electrical Machines and Systems, ICEMS 2019  

Along with the expansion of applic tions of PMSM, safety is required for PMSM drive systems. One of the concerns about the safety of the PMSM drive system is sensor failures. In this regard, we aim to make sensor systems redundant and improve fail-safe by using state estimation techniques. In this paper, propose a current control system of PMSM with sensor failsafe by utilizing the techniques and verify some fail-safe performance of the methods in simulation and experiment.

DOI： 10.1109/ICEMS.2019.8921898

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Last author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE International Symposium on Industrial Electronics  

In order to assist cognitive of driver, it is effective for driver to teach the objects that he should recognize in a visual way. However, it is expected that too much information is provided for a driver from the system and it cause him distraction. Therefore, information presentation without exaggeration and without omission is demanded for assistant system. In this paper, it is assumed that the objects which contribute to driver's braking operation should be presented to him. However, these objects changes according to the facing driving situation. Therefore, a selection method of these objects in the appeared objects model is desired. In this paper, a quantification method of contributing degree to braking operation is proposed to select object that system should present. In this method, the degree of contributing to braking operation is calculated based on a driving behavior model. This model express the relationship between the braking operation and time series features of the object that contributes to braking operation. Therefore, in this paper, the modeling method is also proposed.In the experiment, the modeled time series features of the objects that contribute to braking operation was evaluated based on the propose modeling method. Moreover, the calculated degree of contributing to braking operation based on the proposed method was evaluated by using driving simulator. As the results, it was confirmed that high detection accuracy of object that contributes to braking operation was confirmed.

DOI： 10.1109/ISIE.2019.8781518

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/TIE.2018.2851995

Open Access

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Scopus

Authorship：Last author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/eej.23202

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/eej.23198

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/eej.23175

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Authorship：Last author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.6113/JPE.2019.19.1.119

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical Engineers of Japan  

There are many mathematical models for the position sensorless control of permanent magnet synchronous motors (PMSMs), and various position sensorless control methods have already proposed. However, it is necessary to select a control model according to the objective from characteristics of the EMF phase and the robustness against to the motor parameters. An Imaginary Electromotive Force (IEMF) expression can clarify the differences of these models. This paper discusses the characteristics of each model including the Extended Electromotive Force model for position sensorless control that can be applied to the standstill / low speed range from the middle / high speed range. Finally, we show that this IEMF expression is extremely useful in discussing and designing characteristics of the control models of PMSMs.

DOI： 10.1541/ieejias.139.1

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEJ Transactions on Electronics, Information and Systems  

In order to make a multi-joint wearable robot for assisting an user's motions on whole body trunk, this paper discusses the usefulness of control with contact force distribution between user and robot for ensuring the safety of the user. To ensure the safety with wearable assistive robots being different structure from the assisting part of the user, sensing and controlling contact force distribution applying to the user is desired. By utilizing the tactile pressure sensors on the robot's surface, the robot can measure physical contact force distribution as pressure distribution. In this paper, a control methodology based on general impedance control system with pressure distribution is presented. Then, the methodology is confirmed possibility to improve safety compared with conventional torque-base control methodology. In some basically simulations, the proposed control system can reduce power of maximum contact force applying to the user, indicating usability of contact force distribution information for improving safety of assist robots with different motions from assisting parts of the user.

DOI： 10.1541/ieejeiss.139.1325

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEJ Transactions on Electronics, Information and Systems  

We have proposed a localization method of an autonomous mobile robot using multiple sensor information in order to realize robust localization. This method is based on Particle Filter, and bias probability distributions are detected and eliminated before integration of probability distributions for localization. However, the calculation cost is enormous because it is proportional to the number of sensors and particles. In order to reduce the calculation cost for localization, we propose a new localization method using the reliability map of sensor information which is generated based on selection results of sensor information in the previous method in this paper. The usefulness of the proposed method is discussed with some experimental results with a real robot in various real environments.

DOI： 10.1541/ieejeiss.139.1389

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：IEEJ Transactions on Industry Applications  

This paper describes a new discrete-time PMSM model for the discrete design of current vector control systems. The discrete design of current control system minimizes the discretization error and improves the current control performance at the sampling point. The conventional PMSM model discretization method presumes that park transformation runs continuously. When the sampling frequency is considerably lower than the fundamental electric frequency, this assumption is invalid and the control performance will degrade due to modeling error. In this paper, the authors propose a method of PMSM model discretization considering discrete-time park transformation and design an additional cross-coupling compensator for the proposed model. The experimetntation results demonstrate the effectiveness of the proposed model.

DOI： 10.1541/ieejias.139.637

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Language：English   Publishing type：Research paper (scientific journal)  

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DOI： DOI: 10.1177/1729881419876794

Language：English   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEJ Transactions on Industry Applications  

This paper presents signal conditions taking motor efficiency into account for position sensorless control of interior permanent magnet synchronous motors (IPMSMs). Signal injection is necessary for position estimation based on an extended electromotive force (EEMF) model at standstill and low speeds. We have proposed a maximum torque control reference frame and the EEMF model suitable for signal injection, and we executed sensorless control in the entire driving area. However, its effects on motor efficiency have not been evaluated in the previous study. Therefore, in this paper, we optimize the amplitude, phase, and frequency of signal current. Moreover, we applied a signal current amplitude adjusting method. This method makes the signal current amplitude minimum based on the EEMF. As a result, we can maintain constant efficiency including copper loss and other losses of the motor, regardless of the signal frequency. The signal frequency can be freely selected in terms of the motor efficiency, so that the proposed method can improve the flexibility to design the injection signals for the position sensorless control of the IPMSMs.

DOI： 10.1541/ieejias.139.824

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEJ Transactions on Industry Applications  

Global warming and the risk of depletion of fossil fuels are global concerns. The demand for environmental performance of automobiles is becoming severer year by year. In this regard, automotive manufacturers have designed BEVs, PHVs, HEVs and FCVs to meet CO2 regulation. This report presents the recent technological trends related to the main components of electrical vehicles.

DOI： 10.1541/ieejias.139.535

Scopus

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Proceedings: IECON 2018 - 44th Annual Conference of the IEEE Industrial Electronics Society  

Sensorless control has become a popular research area for ac drives. However, most of the works are attributed to conventional three-phase drives. Given that applications of multiphase machines keep spreading, studies of position sensorless for them are necessary. For the object in this paper, some studies for sensorless control in middle/high speed region are reported. To accomplish a full-speed range sensorless control, a study about the standstill/low speed sensorless control of the target motor is proposed in this paper. Particularly, conventional signal injection methods utilized in three-phase ac drives meet a new issue caused by the inner magnetic couplings of the system when applying to the object in this paper. It may lead to failure of sensorless control and torque ripple enlargement. Therefore, analyses to solve the issue become the main interest of this paper, simulation results are demonstrated in the last section.

DOI： 10.1109/IECON.2018.8591145

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Proceedings: IECON 2018 - 44th Annual Conference of the IEEE Industrial Electronics Society  

This paper evaluates our measuring position determination method of Unmanned Aerial Vehicles (UAVs) for automatic visual inspection through an experimentation in real world. This method is under the assumption that the 3D model of a target facility, required accuracy of gathering data and specs of instruments are given. The triangular polygons for shape description of the 3D model are reconstructed for measurement and the measuring positions: the waypoints that an UAV travels to gather the accurate data of the target facility efficiently are calculated systematically. For basic evaluation of this method, we conducted an experimentation in real world. The measuring positions were calculated for an actual target and a camera. An experimenter brought a camera to the measuring positions and gathered image data. This experimentation result showed the effectivity of the method.

DOI： 10.1109/IECON.2018.8591270

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Proceedings: IECON 2018 - 44th Annual Conference of the IEEE Industrial Electronics Society  

To realize automatic inspections for infrastructure facilities by an Unmanned Aerial Vehicle (UAV), improvement of localization performance is needed. Especially, automatic flight does not work in environments near facilities such as under the bridge because GNSS signals does not reach the UAV. We research a localization system using subsidiary UAVs that assist localization of an inspection UAV (main UAV). In this system, the positioning of the subsidiary UAVs is important to correctly complement the position information of the main UAV. In this paper, as the first stage of research, we consider a path of a single subsidiary UAV using preliminary information: the 3D geometrical data of a target facility, the inspection path of the main UAV, and the arrangement of GNSS satellites during the inspection. A simple simulation shows that the localization of the main UAV does not collapse through the whole path under the evaluation of the GNSS positioning precision of each UAV.

DOI： 10.1109/IECON.2018.8592710

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：2018 15th International Conference on Control, Automation, Robotics and Vision, ICARCV 2018  

To improve safety of wearable assist robots, the authors make a prototype wearable robot suitable for the contact force distribution feedback control system. Because wearable assist robots contact the user and apply force directly, ensuring safety of the user is most important. In order to improve safety from the aspect of control, a contact force distribution feedback control system has been researched. The system controls contact force between the user and a robot directly. Although the system validated in principal with a simple robot model on simulation, validation with an actual robot has not done yet. There are no wearable robots measurable the contact force distribution with user. In order to measure the contact force distribution for the control system, two points: Measurement reproducibility and measurement as distribution, are necessary. In this paper, a prototype robot that satisfies the two points is made. The robot is confirmed to have the two points necessary for the system by measurement experiment.

DOI： 10.1109/ICARCV.2018.8581233

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：2018 20th European Conference on Power Electronics and Applications, EPE 2018 ECCE Europe  

This paper discusses the initial position error convergence of position sensorless control of Permanent Magnet Synchronous Motor by using Extended Electromotive Force excited by signal injection when motor parameter error exists, and verify that by experimental results.

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：2018 20th European Conference on Power Electronics and Applications, EPE 2018 ECCE Europe  

This paper proposes a current control system which deactivates an antiwindup control for improving the control performance of PMSMs in the overmodulation region of an inverter. Control performance of PMSMs cannot be improved appropriately without countermeasure against harmonic components which are generated in this region. Deactivating of antiwindup control can be a countermeasure against these harmonic components, however deterioration of current responses due to windup phenomenon is unavoidable. Proposed control system reduces the deterioration of torque response due to windup phenomenon by deactivating the antiwindup control only in the steady state in the overmodulation region. Proposed control system have confirmed that it can achieve fast torque response and high power operation by simple algorithm without motor parameters.

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：2018 20th European Conference on Power Electronics and Applications, EPE 2018 ECCE Europe  

This paper presents a position sensorless control scheme based on pattern matching method for high power density Interior Permanent Magnet Synchronous Motors (IPMSMs) that have non-sinusoidal inductance spatial distribution. The pattern matching method achieves the closed loop position sensorless control under heavy load condition. However, atypical position control control errors are generated. To improve the position control errors, a new pattern matching method is proposed in this paper. The proposed method estimates the rotor position by using multiple template data sets which created while changing a current phase. Through experimental results, the effectiveness of the proposed method is presented.

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Institute of Electrical and Electronics Engineers Inc.  

Several position sensorless control methods of interior permanent magnet synchronous motors (IPMSMs) using observers have been proposed. In the case of full-order observers, these designs are difficult because the order of the error equations of observers becomes an order of four. In this paper, to realize the position sensorless control of IPMSMs, a design method for full-order observers based on the extended electromotive force (EEMF) is proposed, and the pole assignment of the proposed observer is studied. Experimental results of the position sensorless control of an IPMSM show the usefulness of this proposed design method for the full-order observer compared to the case where poles are merely assigned on the left half plane.

DOI： 10.1109/ICELMACH.2018.8506894

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：2018 International Power Electronics Conference, IPEC-Niigata - ECCE Asia 2018  

In this paper, we summarize a method of applying a maximum torque control reference frame to IPMSMs with large influence of magnetic saturation. Conventionally, a formula based on the torque equation with motor parameters of IPMSMs has been used to calculate the phase angle of the maximum torque control reference frame. However, the equation is greatly affected by inductance variation due to magnetic saturation. Therefore, we propose the phase angle determination method based on a torque map. The method is not affected by inductance variation because it does not need motor parameters directly. Performance improvement is confirmed by simulation and actual machine experiments.

DOI： 10.23919/IPEC.2018.8507807

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：2018 International Power Electronics Conference, IPEC-Niigata - ECCE Asia 2018  

This paper proposes a new V/f control method for permanent magnetic synchronous motors (PMSM) without position sensor. The proposed method uses state feedback control based on a n-t coordinate system. The t-axis is a tangent line of a constant voltage ellipse, and the n-axis is a normal line of the ellipse. The t-axis current is utilized to keep the system poles in the stable plane in low speed of motor and to achieve high stability.

DOI： 10.23919/IPEC.2018.8507624

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：2018 International Power Electronics Conference, IPEC-Niigata - ECCE Asia 2018  

This paper describes a new discrete-time PMSM model for discrete design of current vector control system. Discrete design of current control system is a via discrete-time PMSM model. This controller minimizes dis-cretization error and ensure perfect control performance at sampling point. Conventional discretization method presume park transformation runs continuously. When sampling frequency is too lower than fundamental electric frequency, this assumption is invalid and control performance will degrade by modeling error. In this paper, authors propose the method of PMSM model discretization in consideration of discrete-time park transformation. Simulation results show the effectiveness of proposed model.

DOI： 10.23919/IPEC.2018.8507948

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：2018 International Power Electronics Conference, IPEC-Niigata - ECCE Asia 2018  

We have proposed Model predictive Control which can manage the voltage phase resolution. This method decides the optimum permutation of voltage vector by predicting current behaviors for all permutations and evaluating behaviors. Our method can realize same steady current control performance of FOC, however, there is the issue which calculation amount become very huge. In this paper, we propose new search algorithm of our MPC which can reduce calculation amount. In Propose algorithm, we take a notice that control set of our MPC can be classified by type and number of the voltage vector. Calculation amount is reduced by selecting search space depending on operation points. We show that new algorithm can be greatly reduced calculation amount while keeping steady current control performance.

DOI： 10.23919/IPEC.2018.8507886

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：2018 International Power Electronics Conference, IPEC-Niigata - ECCE Asia 2018  

Although the virtual space PWM and the dual wave modulation (DWM) method can eliminate the low frequency neutral point potential (NPP) fluctuation, which appears in some NPP control based on the nearest three vector PWM essentially, they will increase the switching frequency and fade the control ability of the NPP drift problem. In this paper, a novel multiple degree of freedom based NPP control with the strong control ability of low frequency NPP fluctuation and NPP drift problem is proposed for three level converter. The traditional DWM method sacrifices many control domains of neutral point current (io) to keep io zero, by setting the zero sequence voltage to an appropriate value. On the contrary, the proposed method introduces three degree of freedom to control the NPP, which makes it have the largest NPP control domains. The comparison on the control domains of io for DMW method and proposed method is discussed at first. Then, some simulation are also carried out to verify the correctness and effectiveness of proposed method.

DOI： 10.23919/IPEC.2018.8507804

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE/ASME International Conference on Advanced Intelligent Mechatronics, AIM  

This paper discusses a robust localization method that uses particle filtering. A particle filter can suppress the influence of temporary noise on a sensor based on past sensor data. However, localization fails when a sensor is affected by noise that lasts for several minutes even when using a particle filter. We have previously proposed a majority rule-based sensor fusion system that removes sensors affected by such constant noise. To date, we have conducted some experiments to evaluate the effectiveness of this system without particle filter. In this paper, we experimentally confirm the effectiveness of this system with particle filtering. The results show that the proposed system reduces position errors in part of the environment.

DOI： 10.1109/AIM.2018.8452415

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE International Symposium on Industrial Electronics  

Traffic accidents caused by elderly drivers have become an important social issue in Japan. The primary factor of traffic accidents by elderly drivers is a reduction in their driving skill. In this case, in order to assist operation of driver whose driving skill is reduced, the system must be able to evaluate his driving behavior skill. In this paper, we propose a evaluation method of driver's driving skill. Here, coincident timing skill is focused on. A driver decides an execution timing of his operation based on prediction of time series change of situation around him. When execution timing of operation of the driver has the widely variability in spite of the same driving scene, it is considered that he have a reduced ability to drive vehicle. This magnitude of variability of execution timing of operation of driver is defined as coincident timing skill of the driver. In this paper, in order to evaluate this coincident timing skill, a driving behavior modeling technique is applied. Driving behavior model is used to predict driver's operation. And we have proposed a driving behavior modeling method to predict driver's operation. In our method, the execution timing of driver's operation is modeled by probability model. Therefore, our model has the potential to evaluate the driver's coincident timing skill by analyzing this probability model. According to the above viewpoint, we propose a evaluation method of coincident timing skill based on our driving behavior model. In the experiment, the driving behavior models of brake operation with difference execution timing are generated. Then, the results that the difference of each coincident timing skills is evaluated quantitatively based on the proposed method are shown.

DOI： 10.1109/ISIE.2018.8433732

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ITEC Asia-Pacific 2018 - 2018 IEEE Transportation Electrification Conference and Expo, Asia-Pacific: E-Mobility: A Journey from Now and Beyond  

In order to reduce switching frequency and achieve maximum utilization rate of DC-link voltage, traditional voltage phase controller realizes six-step operation via an integrator in SPMSM drives. However, it is not able to achieve a good torque performance in steady state and transient state at the same time, due to the integral saturation problem and bandwidth limit of the integrator. By analyzing the effects of the 6/12-order torque ripple, this paper claims that the 6/12-order torque ripple derived from six-step operation directly limits the bandwidth of control system. Thus, a model-based voltage phase controller is proposed in this paper to replace the integrator. The proposed method can obtain a faster torque response in transient state as well as a good torque performance in steady state. Finally, some simulation results are also given to verify the correctness and feasibility of proposed method.

DOI： 10.1109/ITEC-AP.2018.8432597

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：John Wiley and Sons Inc.  

To realize the neutral point potential (NPP) control for three-level neutral-point-clamped (TL-NPC) converters, a novel NPP control based on the search optimization method of the two degrees of freedom is proposed in this paper. It can overcome the low-frequency NPP fluctuation problem that appears under nearest-three-vector pulse width modulation (PWM)-based NPP control under some operating conditions. Although the traditional dual modulation wave method can also solve the low-frequency NPP problem, the zero-sequence voltage is limited under this modulation. It decreases the control domain of the neutral point current (io), which causes serious NPP drift problem especially in some special operating conditions, such as a long dead time, a strong asymmetrical load, or serious switch device inconsistency. The proposed method can expand the control domain of io by defining a new degree of freedom, thus lifting the limits of the zero-sequence voltage and searching for the optimal two degrees of freedom. The wider control domain of io corresponds to a stronger NPP control ability. Experiments are carried out finally to prove the merits of the proposed method, by comparing the switching frequency, the NPP control speed, and the output performance. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley &amp
Sons, Inc.

DOI： 10.1002/tee.22683

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Publishing type：Research paper (international conference proceedings)   Publisher：Proceedings of the IEEE International Conference on Industrial Technology  

DOI： 10.1109/ICIT.2018.8352247

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Institute of Electrical and Electronics Engineers Inc.  

This paper presents the filter setting for improving the current control performance of IPMSMs in overmodulation region of inverter. To operate IPMSMs in the overmodulation region, it is necessary to deal with harmonic components. Generally, harmonics suppression method based on harmonics current model is utilized to deal with these components, however, it requires accurate motor parameters. In this paper, Band Stop Filter is utilized to suppress the harmonic components, and weight averaging method is applied to improve the current responses, without any motor parameter. Simulation results are demonstrated to show the current control performance and the operation range of proposed method.

DOI： 10.1109/PEDS.2017.8289245

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Institute of Electrical and Electronics Engineers Inc.  

The Extended Electromotive Force(EEMF) has a high potential because that the model enables position estimation by utilizing not only electromotive force but also saliency of inductance. In particular, the EEMF consists of two components, excited by rotor speed and high-frequency signal injection. The characteristic of EEMF excited by speed has been proposed sufficiently. This paper describes analysis of robustness of parameter error in two types of Extended Electromotive Force (EEMF) exited by high frequency signal injection for position sensorless control. Finally, formula evaluation indicates that each EEMF model has different robustness of parameter error.

DOI： 10.1109/PEDS.2017.8289235

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：2017 Asian Control Conference, ASCC 2017  

The authors aim for safe assistance by feedback control of the contact force in the wearable robot. Securing safety for users is of utmost importance for wearable robots. For safe assistance of complex body parts such as the torso, the robot is desirable to be able to sense the contact force: the force applied to the human body by the robot. The authors have been studying robots sensing contact force distribution from tactile sensors on the robot surface as pressure distribution. The robot is controlled to reduce superfluous contact force. In this paper, a new control method, contact force distribution predictive control system, is proposed. This method predicts the contact force distribution of the next step from the current link positions and contact force distribution of the robot. The robot is controlled so as to realize the optimum contact force distribution. The proposed method is compared with the conventional control based on joint torque and the effectiveness of our method is verified.

DOI： 10.1109/ASCC.2017.8287372

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley-Liss Inc.  

With an increase in the elderly population, traffic accidents caused by elderly drivers have become an important social issue in Japan. The primary factor of traffic accidents by elderly drivers is a reduction in their driving skill. Therefore, elderly drivers are required by law to conduct regularly a driving aptitude test in Japan. If the driving skill of the driver is inadequacy, he is subject to punishment, such as driver license revoked. However, there is not appropriate evaluation index of driving skill. We have proposed a modeling method of driving behavior to support one. Proposed driving behavior model is generated based on the actual driving data of driver, and the generated model has some kind of habit and pattern of the driver. Therefore, it is considered that it is possible to evaluate driving skill of a driver by analyzing the generated model. According this reason, we aim to propose a modeling method of driving behavior to evaluate driving skill. Here, a coincident timing skill of driver is focused as a driving skill. In the case of driving behavior, the execution timing of driving operations is decided based on the prediction of subsequent change of the outside environment information. The accuracy of this decided execution timing of operation depend on the above prediction is called as the coincident timing skill. In the proposed model, the causality between the situation around a person and operation of driver is modeled by Hidden Markov Model, and timing probability distribution is added to Hidden Markov Model in order to evaluate this coincident timing skill. The timing probability distribution expresses the execution timing of next operation of driver. Therefore, it is possible to detect the information of the coincident timing skill of driver from the timing probability distribution. In the experiment, the controller operation of a radio controlled vehicle is modeled by the proposed method, and the usefulness of the proposed model is examined through some experimental results.

DOI： 10.1002/ecj.12049

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：31st International Electric Vehicle Symposium and Exhibition, EVS 2018 and International Electric Vehicle Technology Conference 2018, EVTeC 2018  

In this paper, a position sensorless control method for the Wound-field Synchronous Motor with Double Threephase wound stator(D-WFSM) in middle or high speed driving is proposed. Extended electromotive force observer used commonly for PMSMs is selected for the target motor’s position sensorless control method. However, due to the voltage phase control method, the estimated position error contains high frequency components. It would deteriorate the position estimation. Therefore, in this paper, a new extended electromotive force model for two-set motors is proposed. Then, the effectiveness of the proposed method is verified through simulation.

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：IEEJ Transactions on Industry Applications  

Sensorless control based on a pattern matching method is proposed for interior permanent magnet synchronous motors (IPMSMs), which have non-sinusoidal inductance spatial distribution at a standstill and very low speed regions. By using the pattern matching method, closed-loop-position sensorless control is possible for IPMSMs even under the heavy load condition, but atypical position error occurs. A previous study examined why position control errors are generated in the pattern matching method. This paper presents three improvement methods for the position control error by considering the cause of the position control error. In addition, characteristics of each proposed method are clearly explained, and their effectiveness is presented by simulation and experimental results.

DOI： 10.1541/ieejias.138.902

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEJ Transactions on Industry Applications  

This paper proposes a torque control method for interior permanent magnet synchronous motors (IPMSMs). The proposed method uses state feedback control based on a new n-t coordinate system and controls the voltage amplitude and phase based on the coordinate system. The t-axis is a tangent line of the constant voltage ellipse, and the n-axis is a normal line of the ellipse. The n-axis current is utilized to place the poles of the transfer function at the desired position and reduce the mutual coupling between the voltage amplitude controller and phase controller. The proposed method realizes a high torque response even under parameter variation for the linear range and over-modulation range of the inverter, including a six-step mode. The effectiveness of the proposed method was verified by simulation and experimental results.

DOI： 10.1541/ieejias.138.563

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical Engineers of Japan  

A sensorless control based on a pattern matching method is proposed for interior permanent magnet synchronous motors which have non-sinusoidal inductance spatial distribution, at a standstill and in very-low-speed regions. A previous study indicated that closed-loop-position sensorless control can be achieved under heavy load conditions. However, position control errors are generated at atypical rotor positions, and the reason for this has not been clarified. Moreover, there remains an issue in which this position error cannot be perceived before position sensorless control is carried out. This study examines why position control errors are generated in the pattern matching method. Furthermore, an evaluation method that estimates position control error in advance is proposed using the clarified mechanism of position error generation. The effectiveness of the proposed method is demonstrated by comparing experimental and evaluation results.

DOI： 10.1541/ieejjia.7.73

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEJ Transactions on Industry Applications  

This paper proposes a filter design for improving the control performance of the current control system of Permanent Magnet Synchronous Motors (PMSMs) using the overmodulation region of an inverter. The control performance of a vector control system for PMSMs using the overmodulation region of an inverter can be improved by suppressing harmonic components that are generated in this region. This paper utilizes Band Elimination Filter (BEF) to eliminate harmonic components; however, unsuitable BEF setting leads to generation of large current oscillation at the resonant frequency of current feedback loop with BEF. In order to deal with these problems, the proposed filter design focuses on gain setting at the cutoff frequency of BEF. The proposed filter design can prevent the generation of current oscillation at the resonant frequency of the system, and can improve current control performance without complex adjustments. Simulations and experiments are carried out to show the effectiveness of the proposed BEF setting.

DOI： 10.1541/ieejias.138.884

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEJ Transactions on Industry Applications  

This paper proposes a new V/f control method for permanent magnetic synchronous motors (PMSMs) without a position sensor. The proposed method uses state feedback control based on an n-t coordinate system, and controls rotational speed and the voltage amplitude. The t-axis is a tangent line of a constant voltage ellipse, and the n-axis is a normal line of the ellipse. The t-axis current is utilized to place the poles of the transfer function at the desired position at low speed and high speed conditions. The effectiveness of the proposed method was verified by simulation and experimental results.

DOI： 10.1541/ieejias.138.911

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)  

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)  

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Proceedings IECON 2017 - 43rd Annual Conference of the IEEE Industrial Electronics Society  

For the discussion about the neutral point potential (NPP) control of single phase three-level rectifiers, most of the methods solve the NPP problem by adjusting the zero-sequence voltage under symmetrical load conditions. However, when one phase voltage reaches to the maximum voltage, the other phase voltage goes to the minimal voltage. As a result, the NPP control ability is limited since there is no chosen zero-sequence voltage when the modulation ratio is close to 1. It can not be suitable for some strong asymmetrical load applications, in which two DC-link capacitors are used to drive different loads separately. In this paper, a dual-degrees of freedom based PWM is proposed, which can enhance the NPP control ability for single phase three level rectifiers. Introducing a new degree of freedom, the proposed method has more choices for the NPP control. It can decrease the NPP fluctuation under the strong asymmetrical load conditions, compared with the traditional PWM methods. The simulation results ratify the correctness and feasibility of the proposed PWM method finally.

DOI： 10.1109/IECON.2017.8216093

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1109/SII.2017.8279210

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：2017 19th European Conference on Power Electronics and Applications, EPE 2017 ECCE Europe  

Even though the neutral point potential (NPP) balance problem of three-level neutral-point-clamped (NPC) converters can be solved by the traditional methods based on nearest-three-vectors (NTV) PWM, a low frequency fluctuation in the NPP will appear, which makes the capacitor reduction become hard. The dual modulation waves method is used to overcome the low frequency fluctuation, but it is an open-loop way, which will cause the drift voltage problem of the NPP and increase the switching frequency. Moreover, the control ability of the neutral point current is limited since the zero-sequence voltage is fixed. By removing the limit of the zero-sequence voltage and introducing a new degree of freedom, a novel NPP control of three-level NPC converters based on the search optimization is proposed in this paper. Fuzzing the boundary between the NTV-PWM and the dual modulation waves method, the proposed method realizes two modulations by a unified way. It can solve the low frequency fluctuation problem, reduce the switching frequency and extend the control ability of the neutral point current simultaneously by choosing the optimal dual degrees of freedom. Comparing the NTV-PWM, the dual modulation waves method and the proposed method, the simulation results verify the correctness and effectiveness of the proposed method.

DOI： 10.23919/EPE17ECCEEurope.2017.8098930

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：2017 19th European Conference on Power Electronics and Applications, EPE 2017 ECCE Europe  

This paper describes sensitivity analysis to q-axis inductance variation of the position estimation using Extended Electromitive Force (EEMF) excited by High Frequency (HF) signal injection based on the mathematical formula evaluation, and it shows that the influence on the q-axis inductance variation is very small. Finally, experimental results indicate that position estimation can be performed well without any q-axis inductance information.

DOI： 10.23919/EPE17ECCEEurope.2017.8099118

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：2017 19th European Conference on Power Electronics and Applications, EPE 2017 ECCE Europe  

This paper describes a method of deriving frequency characteristics of PMSM current control system based on Model Predictive Control (MPC). MPC controller predicts the current behavior using the mathematical model of PMSM and directly selects the optimal switch state based on evaluation of these predicted results. So, we have focused the possibility of MPC, which makes it possible to drive machines seamlessly between linear operating region of inverter and the overmodulation operating region. But, MPC is a nonlinear control system, so its frequency characteristics are unknown. In this paper, we derive MPC's frequency characteristic approximately through simulation to realize its frequency domain design.

DOI： 10.23919/EPE17ECCEEurope.2017.8099119

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：2017 19th European Conference on Power Electronics and Applications, EPE 2017 ECCE Europe  

This paper proposes a high response voltage phase torque control method of interior permanent magnet synchronous motors for both linear and over-modulation range including six-step mode. In our proposed method, a new n-t coordinate system is utilized, on which voltage phase and amplitude are controlled responsively and stably.

DOI： 10.23919/EPE17ECCEEurope.2017.8098942

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

This paper presents a novel pattern matching based position sensorless control method for IPMSMs. A target IPMSM for the proposed method is designed such that it has high power and torque density, while also being significantly influenced by magnetic saturation. As previously reported in papers , for IPMSMs, heavy magnetic saturation affects the spatial distribution of phase inductances according to rotor positions. Most position sensorless controls at low speeds typically depend on the assumption that phase inductances have sinusoidal spatial distribution according to rotor positions. Therefore, it is difficult to apply conventional methods to IPMSMs with heavy magnetic saturation. In the proposed method, rotor position is estimated by pattern matching using feature values, so that the phase inductances have unique and reproducible value according to rotor positions. While template data sets are required for the proposed method, the assumption for sinusoidal phase inductances is not. In this paper, the effect of magnetic saturation for position estimation based on conventional methods is discussed in Section 1 and 2. Then, details of the proposed method are shown in Section 3. In Section 4, results of experiments carried out in steady state and transient state are presented. The effectiveness of the proposed method is verified through the experiments.

DOI： 10.1002/eej.23008

Web of Science

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Institute of Electrical and Electronics Engineers Inc.  

Several position sensorless control methods of IPMSMs(Interior Permanent Magnet Synchronous Motors) using the observers have been proposed. In case of the full-order observers, these designs are difficult, because the order of the error equations of the observers becomes four. In this paper, for the position sensorless control of IPMSMs, a design method of the full-order observer based on the extended electromotive force (EEMF) is proposed. The experimental result shows that this design method of full-order observer is very useful.

DOI： 10.1109/ICEMS.2017.8056278

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：2017 20th International Conference on Electrical Machines and Systems, ICEMS 2017  

Even though some methods have been put forward to solve the drift problem and the low frequency fluctuation problem of the neutral point potential (NPP) for three level neutral point clamped converters (TL-NPC), they are all just suitable for SPWM or SVPWM technologies. In some medium/high voltage high power applications, where SHEPWM is utilized to modulate the reference voltages, the drift problem and the low frequency fluctuation problem of the NPP become difficult. The duty cycle of phase voltage waveforms under SHEPWM can't be adjusted after the switching angles were calculated based on the optimal harmonic limits. For the severe low frequency fluctuation of the NPP, a suppression method is raised based on 3-order harmonic amendment in this paper. 3-order harmonic has no effect on the output performances under 3-phase 3-wire systems, but it can regulate the NPP. By analyzing the relationship between the NPP and 3-order harmonic, an optimal 3-order harmonic is determined. Using the optimal 3-order harmonic to calculate the switching angles for SHEPWM, the low frequency fluctuation of the NPP is suppressed obviously, which is important to improve the output performances and to reduce Dc-link capacitors. The simulation is done to verify the correctness and feasibility of proposed method.

DOI： 10.1109/ICEMS.2017.8056223

Scopus

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：2017 20th International Conference on Electrical Machines and Systems, ICEMS 2017  

This paper presents the filter setting for expand the operation range of IPMSMs in overmodulation region of inverter. To operate IPMSMs in the overmodulation region, it is necessary to deal with harmonics components. In this paper BSF is utilized to suppress the harmonic components, and its setting method is mentioned. The operation range in the overmodulation region is expanded appropriately by setting the filter focusing on resonant frequency of the system.

DOI： 10.1109/ICEMS.2017.8056395

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Institute of Electrical and Electronics Engineers Inc.  

Synchronous reluctance motors (SynRMs) have attracted studies, because SynRMs have no magnets in the rotors. The position sensorless control at low speeds of SynRMs is now desired, and several methods have been proposed. In this paper, by using the high-frequency current control system, a new position sensorless control method of SynRMs at low speeds by superimposing high-frequency current whose amplitude is small constant value has been proposed. The experiments show that the proposed method is very useful even if the very low speeds region.

DOI： 10.1109/ICEMS.2017.8055979

Scopus

Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE International Symposium on Industrial Electronics  

Even if the dual modulation waves based neutral-point-potential (NPP) control for three-level converters is able to eliminate the low frequency NPP fluctuation, it just has the natural balancing characters for the NPP. Thus, a compensation strategy is necessary to solve the drift voltage problem of the NPP. The traditional compensators overcome the drift voltage problem by adjusting an offset voltage. Since there is no theoretical basis to determine the gain of the offset voltage, it may cause the over-adjustment. It is also difficult to master the law of the output waveform adjusted by the offset voltage. Given these defects of the traditional compensators, a new compensation factor (CF) is raised and the relationship of the CF, the NPP, the phase current and the Dc-link capacitors is analyzed in this paper. By adjusting the CF in a limit region analyzed in this paper, the drift voltage problem is well solved without over-adjustment. Since it is easy to know the law of the output waveform adjusted by the new CF, it can also decrease the switching frequency and avoid the three level modulation degrading to the two level modulation in some operation conditions. Simulation results verify the correctness and effectiveness of the proposed method.

DOI： 10.1109/ISIE.2017.8001364

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：2017 IEEE 3rd International Future Energy Electronics Conference and ECCE Asia, IFEEC - ECCE Asia 2017  

A pattern matching method for position sensorless control of IPMSMs having non-sinusoidal inductance spatial distribution in standstill and very low speed region has been proposed. In the proposed method, the rotor position is estimated by comparing the phase current derivatives measured in a real-time with those in advanced. The current derivatives are obtained by measuring the phase currents twice at the certain voltage vector of inverter switching. The certain voltage vector not only must be created in all rotor position, but also must continue for at least a minimum time (tmin) to measure the currents twice. However there exists conditions which could not be secured tmin depending on the load current and the rotor position. In previous researches, switching-state phase shift method is utilized in order to create the certain voltage vector by injection high frequency voltage in all rotor position. In this paper, proposed various switching-state phase shift methods are explained and strong and weak points of each method are compared. Furthermore, the effectiveness and remaining issues of each methods are represented by experimental results.

DOI： 10.1109/IFEEC.2017.7992416

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：2017 IEEE 3rd International Future Energy Electronics Conference and ECCE Asia, IFEEC - ECCE Asia 2017  

This paper describes new model predictive control for high performance current control system of PMSM. The current control system based on FCS-MPC decides an inverter output voltage directly by searching. In a principle, this type controller can use not only PWM drive but also overmodulation and square wave drive[1]. However, conventional current control based on FCS-MPC is inferior to PWM modulated PI base control in the steady control performance for the reason of this method that the voltage phase resolution is coarse. The improvement of the voltage phase resolution of FCS-MPC can't realize by the restriction of the equipment. So, we have proposed new model predictive control to improve the voltage phase resolution not depending the limitation of the device[2], [3]. In this paper, we evaluate the characteristics of propose method comparing conventional current control based on FCS-MPC by the simulation and experimentation.

DOI： 10.1109/IFEEC.2017.7992293

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Proceedings of the International Conference on Power Electronics and Drive Systems  

This paper presents a position sensorless control method based on pattern matching method for high power density Interior Permanent Magnet Synchronous Motors (IPMSMs) that have non-sinusoidal inductance spatial distribution. In this paper, a new pattern matching method using feature values measured at zero voltage vector is proposed to improve the position estimation performance. By measuring the feature values at zero voltage vector, the number of feature value used in evaluation function is increased and it is advantageous for position sensorless control performance while keeping the wide operating range. Through experimental results, the effectiveness of the proposed method is presented.

DOI： 10.1109/PEDS.2017.8289201

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Proceedings of the International Conference on Power Electronics and Drive Systems  

We have proposed new Model Predictive Control which can design the voltage phase resolution and average switching frequency independently for improving steady control performance. Our propose method is based on FCS-MPC, the controller decides switching timing of each phase during control period directly by predicting future current behaviors at each prediction period and evaluate each behaviors. Shortening prediction period can improve steady current control performance, however, calculation amounts of prediction become huge and interfere with implementation. So, our method needs understanding the characteristics of voltage phase resolution and the necessary voltage phase resolution in each operation point for realizing a same level steady current control performance of PI base current vector control using PWM. In this paper, we describe the steady current characteristic of the voltage phase resolution of our method.

DOI： 10.1109/PEDS.2017.8289233

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SII 2017 - 2017 IEEE/SICE International Symposium on System Integration  

The authors aim for safe assistance by feedback control of the contact force distribution in wearable robots. Since the wearable robot is in direct contact with the user, safety control is important. In order to improve safety, robot is desirable to be able to be controlled based on contact force: The force applied to the human body by the robot. A control system that feeds back joint torque as contact force has been proposed. However, since the joint torque is the resultant force of the contact force, there is a possibility that the dangerous contact force can not be detected directly. In this paper, the authors propose a new control system based on contact force distribution. The contact force distribution is sensed as pressure distribution by the tactile sensors attached to the robot surface. Impedance control in manipulator was expanded and applied to contact force distribution feedback control. The proposed method is compared with the control based on joint torque and the effectiveness of our method is verified.

DOI： 10.1109/SII.2017.8279340

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

A modeling approach for human action is the focus of this paper. We design a human action model based on the stored data obtained during long-term monitoring of a person. This approach consists of the following two processes. First, several kinds of partial time series data that occur frequently are extracted from the stored data and taken to be human action patterns. Next, the extracted time series data are modeled based on a statistical modeling method such as the hidden Markov model. In this research, we focus on the extraction method for the time series data that occur frequently in the stored data. A person changes his actions according to changes in the situation around him. Moreover, it takes some time for him to perform his action after he recognizes the situation around himself. This time is called the delay time in this paper. A human action model that takes this delay time into consideration leads to greater accuracy in recognition and prediction of human actions based on that action. It is necessary to extract time series data for a situation and an action with the delay time as training data in order to generate the above human action model. In conventional methods, multidimensional time series data are used as the stored data without a distinction between the situation and action data. Also, some partial time series data that occur frequently are extracted from the stored data. Therefore, the delay time is not taken into account. In this paper, we propose a new extraction method for time series data that occur frequently with the time delay taken into consideration. In this method, sets of partial time series data that occur frequently with the delay time are extracted by evaluating the repeatability and similarity between the partial time series data sets with different occurrence frequencies. In the experiment, we extract the interaction motions that occur frequently between two subjects. The utility of the proposed method is examined based on the experimental results.

DOI： 10.1002/ecj.11961

Web of Science

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.9746/sicetr.53.169

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：19th International Conference on Electrical Machines and Systems, ICEMS 2016  

A pattern matching method for position sensorless control of IPMSM with heavy magnetic saturation in standstill and very low speed region has been proposed. The rotor position is estimated by comparing the feature values measured in a real-time with in beforehand. To measure feature values, high frequency signal must be injected. The operation region of pattern matching method is limited by amplitude of injectable signal. This paper presents the operating region that could utilize pattern matching method. Also to expand the operating region, a new signal injection method and matching method are proposed. By using the proposed method, the same sampling time interval for measuring feature values could be obtained even smaller signal is injected.

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical Engineers of Japan  

This study investigates compensation methods for harmonic components to realize PMSM position sensorless control in inverter overmodulation drive. While applying PMSMs as traction motor motors in an EV or HEV, operating PMSM in inverter overmodulation drive is an effective method to widen high-speed drive region of PMSM and achieve fast torque response when voltage saturates because it enable to utilize 27% higher fundamental voltage as compared to linear drive. In addition, position sensorless control is regarded as an important technique for adding a fail-safe function and downsizing of the drive system. However, the harmonic components which are inevitably generated in inverter overmodulation drive have negative effects on closed current control and position estimation systems. The key to realize position sensorless control in inverter overmodulation drive is an appropriate compensation for the harmonic components in the input voltage and input current of a the position estimator. There are several methods to achieve this, and differences in position estimation performance possibly exist among these methods. In this study, the compensation methods for harmonic components in overmodulation drive are compared, and a suitable compensation method for sensorless control is investigated through an experiment.

DOI： 10.1541/ieejjia.6.165

Web of Science

Scopus

Language：English   Publishing type：Research paper (scientific journal)  

Web of Science

Language：English   Publishing type：Research paper (scientific journal)  

Web of Science

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

<p>In this paper, we propose a self-localization method of an autonomous mobile robot using multiple 2D maps generated with information from 3D Lidar. In this method multiple 2D maps are generated with 3D point cloud divided into some groups based on the height from the ground. Then, multiple probability distributions for self-localization are generated with particle filter. The result of self-localization is calculated by selection and integration of the probability distributions based on KL divergence.</p>

DOI： 10.1299/jsmermd.2017.2P2-D02

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

<p>In order to realize automatic inspection for infrastructure facilities using Unmanned Aerial Vehicles(UAVs), improvement robust localization of UAVs is needed. Especially, automatic flight could not be work in environments near facilities such as under the bridges. In this research, localization method is studied based on integration of position information gathering from subsidiary UAVs located in the surroundings of a main UAV. In this paper, as the first stage of this study, probabilistic position estimation model of subsidiary UAVs is modeled and integrated based on joint probability. By simulations with the models, influences of both position estimation errors of subsidiary UAVs and measurement errors of relative position are considered.</p>

DOI： 10.1299/jsmermd.2017.2P2-C02

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Society of Instrument and Control Engineers  

This paper presents a measuring-position-determination method of Unmanned Aerial Vehicles (UAVs) for automatic visual inspection system. In the proposed method, it is assumed that 3D model of the target infrastructure, the specification of measurement and UAV's features are given. Under those assumptions, the measuring positions are calculated considering the accuracy of data. In this paper, the usefulness of the proposed method is examined by a computer simulation assuming visual inspections for several bridges. In the simulation, measuring positions are determined assuming several types of UAVs for each bridge.

DOI： 10.9746/sicetr.53.229

CiNii Books

Language：Japanese   Publishing type：Research paper (other academic)   Publisher：The Japan Society of Mechanical Engineers  

<p>To realize robust localization of mobile robot, it is important to improve method of integrating position information from various sensors whose dependence on environment is different. In the case of probability localization, such as particle filter, simultaneous probability is used. However, when a sensor is affected by huge noises such as multipath of GPS, simultaneous probability is incorrect. The authors have proposed selective sensor fusion system based on similarity of distributions. This paper proposes a new similarity evaluation method analyzing particles sampled from distribution and verifies its effectiveness by real world localization.</p>

DOI： 10.1299/jsmermd.2017.2P2-C01

Language：Japanese   Publishing type：Research paper (other academic)   Publisher：The Japan Society of Mechanical Engineers  

<p>Maintenance of infrastructures is a major problem. In order to streamline it, automation of inspections is researched. For complete automation, the measuring position determination method of inspection machines is necessary. This paper presents a method of measuring position determination using vector quantization for automatic visual inspection systems using Unmanned Aerial Vehicles (UAVs). In the proposed method, it is assumed that the 3D model of the target infrastructure, the specification of measurement and UAV's features are given. Under those assumptions, the 3D model is regarded as the cluster of vectors and the measuring positions are determined using vector quantization. In this paper, the proposed method is compared with the conventional method by a computer simulation assuming visual inspections.</p>

DOI： 10.1299/jsmermd.2017.1P1-C01

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)  

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)  

Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：The Japan Society of Mechanical Engineers  

<p>The authors aim to realize assistance of complicated body parts as the torso. Securing safety for users is the utmost importance for wearable robots. For safer assistance, it is desirable to directly control the contact state. The contact state is acquired from the pressure distribution sensor on the robot surface, and the robot is controlled to reduce superfluous pressures. In this paper, a novel control method based on predictive is proposed. From current joint angles and pressure distribution of the robot, this method predicts and controls the pressure distribution of the next step. The proposed method is compared with the conventional joint torque control method and the effectiveness of our method is verified.</p>

DOI： 10.1299/jsmermd.2017.1P2-K11

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

<p>Safety control is considered to be the prior requirement for wearable assist robots. In response to the requirement, a control system based on pressure distribution has been researched. However, a robot structure suitable for the control method measured by tactile sensor has not been cleared. In this paper, in order to consider a suitable structure for wearable assist robots with tactile sensor 3D body surface measurement system is presented. The system consists multiple Kinect v2 sensors to measure user's body surface as high densely point cloud data.By fitting some candidate polygons to the data, a suitable polygon will be determined.</p>

DOI： 10.1299/jsmermd.2017.1P2-J07

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical Engineers of Japan  

With an increase in the elderly population, traffic accidents caused by elderly drivers have become an important social issue in Japan. The primary factor of traffic accidents by elderly drivers is a reduction in their driving skill. Therefore, elderly drivers are required by law to conduct regularly a driving aptitude tests in Japan. If the driving skill of the driver is inadequacy, he is subject to punishment, such as driver license revoked. However, there is not appropriate evaluation index of driving skill. We have proposed a modeling method of driving behavior to support one. Proposed driving behavior model is generated based on the actual driving data of driver, and the generated model has some kind of habit and pattern of the driver. Therefore, it is considered that it is possible to evaluate driving skill of driver by analyzing the generated model. According this reason, we aim to propose a modeling method of driving behavior to evaluate driving skill. Here, a coincident timing skill of driver is focused as a driving skill. In the case of driving behavior, the execution timing of driving operations is decided based on the prediction of subsequent change of the outside environment information. The accuracy of this decided execution timing of operation depend on the above prediction is called as the coincident timing skill. In the proposed model, the causality between the situation around a person and operation of driver is modeled by Hidden Markov Model, and timing probability distribution is added to Hidden Markov Model in order to evaluate this coincident timing skill. The timing probability distribution expresses the execution timing of next operation of driver. Therefore, it is possible to detect the information of the coincident timing skill of driver from the timing probability distribution. In the experiment, the controller operation of a radio controlled vehicle is modeled by the proposed method, and the usefulness of the proposed model is examined through some experimental results.

DOI： 10.1541/ieejeiss.137.1353

Scopus

Language：English   Publishing type：Research paper (scientific journal)  

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CiNii Books

Publisher：Electronics and Communications in Japan  

A modeling approach for human action is the focus of this paper. We design a human action model based on the stored data obtained during long-term monitoring of a person. This approach consists of the following two processes. First, several kinds of partial time series data that occur frequently are extracted from the stored data and taken to be human action patterns. Next, the extracted time series data are modeled based on a statistical modeling method such as the hidden Markov model. In this research, we focus on the extraction method for the time series data that occur frequently in the stored data. A person changes his actions according to changes in the situation around him. Moreover, it takes some time for him to perform his action after he recognizes the situation around himself. This time is called the delay time in this paper. A human action model that takes this delay time into consideration leads to greater accuracy in recognition and prediction of human actions based on that action. It is necessary to extract time series data for a situation and an action with the delay time as training data in order to generate the above human action model. In conventional methods, multidimensional time series data are used as the stored data without a distinction between the situation and action data. Also, some partial time series data that occur frequently are extracted from the stored data. Therefore, the delay time is not taken into account. In this paper, we propose a new extraction method for time series data that occur frequently with the time delay taken into consideration. In this method, sets of partial time series data that occur frequently with the delay time are extracted by evaluating the repeatability and similarity between the partial time series data sets with different occurrence frequencies. In the experiment, we extract the interaction motions that occur frequently between two subjects. The utility of the proposed method is examined based on the experimental results.

DOI： 10.1002/ecj.11961

Scopus

Language：English   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)   Publisher：WILEY  

A modeling approach for human action is the focus of this paper. We design a human action model based on the stored data obtained during long-term monitoring of a person. This approach consists of the following two processes. First, several kinds of partial time series data that occur frequently are extracted from the stored data and taken to be human action patterns. Next, the extracted time series data are modeled based on a statistical modeling method such as the hidden Markov model. In this research, we focus on the extraction method for the time series data that occur frequently in the stored data. A person changes his actions according to changes in the situation around him. Moreover, it takes some time for him to perform his action after he recognizes the situation around himself. This time is called the delay time in this paper. A human action model that takes this delay time into consideration leads to greater accuracy in recognition and prediction of human actions based on that action. It is necessary to extract time series data for a situation and an action with the delay time as training data in order to generate the above human action model. In conventional methods, multidimensional time series data are used as the stored data without a distinction between the situation and action data. Also, some partial time series data that occur frequently are extracted from the stored data. Therefore, the delay time is not taken into account. In this paper, we propose a new extraction method for time series data that occur frequently with the time delay taken into consideration. In this method, sets of partial time series data that occur frequently with the delay time are extracted by evaluating the repeatability and similarity between the partial time series data sets with different occurrence frequencies. In the experiment, we extract the interaction motions that occur frequently between two subjects. The utility of the proposed method is examined based on the experimental results.

DOI： 10.1002/ecj.11961

Web of Science

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2023.8

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：徳島大学   Country：Japan  

Event date： 2023.8

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：徳島大学   Country：Japan  

Event date： 2023

Language：English   Presentation type：Oral presentation (general)  

DOI： 10.1109/ONCON60463.2023.10431109

Scopus

Event date： 2023

Language：English   Presentation type：Oral presentation (general)  

Event date： 2023

Language：English   Presentation type：Oral presentation (general)  

DOI： 10.1109/ONCON60463.2023.10430859

Scopus

Event date： 2023

Language：English   Presentation type：Oral presentation (general)  

Event date： 2023