Faculty Profiles - DOKI, Shinji

Papers - DOKI, Shinji

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Funabot-Sleeve: A Wearable Device Employing McKibben Artificial Muscles for Haptic Sensation in the Forearm Reviewed International journal

Yanhong Peng, Yusuke Sakai, Yuki Funabora, Kenta Yokoe, Tadayoshi Aoyama, Shinji Doki

IEEE Robotics and Automation Letters Vol. 10 ( 2 ) page： 1944 - 1951 2025.2

Preliminary Study on Task Division for UAV-Based Visual Inspection of Large Structures with Multiple Flights Using 3D Urban Models Reviewed International journal

Haneda M., Funabora Y., Doki S.

2025 IEEE/SICE International Symposium on System Integration, SII 2025 page： 1381 - 1386 2025

Authorship：Last author Language：English Publishing type：Research paper (international conference proceedings) Publisher：2025 IEEE/SICE International Symposium on System Integration, SII 2025

This paper addresses the problem of task division based on 3D urban models for visual inspection using a UAV with multiple flights. When inspecting large structures for damage detection, UAVs are often flown multiple times to obtain high-resolution data from all areas. Research is progressing on coverage path planning (CPP) methods for data collection in a single flight, and the 3D models of the target required for this can be readily obtained. However, the automation of task division for each flight has not been extensively studied. Because the scale of the target is large, it is necessary to execute a task division method that optimizes the performance efficiency of UAVs within a practical calculation time. This paper presents a task division method for data collection by multiple flights of a UAV based on the decomposition of the 3D urban models. Forming a framework in which data collection tasks are divided based on the 3D mesh decomposition, and then the CPP method is applied to each task, this enables efficient inspection of large-scale structures. In this paper, we implement three basic methods based on the strategies of avoiding going far, equalizing the amount of each task, and reducing unnecessary movement as preliminary research. Each method applies to objects on a scale of several hundred meters, and evaluates their performance in automated data collection.

DOI： 10.1109/SII59315.2025.10870973

Viewpoint Generation Algorithm for Gimbal-Mounted Robots for Visual Inspection of Civil Engineering Structures Reviewed International journal Open Access

Haneda M., Wu W., Funabora Y., Doki S., Doki K.

IEEE Access 2025

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

We propose a viewpoint generation algorithm for the visual inspection of civil engineering structures using robots equipped with a gimbal-mounted camera. This algorithm enables robots to completely inspect target surfaces at the required spatial resolution while reducing movement by effectively utilizing the gimbal. Previous studies generally assume that the camera is always oriented orthogonally to the target surface, and they focus on the inspection position optimization problem, resulting in the underutilization of gimbals and heavy movement of robots. In this study, firstly we have formulated the conditions under which the collected data’s quality does not deteriorate in terms of damage detection, and we have relaxed the orthogonal measuring restrictions. Based on the conditions, we propose a viewpoint generation algorithm that can carry out inspection work by changing measurement orientations instead of moving the robot. In simulation experiments, our method reduces inspection time by 47.7% compared to the benchmark method for the same tasks of inspecting a pier surface with the required spatial resolution. In addition, the viewpoint generation time was reduced by 96.8% compared to the benchmark method. We also conducted experiments in real environments using pan-tilt heads and confirmed that our algorithm can collect data qualified for the damage detection of visual inspections.

DOI： 10.1109/ACCESS.2025.3546992

Feasibility of loop-gain tuning for general measurement systems inspired by quantum locking for DECIGO Reviewed International journal

Ishikawa, T; Kawasaki, Y; Tsuji, K; Shimizu, R; Umemura, K; Wu, B; Iwaguchi, S; Michimura, Y; Nagano, K; Enomoto, Y; Komori, K; Doki, S; Furusawa, A; Kawamura, S

CLASSICAL AND QUANTUM GRAVITY Vol. 41 ( 21 ) 2024.11

Language：English Publishing type：Research paper (scientific journal) Publisher：Classical and Quantum Gravity

A series of quantum locking theories have been proposed to enhance the quantum-noise-limited target sensitivity of the DECi-hertz Interferometer Gravitational wave Observatory. The quantum locking that uses a square completion optimizes the sensitivity across all frequencies. However, a substantial amount of data-series must be post-processed since the square completion is a form of signal processing technique. This paper approaches the optimal sensitivity across all frequencies from an alternative perspective: by optimizing the frequency dependence of a servo gain in a feedback loop. The optimal servo gain is formulated by comparing the alternative method with the square completion method for the same optical setup. This will be shown in general noise issues extending the framework of the quantum locking. We find that the optimal servo gain forms a non-feasible filter but has certain characteristics. We also find that the noise of the measurement signal deteriorates proportionally to the noise measured in the feedback loop when the servo gain is slightly imperfect.

DOI： 10.1088/1361-6382/ad7cb6

Gravity Compensation Method for Whole Body-Mounted Robot With Contact Force Distribution Sensor Reviewed International journal

Masaoka, S; Funabora, Y; Doki, S

IEEE ROBOTICS AND AUTOMATION LETTERS Vol. 9 ( 9 ) page： 7843 - 7850 2024.9

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

The emergence of sheet-type force distribution sensors has allowed direct measurement of contact force. We developed a wearable assistive robot that can directly measure contact force and investigated the gravity compensation effect of contact-force-based control. For conventional robots that do not measure the force acting between the robot and the human body (contact force) directly, a precise robot model is required for gravity compensation, which is difficult to implement in software. In the first experiment, we examined a method of gravity compensation using only joint sensors in torque-based control, which is a common conventional method, and assessed the difficulty of this method. In the next experiment, which involved one healthy subject, we confirmed that contact-force-based control has a significant gravity compensation effect without requiring a rigorous robot model. Experiments with two additional healthy subjects using the same parameters revealed that even rough parameter tuning can produce a gravity compensation effect. This letter not only proposes a simplified gravity compensator for wearable assistive robots but also demonstrates the robustness of parameter tuning in contact-force-based control under static conditions. Based on the findings of this letter, we will further study the possibility of other kinds of disturbance compensation and dynamic conditions in the future.

DOI： 10.1109/LRA.2024.3433308

Funabot-Finger Cot: Bio-Inspired Worm Robot for Peristaltic Wave Locomotion and Tubular Structure Climbing Reviewed International journal

Sato Y., Peng Y., Funabora Y., Doki S.

2024 IEEE/SICE International Symposium on System Integration, SII 2024 page： 1387 - 1392 2024

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

Evaluation and Enhancement of Resolution-Aware Coverage Path Planning Method for Surface Inspection Using Unmanned Aerial Vehicles Reviewed International journal

Wu, WT; Funabora, Y; Doki, S; Doki, K; Yoshikawa, S; Mitsuda, T; Xiang, JY

IEEE ACCESS Vol. 12 page： 16753 - 16766 2024

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

Pole Change Method Without Torque Fluctuation in Multiphase IM Drive System Reviewed International journal

Kobayashi M., Doki S., Nikaido R., Chiba A., Kobayashi M.

ECCE Europe 2024 - Energy Conversion Congress and Expo Europe, Proceedings 2024

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

Expansion of Field-Oriented Control Operation Range of Dual Three-Phase Synchronous Motor with Flux Weakening Control in the Inverter Overmodulation Region Reviewed International journal

Hao R., Doki S.

ECCE Europe 2024 - Energy Conversion Congress and Expo Europe, Proceedings 2024

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

Applications of Augmented Reality in Assisting Structure Surface Data Collection Using Unmanned Aerial Vehicles Reviewed International journal Open Access

Wu, WT; Hong, YH; Funabora, Y; Doki, S; Doki, K

IEEE ACCESS Vol. 12 page： 143106 - 143117 2024

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

Verification of Mehcanism How Fabric Actuator Evoke Pinched Tactile by Using Force Distribution Sensor Reviewed International journal

Masaoka S., Sato Y., Funabora Y., Doki S.

Proceedings of the 2024 IEEE International Conference on Cyborg and Bionic Systems, CBS 2024 page： 263 - 266 2024

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

Verification of Compliance on Funabot-Plate: Semisoft Assistive Robot with Artificial Muscle and Rigid Plate Reviewed International journal

Masaoka S., Yasuda R., Funabora Y., Doki S.

2024 18th International Conference on Control, Automation, Robotics and Vision, ICARCV 2024 page： 441 - 446 2024

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

The Impact of Equipment Specifications on the Efficiency of Visual Inspection using Unmanned Aerial Vehicles Reviewed International journal

Wu W., Funabora Y., Doki S., Doki K.

10th 2024 International Conference on Control, Decision and Information Technologies, CoDIT 2024 page： 1505 - 1510 2024

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

Smooth Pole Change Method for Multiphase Induction Motor Drive System Reviewed International journal

Kobayashi M., Doki S., Kato H., Itoh J.I., Kobayashi M.

2024 IEEE International Conference on Electrical Systems for Aircraft, Railway, Ship Propulsion and Road Vehicles and International Transportation Electrification Conference, ESARS-ITEC 2024 2024

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

Investigation of Sensory Provision for Calf and Shin Using Fabric Actuator Reviewed International journal

Masaoka S., Fukatsu H., Funabora Y., Doki S.

Proceedings of the 2024 IEEE International Conference on Cyborg and Bionic Systems, CBS 2024 page： 259 - 262 2024

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

An Innovative Discrete-Time dq-Axis Model Considering Phase Discretization Error for High-Speed IM Drive and Its Analysis Reviewed International journal

Fang Z., Doki S.

2024 IEEE International Conference on Electrical Systems for Aircraft, Railway, Ship Propulsion and Road Vehicles and International Transportation Electrification Conference, ESARS-ITEC 2024 2024

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

Funabot-Suit: A bio-inspired and McKibben muscle-actuated suit for natural kinesthetic perception Reviewed International journal

Yanhong Peng, Yusuke Sakai, Koki Nakagawa, Yuki Funabora, Tadayoshi Aoyama, Kenta Yokoe, Shinji Doki

Biomimetic Intelligence and Robotics Vol. 3 ( 4 ) page： 100127 - 100127 2023.12

Model predictive current control with a finite set of novel voltages and modulator in permanent magnet synchronous motor drives Reviewed International coauthorship International journal

Kawai, H; Cordier, J; Kennel, R; Doki, S

IET ELECTRIC POWER APPLICATIONS Vol. 17 ( 9 ) page： 1197 - 1211 2023.9

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

Direct Speed Control Based on Finite Control Set Model Predictive Control With Voltage Smoother Reviewed International coauthorship International journal

Kawai, H; Zhang, ZB; Kennel, R; Doki, S

IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS Vol. 70 ( 3 ) page： 2363 - 2372 2023.3

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

A Novel Decoupling Control Scheme for Non-Salient Multi-Three-Phase Synchronous Machines Based on Multi-Stator Model Reviewed International journal Open Access

Wang, S; Imai, K; Doki, S

IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS Vol. 59 ( 1 ) page： 886 - 896 2023.1

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

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