Faculty Profiles - DOKI, Shinji

Papers - DOKI, Shinji

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Implementation of Vector Control System On Multi-Core Processor by Using Model-Based Parallelization Tool Reviewed International journal

Kim J., Sagae S., Edahiro M., Honda S., Doki S.

2022 International Power Electronics Conference IPEC Himeji 2022 Ecce Asia page： 1314 - 1319 2022

Authorship：Last author 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

Current Vector Control System Based on a New Discrete dq-Axis IM Model for High Speed Drive Reviewed International journal

Takeuchi T., Doki S.

2022 International Power Electronics Conference IPEC Himeji 2022 Ecce Asia page： 783 - 788 2022

Authorship：Last author Language：English 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

Control Method of Dual Parallel Surface-Mounted Permanent-Magnet Synchronous Motor Systems with Different Parameters Using Single Inverter Reviewed International journal

Park C., Doki S.

2022 IEEE Energy Conversion Congress and Exposition, ECCE 2022 2022

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

Modeling Fabric-Type Actuator Using Point Clouds by Deep Learning Reviewed International journal Open Access

Peng, YH; Yamaguchi, H; Funabora, Y; Doki, S

IEEE ACCESS Vol. 10 page： 94363 - 94375 2022

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

Decoupled Current Vector Control of Dual Three Phase PMSM Drives with Two Independent Micro Control Units Utilizing Current Observer Reviewed International journal Open Access

Wang, S; Doki, S; Suzuki, T; Fujii, K; Hayashi, Y

IEEJ JOURNAL OF INDUSTRY APPLICATIONS Vol. 11 ( 6 ) page： 779 - 789 2022

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

Multisensor robust localization in various environment with correlation checking test Reviewed International journal Open Access

Ohashi N., Funabora Y., Doki S., Doki K.

ROBOMECH Journal Vol. 8 ( 1 ) 2021.12

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

Effects of Inductance Error on Position Sensorless Control of Synchronous Reluctance Motor at Low Speeds Using High-Frequency Current Controller Reviewed International journal

Hayashi T., Kataoka K., Tomita M., Hasegawa M., Doki S.

IEACon 2021 - 2021 IEEE Industrial Electronics and Applications Conference page： 91 - 96 2021.11

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

Capacitor Current Reduction of Double Three Phase PMSM Drive System by Real-time MPC Reviewed International journal

Suzuki A., Doki S., Imai K., Aoki Y., Kondo K.

IECON Proceedings (Industrial Electronics Conference) Vol. 2021-October 2021.10

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

A Novel Decoupling Control of Dual Three Phase Drive with Two Independent Microprocessors Utilizing Current Observer Reviewed International coauthorship

Shen Wang, Kentaro Kitamura, Shinji Doki, Takashi Suzuki

Proceedings of the applied power electronics conference (APEC 2021) 2021.6

Human Action Modeling Method based on the Causality between a Sitution and an Action Reviewed

Kae Doki, Kohjiro Hashimoto, Yuki Funabora, Shinji Doki, Akihiro Torii

IEEJ Transactions on Electronics, Information and Systems Vol. 141 ( 2 ) page： 193 - 204 2021.2

AR video presentation using 3D LiDAR information for operator support in mobile robot teleoperation Reviewed International coauthorship International journal

Doki K., Suzuki K., Torii A., Mototani S., Funabora Y., Doki S.

Sami 2021 IEEE 19th World Symposium on Applied Machine Intelligence and Informatics Proceedings page： 59 - 64 2021.1

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

Fault Tolerant Asymmetrical Six Phase Drive Controlled by Two Microprocessors Reviewed

Shen Wang, Kentaro Kitamura , Shinji Doki, Takashi Suzuki, Norihisa Ito, Yoshitaka Hayashi

Proceedings of The 5th International Electric Vehicle Technology Conference EVTeC 2021 2021

Control Method that Reduces the High Harmonic in the Overmodulation Drive of the Dual Winding Motor during Voltage Supply Unbalance Reviewed International journal Open Access

Suzuki, T; Doki, S

IEEJ JOURNAL OF INDUSTRY APPLICATIONS Vol. 10 ( 6 ) page： 770 - 778 2021

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

AR Image Presentation Based on Sensor Data for Operator Support in Remote Car Driving : -Aiming for Remote Car Driving Reviewed International journal

Doki K., Suzuki K., Yano Y., Funabora Y., Doki S.

2021 IEEE 10th Global Conference on Consumer Electronics Gcce 2021 page： 774 - 776 2021

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

Model Predictive Current Control of PMSM drives for Achieving both Fast Transient Response and Ripple Suppression Reviewed International coauthorship International journal

Kawai Hiroaki, Cordier Julien, Kennel Ralph, Doki Shinji

IECON 2021 - 47TH ANNUAL CONFERENCE OF THE IEEE INDUSTRIAL ELECTRONICS SOCIETY 2021

Maximum Torque Minimum Peak Phase Current of a Dual Winding Interior Permanent Magnet Synchronous Motor Reviewed International journal Open Access

Suzuki, T; Otake, H; Doki, S

IEEJ JOURNAL OF INDUSTRY APPLICATIONS Vol. 10 ( 1 ) page： 11 - 17 2021

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

Control Method that Reduces the High Harmonic in Overmodulation Drive of Dual Winding Motor under Condition of Voltage Supplies Unbalance Reviewed International journal

Suzuki T., Doki S.

23rd International Conference on Electrical Machines and Systems Icems 2020 page： 918 - 923 2020.11

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

The improvement of initial rotor position estimation method with Extended-EMF available at overall speed range by exciting with speed and signal injection Reviewed International journal

Kozakura T., Nimura T., Doki S.

23rd International Conference on Electrical Machines and Systems Icems 2020 page： 252 - 257 2020.11

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

Examination of Magnetization Curve Model for Torque Ripple Reduction of IPMSMs to Compensate for Magnetic Characteristics Reviewed International journal

Akatsuka H., Hasegawa M., Doki S.

23rd International Conference on Electrical Machines and Systems Icems 2020 page： 240 - 245 2020.11

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

Examination of Current Sensor Fail-Safe of PMSM current control system which using current and position state estimation techniques Reviewed International journal

Hori S., Doki S.

23rd International Conference on Electrical Machines and Systems Icems 2020 page： 694 - 698 2020.11

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

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