Faculty Profiles - DOKI, Shinji

Papers - DOKI, Shinji

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Improvement in control performance of PMSMs by deactivation of antiwindup control in the overmodulation range of an inverter Reviewed International journal

Nakayama Y., Doki S.

2018 20th European Conference on Power Electronics and Applications, EPE 2018 ECCE Europe 2018.10

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.

Investigating Pole Assignment of Full-Order Observer Based on Extended Electromotive Force for Position Sensorless Control of IPMSMs Reviewed International journal

Toshiya Mabuchi, Takato Hatanaka, Mutuwo Tomita, Masaru Hasegawa, Shinji Doki, Shinji Kato

Proceedings - 2018 23rd International Conference on Electrical Machines, ICEM 2018 page： 1579 - 1585 2018.10

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

Maximum Torque Control Reference Frame Based on a Torque Map for IPMSMs with Large Inductance Variation Reviewed International journal

Ohta K., Ohnuma T., Doki S.

2018 International Power Electronics Conference, IPEC-Niigata - ECCE Asia 2018 page： 1223 - 1227 2018.10

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

The Multiple Degree of Freedom based Neutral Point Potential Control of Three Level Neutral Point Clamped Converters Reviewed International journal

Guan B., Doki S.

2018 International Power Electronics Conference, IPEC-Niigata - ECCE Asia 2018 page： 1032 - 1037 2018.10

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

High Stability V/f Control of PMSM Using State Feedback Control Based on n-t Coordinate System Reviewed International journal

Matsuki Y., Doki S.

2018 International Power Electronics Conference, IPEC-Niigata - ECCE Asia 2018 page： 2224 - 2228 2018.10

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

New Search Algorithm of Model Predictive Control to Reducing Calculation Amount for Improving Steady Current Control Performance Reviewed International journal

Shimaoka M., Doki S.

2018 International Power Electronics Conference, IPEC-Niigata - ECCE Asia 2018 page： 1747 - 1751 2018.10

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

PMSM Model Discretization in Consideration of Park Transformation for Current Control System Reviewed International journal

Inoue M., Doki S.

2018 International Power Electronics Conference, IPEC-Niigata - ECCE Asia 2018 page： 1228 - 1233 2018.10

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

Majority rule sensor fusion system with particle filter for robust robot localization Reviewed International journal

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

IEEE/ASME International Conference on Advanced Intelligent Mechatronics, AIM Vol. 2018-July page： 1106 - 1111 2018.8

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

Study on an Evaluation Method of Coincident Timing Skill of Driver Based on Driving Behavior Model of Brake Operation Reviewed International journal

Hashimoto K., Doki K., Doki S.

IEEE International Symposium on Industrial Electronics Vol. 2018-June page： 782 - 787 2018.8

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

The Voltage Phase Control Strategy for Six-Step Operation in SPMSM Drives Considering the 6/12-Order Torque Ripple Reviewed International journal

Guan B., Doki S.

ITEC Asia-Pacific 2018 - 2018 IEEE Transportation Electrification Conference and Expo, Asia-Pacific: E-Mobility: A Journey from Now and Beyond 2018.8

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

A neutral point potential control for three-level neutral-point-clamped converters based on the search optimization method of the two degrees of freedom Reviewed International journal

Bo Guan, Shinji Doki

IEEJ Transactions on Electrical and Electronic Engineering Vol. 13 ( 8 ) page： 1196 - 1207 2018.8

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

A robust neutral point potential control for single phase three level rectifier based on the multiple degree of freedom Reviewed

Guan B.

Proceedings of the IEEE International Conference on Industrial Technology Vol. 2018-February page： 606 - 611 2018.4

Filter setting for improving the current control performance of IPMSMs in overmodulation region of inverter Reviewed

Yosuke Nakayama, Shinji Doki, Atsushi Matsumoto, Masaru Hasegawa

Proceedings of the International Conference on Power Electronics and Drive Systems Vol. 2017- page： 703 - 708 2018.2

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

Mathmatical models on extended electromotive force exited by high frequency signal injection and its robustness for position estimation of PMSM Reviewed International journal

Shota Kondo, Shinji Doki, Mutuwo Tomita

Proceedings of the International Conference on Power Electronics and Drive Systems Vol. 2017- page： 172 - 177 2018.2

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

Contact force distribution predictive control system for wearable robot with tactile sensors Reviewed International journal

Sato A., Funabora Y., Doki S., Doki K.

2017 Asian Control Conference, ASCC 2017 Vol. 2018-January page： 1373 - 1378 2018.2

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

Study on the Model Structure of Human Machine Operation to Evaluate a Coincident Timing Skill Reviewed

Kohjiro Hashimoto, Kae Doki, Shinji Doki

Electronics and Communications in Japan Vol. 101 ( 2 ) page： 74 - 86 2018.2

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

Position sensorless control for wound-field synchoronous motor with double three-phase wound stator using new EEMF model Reviewed International journal

Imai K., Doki S., Fujii K., Jung S.

31st International Electric Vehicle Symposium and Exhibition, EVS 2018 and International Electric Vehicle Technology Conference 2018, EVTeC 2018 2018

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.

Improvement of position control error for position sensorless control based on pattern matching method Reviewed

Song H., Doki S.

IEEJ Transactions on Industry Applications Vol. 138 ( 12 ) page： 902 - 910 2018

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

High response torque control of IPMSM using state feedback control based on n-t coodinate system Reviewed International journal

Matsuki Y., Doki S.

IEEJ Transactions on Industry Applications Vol. 138 ( 7 ) page： 563 - 573 2018

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

Evaluation method to estimate position control error in position sensorless control based on pattern matching method Reviewed International journal

Hamin Song, Shinji Doki

IEEJ Journal of Industry Applications Vol. 7 ( 1 ) page： 73 - 79 2018

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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