Dr. Liwei Zhang Profile

Dr. Liwei Zhang

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Proceedings Article | 10 August 2023 Paper

A control method for a larger speed range of permanent magnet synchronous motor controlled without speed sensor

Dacheng Ren, Liwei Zhang

Proceedings Volume 12748, 127484T (2023) https://doi.org/10.1117/12.2689661

KEYWORDS: Switching, Control systems, Sensors, Mathematical modeling, Switches, Resistance

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Permanent magnet synchronous motor has the advantages of simple structure, high power density, high power factor and large starting torque, which is widely used in various occasions. However, high performance permanent magnet synchronous motor control methods need to obtain accurate motor rotor speed and position information. However, high precision sensors are costly and prone to failure. Therefore, the speed sensorless control algorithm of permanent magnet synchronous motor is a hot topic for scholars. The existing speed sensorless control strategies are mainly observer methods based on the motor back EMF and algorithms based on the irrational characteristics of the motor. However, the observer method based on the motor back EMF is only suitable for the middle and high speed conditions of the motor. Although the algorithm based on the irrational characteristics of the motor can adapt to the low speed condition of the motor, it needs to continuously give additional excitation to the motor, the voltage utilization rate of the inverter is reduced, and the dynamic performance is not perfect. In this paper, the highfrequency injection method based on the irrational characteristics of the motor is used in the low speed condition, and the observer method based on the motor back electromotive force is used in the high speed condition, and the switching strategy is optimized to realize the speed sensorless control of the permanent magnet synchronous motor in a wider speed range. The simulation results show that, The composite control strategy adopted in this paper can accurately obtain the motor speed and rotor position information in a wider speed range, and the system runs well when the algorithm is switched.

Proceedings Article | 1 August 2022 Paper

Simulation research on auxiliary power supply system of medium and low speed maglev train

Liwei Zhang, Yueqi Chen, Jiawei Yang, Lu Shen

Proceedings Volume 12257, 1225727 (2022) https://doi.org/10.1117/12.2640306

KEYWORDS: Power supplies, Control systems, Logic, Fuzzy logic, Systems modeling

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Auxiliary power supply system is an important part of medium and low speed maglev train. It is mainly composed of auxiliary inverter, charger, suspension power supply, several battery packs and several loads. Taking Qingyuan medium and low speed maglev train as an example, the actual topology of its auxiliary power supply system is analyzed, the models of auxiliary inverter, charger and suspension power supply are established in the simulation system, and the internal working principle and working process of the system are studied in detail. The auxiliary inverter adopts three loop control and SVPWM control mode of current and voltage double closed loop, which improves the stability of the auxiliary inverter during load switching. Combined with the charging characteristic curve of battery pack, the constant current and constant voltage charging control strategy is studied, and the control logic of the simulation system is designed according to the actual operation of the auxiliary power supply system. The system level simulation on MATLAB®/Simulink® platform shows that each component can work stably under rated parameters, and meet the design requirements and the working requirements of auxiliary power supply system. Finally, its rationality and stability are analyzed. The robustness of the auxiliary power supply system model is verified by simulation. This research provides a certain theoretical basis for the research of auxiliary power supply system of medium and low-speed maglev train.

Proceedings Article | 1 August 2022 Paper

Yaw stability control for modern trackless train based on feedforward-feedback control system

LiWei Zhang, JinQi Liu, MengLei Zhang, ZhongChao Song

Proceedings Volume 12257, 122573U (2022) https://doi.org/10.1117/12.2640327

KEYWORDS: Motion models, Control systems, MATLAB, Detection and tracking algorithms, Curium, Mathematical modeling, Instrument modeling, Vehicle control, Feedback control, Algorithm development

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In order to improve the yaw motion stability of the rear compartment of modern trackless train connected by six articulated devices, a yaw rate feedforward-feedback control strategy is proposed. First, the feedforward desired yaw rate is calculated based on the 3 degree-of-freedom linear reference model, which includes the first two compartments of the vehicle. Second, the problem of calculating compensate yaw rate is solved by sliding mode algorithm, and the target yaw rate is obtained by adding the feedforward desired yaw rate to the compensated yaw rate. At last, the PI control algorithm is used to calculate the yaw moment which is distributed to the wheel by the torque distribution algorithm. U-turn and S-turn cases are designed to verify the performance of the control strategy. Simulation results show that the proposed feedforwardfeedback controller has less yaw rate tracking error compared with the uncontrolled one, and the path-following error is less than 0.12m. The yaw motion stability of the vehicle is guaranteed.

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