Research On Control Method Of Low-speed And High-torque Permanent Magnet Synchronous Motor

Permanent magnet synchronous motor has the advantages of small torque ripple,high operating efficiency,simple structure,small size,etc.,so the direct drive system of permanent magnet synchronous motor had become a hot spot in the current research.But the direct drive system has the speed and torque wave problems caused by motor parameter perturbation and load during operation,which in turn leads to rigid fatigue and increased electrical energy output on the motor shaft.Therefore,this paper studies the control method of low-speed and high-torque permanent magnet synchronous motor,which aims to suppress speed and torque fluctuations and improve the running performance of the motor.Aiming at the problems of parameter perturbation caused by non-ideal factors of motor and control system.This paper studies the sliding mode control strategy that is not affected by parameter perturbation and external disturbance.In order to solve the problems of severe chattering due to the excessive switching gain of the state variable in the sliding stage,this paper designs a speed control strategy for low-speed large-torque permanent magnet synchronous motor based on the compound variable exponential reaching law.The variable exponential term and the weighted integral term in the compound variable exponential reaching law had different weights in the control to take into account the fast start-up speed and static performance of the motor.In order to further optimize the dynamic performance of the permanent magnet synchronous motor speed regulation system,the selection of the fast item k value in the compound variable exponential reaching law control strategy will lead to the problem of the system approach speed and chattering vibration contradictory.In this paper,a sliding mode control strategy based on the reachching law of the power exponential is proposed.The proximity law adaptively change the fast term parameters in the approach law according to the process by which the state variables move away from and approach the sliding die surface.The integral slip surface is designed,so that the state variable is located on the slip surface from the beginning.The power-varying exponential reaching law strategy is used to further improve the smoothness of speed switching and the dynamic performance of rotational speed under burst load.In view of the problem that the load side disturbance will be transmitted directly to the motor shaft head,causing electromagnetic torque fluctuations,the sliding mode load observer is designed.A traditional sliding mode load observer is established,and a sliding mode load disturbance observer is constructed based on the mathematical model of this observer combined with a non-singular terminal sliding mode.The observer can increase the system convergence speed,compensate for random disturbances,reduce the fluctuation of electromagnetic torque,and increase the robustness of the system.