Study On The Steady Control Of Permanent Magnet Synchronous Motor At Low-speed

The permanent magnet synchronous motor(PMSM)has simple structure,high efficiency,high torque-inertia ratio and good low-speed tracking performance.It is widely used in high precision servo control applications such as high precision CNC machine tools,telescope control systems and radar satellites.In recent years,with the improvement of target detection requirements and manufacturing technology,the telescope diameter manufactured by the telescope control system keeps increasing.Large direct-driven telescopes at home and abroad have adopted the permanent magnet synchronous motor servo control system to replace the original dc servo control system to improve the low-speed tracking performance of the telescope.This dissertation mainly studies the stability of the low-speed control of PMSM,with the purpose of broadening the application of PMSM in the high-precision servo control system,especially the telescope control system.The main factors that affect the stability of the motor at low speed are the torque ripple of the motor and the speed detection error in the control system.In this dissertation,the stability of the motor at low speed is improved from the two aspects of suppressing the torque ripple and instantaneous detection of the speed.First of all,in order to carry out the research of speed pulsation suppression and speed detection algorithm in the following dissertation,this dissertation briefly introduces the mathematical model of PMSM under three coordinate systems(three-phase stationary coordinate system,two-phase stationary coordinate system and synchronous rotating coordinate system),reveals the relationship between speed pulsation and torque pulsation,describes the basic principle and frame structure of the id=0 vector control system of PMSM,further analyzes the influencing factors of speed ripple,and summarizes its influencing laws.Secondly,aiming at suppressing the speed ripple of PMSM,an ADRC compound controller with current injection is designed in this dissertation,which is compared with the conventional PI controller and PI superposition current injection controller.A speed loop active disturbance rejection control(ADRC)is designed to suppress the external load disturbance of the motor and a current compensation module is designed to suppress the motor torque ripple,then the ADRC and the current compensation module are combined to obtain an ADRC compound controller with current injection.The simulation results show that the proposed method is more effective in suppressing the system speed ripple at low speed,and can guarantee the system's good dynamic response performance and robustness in the case of external load disturbance.Furthermore,considering that the average speed measurement algorithm is difficult to meet the speed measurement accuracy at low speed and cannot eliminate the speed measurement delay,an adaptive Kalman observer is designed in this dissertation.The third-order Kalman observer is designed according to the mechanical motion equation of the motor,the design principle of the parameter matrix is obtained,and an adaptive mechanism is introduced to eliminate the speed measurement delay when the load changes suddenly.The simulation results show that compared with the average velocity measurement and the Kalman observer method,the proposed method can effectively reduce the speed measurement delay and improve the speed measurement accuracy when the motor is running at low speed.Finally,in order to verify the low-speed stable control algorithm proposed in this dissertation,the low-speed control experiment was carried out based on the PMSM platform in the laboratory.The experimental results verify that the proposed algorithm has good low-speed running stability.