Research On Two-degree-of-freedom PID Control For Permanent Magnet Synchronous Servo System

The permanent magnet synchronous servo system is widely used in the field of industrial motion control,and the change of load moment of inertia often occurs in this field.The change of load moment of inertia may degrade the speed response performance of servo system and cause system instability when seri ous.Aimed at ensuring the good and stable speed response performance of servo system,this paper adopts the control structure PID two degrees of freedom to study the design method of servo system controller.This paper introduces the mathematical model and vector control principle of permanent magnet synchronous motor in synchronous rotating coordinate system,and studies the speed controller on this basis.the speed loop delay is first considered,and according to the characteristics of the two-degree-of-freedom PID control,the PI parameters of the speed controller are designed based on the sensitivity index.compared with the commonly used type i and ii indexes in classical control,the sensitivity index speed controller makes the amplitude margin and phase margin of servo system always maximum before and after the change of moment of inertia,and the robust stability of the system is optimal.In order to improve the following performance of the system,the speed feedforward controller is studied by using the closed-loop transfer function of the system.The addition of the feedforward controller improves the response speed of the servo system under the premise of ensuring the robust stability of the system,and makes the servo system realize dual optimal control.Combined with the closed-loop transfer function of the speed loop simplification model,the advantages of the sensitivity index applied to the speed control of two degrees of freedom are summarized according to the damping ratio and the time domain index.before and after the change of moment of inertia,the sensitivity index speed controller makes the system have a large damping ratio,and the unit step response curves obtained by the closed-loop transfer function have no overshoot and have the opt imal robust stability.A speed two-degree-of-freedom double-closed-loop speed regulation model of permanent magnet synchronous servo system is established on the Matlab/Simulink platform.Finally,this research method is verified on the experimental platfo rm.both simulation and experimental results show that the sensitivity index speed controller makes the system have optimal robust stability.At the same time,with the addition of feedforward controller,the following performance of the system is improved,and the servo system realizes dual optimal control.