Disturbance Observer Based Control For Permanent Magnet Synchronous Motor Speed-regulation System

In recent decades,with the development of modern power electronics and motor control technology,the motor control system has been widely used in electric vehicles,robotics,CNC machine tools and etc.Because of its high efficiency,wide speed range and rapid response capability.Permanent magnet synchronous motor plays an important role in the speed control system.However,the permanent magnet synchronous motor and its inverter drive system is a nonlinear multivariable system,the classic control theory can not achieve a good control effect.More and more scholars and experts begin to study the modern control theory for permanent magnet synchronous motor.The paper first introduces the mathematical model of permanent magnet synchronous motor.Based on the mathematical model,it discusses synchronous motor speed control system using a structure of double closed loops(outer speed loop and inner current loop).Then it introduces the current loop control scheme,based on the transfer function.We can get a second-order system through the pole-zero cancellation,and select the appropriate damping ratio and bandwidth to obtain a desired system response.Then it introduces a speed loop control method based on PI controller and IP controller.Theoretical analysis shows that with the same tracking performance,the disturbance rejection ability of the PI controller is the same with the IP controller,the rising time of the PI controller is less than that of the IP controller,but the overshoot of it is more than that of the IP controller.Finally,it verifies the effectiveness by MATLAB simulation and provides a reference for the controller selection of PMSM.For a better control performance,the paper introduces the disturbance observer to PMSM control system.Then it designs a P+DOB controller for the speed loop.Theoretical analysis shows that the P+DOB controller is actually a two degree of freedom controller.We can adjust the scale factor and the low-pass filter bandwidth to regulate the tracking performance and disturbance rejection ability separately.Then it compares the P+DOB controller with first-order low-pass filter and the P+DOB controller with second-order low-pass filter.When they have approaching tracking performances and disturbance rejection abilities,the P+DOB controller with second-order low-pass filter has less current and speed fluctuations.Finally,it verifies the effectiveness by MATLAB simulation.