Research On Permanent Magnet Synchronous Motor Position Control System With Disturbance Observer

With the continuous development of power electronics, motor manufacturingtechnology and digital control technology, the scope of application of the AC controlsystem is more extensive. But in some applications, for example the process ofpicking up and unloading clog for machine arm, position control system can beeffected by the outside load disturbance, and the performance of control systemdeclines. This paper uses the disturbance observer to restain the load disturbance.The typical three-loop control system, including current loop, speed loop andposition loop, is used in the PMSM position controlsystem, but the anti-disturbanceability is poor. In consideration of system responses to the external disturbance, thedisturbance observer (DOB) is proposed to improve the robustness of positiontracking. After the principle of DOB is analyzed, the whole control model ofposition control system with three-loop PID controller and DOB is designed. Basedon the mathematical model and parameters of PMSM, the calculation method ofthree-loop PID controller parameters is analyzed. On this basis, the nominal modelof DOB is deduced, and the low-pass filter is mainly analyzed.Based on the control strategy of PMSM position controlsystem and themathematical model deduced, the entire control system is built by theMATLAB\SIMULINK software. This software provides a wealth of simulationmodels, including the three-phase bridge circuit model and the PMSM model. TheSVPWM generation module, DOB module and the PI controller module are built onthe base of the model paramenters derived，and the simulation analysis is conductedfinally. Results of the simulation validates that position can not only follow thegiven position on request, but anti-disturbance ability of position controlsystem getsimproved obviously after introducing the DOB.The hardware platform for PMSM position control system is established in thispaper. The control circuit uses TMS320F28027chip, which has the advantage ofsmall size, strong function and low cost. To improve the accuracy of the currentsampling, external current sampling and high accuracy AD converter circuit aredesigned. Finally, specific experiment is done, and the speed-loop, the position-loopof control system and impact on the location by load disturbance are tested. Theresults of experiment show that the speed and position can follow a given signal in atimely manner, and the robustness of position control system is significantlyimproved after the DOB is introduced.