The Low Speed Control Algorithm Research Of AC Servo System

Nowadays servo control systems are widely used in industry and algricultureproduction, national defense fields, it is of great importance to study their low speedperformance to improve the total control accuracy of high precision numeric controlmachines, radar tracking systems, industry robots and so on. However, the servo motoroften jitters in random when running at a low speed affected by elements such as nonlinearfriction torque, fluctuation torque, interference noise and the precision of photoelectricencode, which deteriorate the entire system greatly. In order to solve this problem, mainfactors influencing the low-speed performance of AC servo system are studied and deepanalysis of the nonlinear friction torque and precision of photoelectric encoder are givenseparately, then mathematical model of AC servo systems and nonlinear friction torque areestablished.Firstly, a sliding mode control algorithm with friction disturbance observer is proposedto eliminate the effect of the nonlinear friction torque. The simulation results show that thismethod can compensate the friction torque effectively and improve tracking precision androbust performance of the low-speed servo system effectively.Secondly, a speed estimator based on position information is proposed to improve themeasurement precision of speed. The speed estimator based on the principle of non-lineardifferential tracker and the simulation results show that it has good dynamic quality andaccurate velocity estimation performance.Finally, algorithms above are transplanted to the actual control system and experimentresults show that the performance of servo system is improved.