Sliding mode control with friction observer and load observer of PMSM

Aiming at the problems of friction and the load torque disturbance in the servo system, the Dahl friction model and the LuGre friction commonly used in servo system were analyzed and compared to discuss a modified Dahl model which could describe the phenomenon of friction well. Then based on the method of the Lyapunov stability analysis, an algorithm of friction compensation with modified Dahl model was designed, which was used to control the current loop. To observe the changes of load torque, load torque observer was designed, the result of the observation was feedback to the speed control loop and the speed loop was controlled by sliding mode control method (SMC). The results of simulation and experiment indicate that the precision of the system and the effects of load mutation rate have been improved.