Active Disturbance Rejection Control of Servo Systems with Friction

Friction exists in all motions, and friction is the key factor that influences the low velocity performance of servo systems. It usually caused the steady-state error of servo systems and resulted in the creeping phenomenon in low velocity motions. Friction is complicated nonlinear process with time-varying uncertainties. The traditional PID controller of servo systems with fricition was not satisfactory in control precision. The algorithms and principles of a new ADRC (active disturbance rejection controller) were analyzed in the paper. Then the ADRC of the high precision servo system was designed. Moreover the effects of estimating and compensating the friction force in the ADRC servo system were studied through simulation tests using Matlab and Simulink in the paper. The results of simulation tests showed that ADRC algorithms had higher position tracking precision. It could eliminate the oscillation and steady-state error of the servo system completely.