Friction Estimation and Compensation of Pneumatic Force Servo System

Friction exists in every mechanical system, and exerts bad influences on its operation performance, which will cause cylinder crawling phenomenon when it runs under low speed. In this paper, the analysis of the cylinder crawling phenomenon is proposed, as friction is complicated and impossible to measure its exact value, the estimation of friction by using extended Kalman filter (EKF) is introduced, then the estimated friction is added to the control input for friction compensation. The studies show that the pnuematic force servo system with friction estimation and compensation by using EKF has better performance than the system without friction compensation, for instance it has better dynamic and statistic characteristics, higher tracking accuracy, higher robustness, and the response time is also more quickly.