Abstract: In order to overcome steady-state error and low-speed creeping problems caused by friction in pneumatic proportional systems, nonlinear friction force compensation method is adopted. A Friction model of the pneumatic proportional system is constructed on the basis of viscoelastic theory and Stribeck model. Incorporating the friction model in dynamical model of valve-controlled cylinder system constructs a complete system motion model. The high-frequency low-amplitude chatter signal is introduced into the system to analyze its influence on the system friction mechanism and stability. The results show that a part of static friction is turned into dynamic friction, the maximum static friction is reduced and the response speed is raised. Consequently, the stick-slip motion is transformed into a steady one by adding proper chatter signal. The experimental results show that the positioning precision is improved from 0.516 mm to 0.284 mm, and the hysteresis time is shorten from 0.17 s to 0.02 s when the chatter frequency is 3.3times of the natural one. The results prove that the friction chatter-compensation theory proposed for the pneumatic proportional system is correct.

Key words: Chatter signal, Compensation, Friction force, Stribeck model