Friction compensation control of pneumatic position servo system based on the adjustable stiffness

Abstract

Due to the characteristics of low stiffness, low air source pressure, and easy fluid saturation of the pneumatic servo system, the energy dissipation of the system during the working process is large, the system is easily affected by friction, and the compensation effect is not obvious. Especially, the "Flat roof phenomenon" will become stronger when changing the speed direction. It seriously affects the tracking accuracy of the pneumatic servo system. In this paper, the independent metering valve control structure is proposed to eliminate the energy dissipation caused by the coupling of two chambers, so that the air fluid characteristics are within the linear range as far as possible. The nonlinear adaptive robust control method is designed for the uncertainty of some parameters in the friction, external disturbances, and dynamic loads in the pneumatic system. At the same time, the stiffness adjustment and adaptive robust control of the system are coordinated to improve the dynamic performance of the pneumatic position servo system. The simulation and experimental results show that the adaptive robust controller with stiffness adjustment can effectively reduce the energy dissipation of the system, improve the position tracking accuracy of the system, and weaken the "Flat roof phenomenon" caused by friction.