Multicontroller Positioning Strategy for a Pneumatic Servo System Via Pressure Feedback

A backstepping-based controller is designed to improve positioning speed of a pneumatic servo system by pressure feedback. A least-square method is used to identify parameters for obtaining a relatively accurate proportional valve model. In addition, an extended state observer is designed to estimate total nonlinearities caused by friction and unmodeled dynamics. A backstepping-based controller is proposed to increase convergence speed, and another nonlinear error feedback controller is used to keep positioning accuracy. That is, a multicontroller strategy containing the two controllers is introduced to improve performance of the pneumatic servo system. Finally, experimental results with response time 0.5 s and accuracy 0.05 mm indicate the capabilities of the proposed method.