PRECISE CONTROL OF THE PISTON POSITION AND THE PRESSURE OF CYLINDER CHAMBERS FOR THE PNEUMATIC ACTUATOR

摘要

This paper presents a proportional-derivative controller (PD controller) for a pneumatic actuator, by using the gas internal energy of the cylinder's two chambers as the set point of the PD controller. The proposed control scheme is essential to overcome the influence of the gas compressibility and pneumatic system's inherent strong non-line feature, and control the piston position and the chamber pressure simultaneously. A pneumatic position servo model is developed by Simulink tools in the form of system function (S-function). The maximum steady-state error of 0.19 mm for the piston position and 0.001 MPa for the chamber pressure have been verified in simulations. The test rig of the vertical hopping is constructed, and the experimental results of the pneumatic position servo control on the pneumatic actuator show that the chamber pressure error is less than 0.002 MPa, the piston positioning error is less than 0.31 mm and there is no overshooting. The experimental results also show that the established mathematical model and the simulation results are correct. Consequently, the practical experiments of vertical hopping are successful, which validates the proposed method further.