Electro-pneumatic position tracking control system based on an intelligent phase-change PWM strategy

This paper presents an intelligent phase-change PWM strategy for a position tracking system which includes four solenoid on-off valves and a double-acting double-rod-end cylinder. The proposed technique is designed to minimize the tracking errors and improve the position tracking performance. For an electro-pneumatic system with four valves, only seven switching modes are considered valid. We initially set two switching modes in a pulse width modulation (PWM) period, and this method can also be regarded as a PWM method with changeable phases. In the complete strategy, the operating mode of the system will be selected according to the pressure state and the sliding function. All the switching modes are applied properly in the strategy. A sliding mode controller is designed to utilize the phase-change PWM strategy, and stability of the system is proved. The performance of the proposed strategy is experimentally verified on a field programmable gate array platform. All simulations and experiments verify the effectiveness of the proposed scheme.