Research on position control of pneumatic switch valves system based on PWM

The pneumatic system based on switch valves has many advantages, such as low cost, high performance, easy maintenance, and so on. The pressure fluctuation produced by open and close of the switch valve will impact on the accuracy of pneumatic position system. A new pneumatic system is established containing an asymmetric cylinder and four switch valves. The Pulse-Width Modulation (PWM) is used to control the system. Every two valves work together, the work time of valves in each PWM period is adjusted by controlling the duty cycle to control the position of the cylinder's piston. The steady-state duty cycle is defined to improve the stability of the system when the position deviation is zero or less than the error range. The pressure fluctuation is simulated under different duty cycle and frequency, and the steady-state duty cycles are 47.5% and 52.5%. The model of the system is founded with AMESim, and the simulation results show that the stable time is less than 5 seconds, positional error is less than 5%, accordance with the results of experiments.