Flow Rate Ripple Suppression Based on Phase Shift Optimization of Two PWM-Actuated High-Speed Valves

Pulse Width Modulation (PWM) actuated high-speed valves offer a cost-effective alternative for pneumatic systems due to their fast switching abilities and also the simplicity of their control. Tuning the duty cycle results in almost proportional flow rate output. However, the large flow rate ripple due to the air pulses, makes these valves unsuitable for flow control applications. This paper introduces a solution to suppress this ripple by adding a second valve with a 180 ◦ phase shift. The experimental analysis demonstrates a flow rate ripple reduction of 96.5% in the worst-case scenario, which is at 0.5 duty cycle, and 0.4 MPa. Through extensive testing of combinations of duty cycle and phase shifts at several pressure difference levels, the optimal phase shift at all combinations is found to be 180 ◦ . These results provide a promising solution to implement PWM-actuated high-speed valves for flow control applications.