Performance evaluation of a miniaturized unconstrained digital on-off switching valve

The technology of pneumatic valves is progressing from large-scale and heavyweight industrial valves to the development of miniaturized valves with less weight. The size and weight of valves are no longer problems due to the development of microelectromechanical system (MEMS) fabrication processes. The limitations of micro valves are their low flow rate and manufacturing complexity. In this paper, we discuss an unusual method of miniaturization using piezoelectric actuated unconstrained valves with comparatively higher flow rate and a simple construction process. Integration of a piezoelectric actuator driver and a microcontroller into the valve unit was accomplished, which allowed reduction of the overall size. Moreover, microcomputer-embedded valves have a digital nature, which enables direct pulse width modulation (PWM) control from the valve. The characteristics of the valve, design parameters, flow tendency and valve response time are discussed. Experimental results of pulse width and pulse frequency modulation are evaluated. The behavior and versatility of unconstrained modulated digital switching valve in control systems are presented in detail, with descriptions of the advantages and disadvantages of unconstrained valve.