Design and integrated stroke sensing of a high-response piezoelectric direct-drive valve enhanced by push-pull compliant mechanisms.

Abstract

Enhancing the dynamic bandwidth of flow control valves based on piezoelectric actuators has attracted much attention in the field of precision fluid control. This paper reports a high-speed piezoelectric direct-drive flow control valve with an enhanced flow rate by introducing a new push-pull complementary compliant mechanism. An improved semi-rhombus compliant amplifying mechanism is designed to amplify the microstroke of piezo-stacks with an enhanced resonance frequency. To facilitate the design, the dynamic stiffness model of the compliant amplifying mechanism is derived and the structural parameters are optimized using the Pareto multi-objective optimization strategy. In addition, a polyvinylidene fluoride (PVDF) based high-response displacement sensor with an improved differential charge amplifier circuit is developed and integrated into the valve to measure the spool displacement in real time. A proof-of-concept prototype is fabricated, and the flow characteristics are experimentally tested in a closed-loop control with the PVDF sensor. The flow rate and dynamic bandwidth of the presented piezo-valve are evidently enhanced, reaching the dynamic bandwidth in excess of 920 Hz (-3 dB) and the flow rate of ±6 l/min (corresponding stroke is 0.2 mm) under the supply pressure of 70 bars.