Dynamic Design of a Novel High-Speed Piezoelectric Flow Control Valve Based on Compliant Mechanism

Piezoelectric actuators are particularly interesting in high-speed precision flow control valves due to their fast dynamic response and simple structure. However, concurrently improving the dynamic bandwidth and flow rate has been a challenging issue. In this article, a novel two-stage flow control valve driven by amplified piezoelectric actuator is proposed, fabricated, and tested with the step response time of 5 ms, flow rate of 70 L/min, and the dynamic bandwidth of 155 Hz at the supply pressure of 30 bar. An improved rhombus-type compliant mechanism with double output ports is proposed to amplify the microstroke of piezostacks with a relatively high resonance frequency. Two pilot sliding spools are differentially actuated moving the main spool back and forth, modulating the flow rate and direction. The coupling dynamics of the piezohydraulic valve is also formulated on the Laplace domain with the concept of two-port dynamic stiffness model and control theory. The influence of key structural parameters on the flow characteristics is analytically calculated, and the optimal static and dynamic performances are obtained. The theoretical prediction is in reasonable agreement with the experimental results in the closed-loop control, proving that the operational concept is viable.