Comprehensive Numerical Analysis of a Four-Way Two-Position (4/2) High-Frequency Switching Digital Hydraulic Valve Driven by a Ring Stack Actuator

This paper presents a feasibility study using a commercially available ring stack actuator to develop a four way-two position (4/2) high frequency switching digital hydraulic valve. The excellent characteristics of multilayer piezoelectric actuators, such as a simple design, reduced moving parts, high reliability, and fast response, make them ideal for constructing this type of digital hydraulic valve. High frequency switching digital hydraulic valves (HFSVs), indeed, must be able to switch from fully open to fully closed positions in less than 5 ms, while maintaining minimal pressure losses and delivering large flows. The proposed valve architecture is assessed using well-established equations implemented in a Simulink model, allowing the hydraulic, mechanical, and electrical parts of the valve to be accurately simulated. The paper first provides a detailed description of the numerical model. Next, the hysteresis model of the ring stack actuator is validated against the data provided by the manufacturers on their website. Finally, the numerical results obtained with both open-loop and closed-loop control systems are presented. The simulations show that at a switching frequency of 200 Hz with maximum amplitude and duty cycle of the input pulse digital signal, the valve exhibits high average flow rates (~60 L/min), low average power consumption (~1500 W), and maintains a pressure drop of only 15 bar. Moreover, the simulations reveal that the control system is very effective since the valve switching time is within 1 ms.