Performance modeling of a piezohydraulic actuation system with active valves

Abstract

Piezohydraulic actuation is the use of hydraulic fluid to rectify the high frequency, small stroke oscillation movement of the piezoceramic stack into a unidirectional movement at a specific combination of stroke and force. In recent years, piezohydraulic pumps have been studied and developed by several groups. This paper presents two steady flow models based on different approximations of the hydraulic fluid. In the first model we assume a fully developed incompressible viscous flow, and in the second model we incorporate the compressibility of hydraulic fluid into our model. These two models are derived based on the energy equations for hydraulic flow in a circular pipe. Major and minor losses are identified and incorporated into the models. Assumptions and approximations were made to minimize computation effort while achieving good accuracy. A piezohydraulic actuation system with active valves is then built and tested. Comparison with test results shows that the simulations accurately predict system performance under loads at which value leakage is not present. The results reveal that friction losses due to viscosity are a major limitation of performance for the current test setup when operating at higher frequencies. Timing studies of the active vales show the valve timing is important to the performance of the system.

Experimental Study on the Performance of a Bidirectional Hybrid Piezoelectric-Hydraulic Actuator

“…This configuration allows only a unidirectional valve opening. When the fluid flows into the chamber from the inlet valve, the outlet valve port does not allow any fluid to come into the chamber and vice versa [9]. In this research, 0.05mm, 0.08mm, and 0.15mm thicknesses of reed valve were considered for the performance experiment.…”

Study on flow distribution inside integrated hybrid actuator

“…The output velocity from the numerical analysis increased with the actuating frequency, and the velocity decreased after 35 Hz similar to the experimental results according to the flow loss because the working fluid velocity could not follow the acceleration of the piezo pump. The decrease of the operating velocity at the high frequency has been explained as due to the slow response time of the working fluid inside the chamber [11], and to the irregular flow inside the pipe [12,13]. Chaudhuri [1] concluded that the flow velocity decreased due to the fluid compression in the limited space at the high frequency.…”

Design, Analysis, and Verification of an Electro- Hydrostatic Actuator for Distributed Actuation System

“…Thanks to the development of linear drive technology, researchers can explore many related can achieve very high reciprocating motion frequency and cooperate with active or passive rectification valves to provide fluid power to the actuation system [15][16][17]. The requirements of bidirectional drive and high rectification efficiency make the active valves preferred alternatives [18,19]. The valves need to be controlled in coordination with the pumping cylinder based on the sensing of the cylinder motion.…”