Experimental Validation of a Hybrid Electrostrictive Hydraulic Actuator Analysis

The basic operation of smart material-based hybrid electrohydraulic actuators involves high frequency bidirectional length change in an active material stack (or rod) that is converted to unidirectional motion of a hydraulic fluid by a set of valves. In this study, we present the design and measured performance of a compact hybrid actuation system driven by the single-crystal electrostrictive material PMN-32%PT. The active material was actuated at different frequencies with variations in the applied voltage, fluid bias pressure, and external load to study the effects on output velocity. The maximum actuator velocity was 330 mm/s and the corresponding flow rate was 42.5 cc/s; the blocked force of the actuator was 63 N. The results of the experiments are presented and compared with simulation data to validate a nonlinear time-domain model. Linearized equations were used to represent the active material while the inertia, viscous losses, and compressibility of the fluid were included using differential equations. Factors affecting system performance are identified and the inclusion of fluid inertia in the model is also justified.