Design and development of a high pumping frequency piezoelectric-hydraulic hybrid actuator

This paper describes the design and development of a piezoelectric-hydraulic hybrid actuator operating at a high pumping frequency. The actuator is envisaged as a potential actuator for a trailing edge flap on a full scale smart rotor system. While recent research efforts based on the same concept have investigated actuators with large piezoelectric stacks operating at a relatively low pumping frequency, the goal of the present work is to investigate the behavior of the actuator at a low volumetric displacement and high pumping frequency. Preliminary design of the actuator system is carried out, and the dependence of the performance of the actuator on various system parameters is identified. This enables the optimum selection of geometric parameters and piezostack characteristics for a given external load. Challenges to achieving high pumping frequencies were identified and solutions were implemented. The actuator was driven by two piezostacks, of a total length of 36mm and cross-sectional area 100mm(2). The actuator was tested up to a pumping frequency of 1 kHz, developing a maximum no-load velocity of 1.2 in/s and a blocked force of 35 lb in the unidirectional output mode. Bidirectional output performance was also measured, by incorporating a 4-way valve in the hydraulic circuit. At a frequency of 5 Hz, a no-load output displacement with an amplitude 32mils was measured.