A Piezo-Electric Valve Actuator for Hydraulic Exoskeleton Drives

Abstract

In many exoskeleton applications where heavy lifting is involved (e.g. in military or industrial applications) hydraulic actuators are used because of their high power density. For such applications it is necessary to develop compact and light hydraulic components so that the exoskeleton’s mass and size are low and, therefore, wearing comfort is high and power consumption is reduced to a minimum. Crucial components of hydraulic exoskeletons concerning this weight aspect are hydraulic valves and particularly their actuators, since conventional solenoids contribute the lion share of valve size and weight. As one option to solve this weight and size problem the application of smart materials such as piezo-ceramics to electrically actuate hydraulic valves are seen. The contribution at hand deals with the systematic design of a piezo-actuator which shall be used to switch a hydraulic valve. To overcome the problem of very low strain of the piezo a mechanism for amplification via a bistable buckling beam is analyzed analytically and numerically and an actuator prototype is designed and manufactured. This paper intends to carve out crucial challenges such as the requirements for snapping through of the buckling beam, the bearings of the beam and the integration of the piezo stack.