A millimeter-stroke piezoelectric hybrid actuator using hydraulic displacement amplification mechanism

Although piezoceramic actuators can generate extremely large forces, they normally exhibit small strokes in the range of tens of micrometers. A typical method to amplify these small strokes without sacrificing bandwidth has been to utilize a flexure-based leverage mechanism, where a piezo stack actuator deforms a specially cut metal block. In this paper, a new high-stroke piezoelectric actuator is presented, that employs a hydraulic amplification mechanism with a cylindrically shaped fluid chamber having a small opening at one side and a large opening at the other. When the piston in the larger opening is pushed by a piezo-stack actuator, the fluid is pressurized and pushes a shaft in the small opening through a longer distance. The stroke is determined by the area ratio of the two openings. Experiments showed that this new type of actuator could generate a longer stroke in the range of a few millimeters with a force of a few Newtons.