High-Gain, High Transmissibility PZT Displacement Amplification Using a Rolling-Contact Buckling Mechanism and Preload Compensation Springs

A novel design concept of piezoelectric actuators producing large displacement while transmitting a significant amount of energy is presented. A rolling-contact buckling mechanism with a novel preload mechanism can amplify the PZT stack's displacement on the order of 100 times while transmitting several times larger work output than conventional flexure-type displacement amplification mechanisms. Existing displacement amplification mechanisms are analyzed in terms of transmissibility and are characterized with two lumped-parameter elements: serial and parallel compliances. The maximum transmissibility is attained when the parallel stiffness and the serial compliance are zero. An existing flexure mechanism using structural buckling, that produces a large displacement but a low transmissibility, is replaced by a rolling-contact mechanism that approaches the maximum criterion. Furthermore, a mechanism is presented to apply a constant preload to each PZT stack despite their movement. A prototype has been built to implement the design concept and verify the theoretical results. Experiments using the prototype demonstrate that it produces a 4.2 mm free displacement with over 60% transmissibility.