Maximizing output work of PZT stacks while gaining large displacement amplification

A novel design concept is presented for amplifying the displacement of a PZT stack over 50-fold while transmitting a significant amount of work per cycle. Piezoelectric devices, such as PZT stack actuators, have a competitive power density, while consuming virtually no energy for generating a force at a constant position. Despite the salient features, the actual work usable for activating a load is significantly reduced when displacement amplification mechanisms are used for attaining displacements large enough to drive a macroscopic robotic system. This paper addresses how the work produced by a PZT stack is transmitted to a load without attenuation. The theoretical limit of maximum work is obtained and experimentally verified. Conditions for transmitting the maximum work, i.e. maximum work transmissibility, are obtained based on a simple model. A novel displacement amplification mechanism using a flexure-free, buckling mechanism is then presented as a solution that satisfies the maximum energy transmissibility conditions. A prototype device is designed and tested. Initial experiments show promising results.