New “HAPA”, “FTA” and “HD-FTA” Piezoelectric Actuators

“HAPA” stands for High-Authority Piezoelectric Actuator, which describes high-performance piezoelectric actuators of large stroke and blocking force. “HAPAs” are made possible by high-bending-stiffness connectors that connect multiple units of piezoceramic stacks into a 2-level actuation structure. Present HAPA actuators are fitted with commercial piezoceramic stacks. For instance, a “HAPA-(2+2)” comprises 4 lead zirconate titanate (PZT) stacks, 2 in the upper level with displacement projecting upward and 2 in the lower level with displacement projecting downward. They not only double the axial displacement of individual stacks with only fractional increase in device length but also are of 1.5 to 3 larger blocking force depending on the actual design. “FTA” stands for Flextensional Actuator, in which the horizontal extensional displacement of PZT stacks is amplified to yield much larger contractional vertical displacement via a diamond-shaped elastic frame structure. A range of new FTAs has been developed by us using single or multiple units of PZT stacks, of which the performances are described in this work. “HD-FTA” stands for HAPA-Driven Flextensional Actuator, in which HAPA piezoelectric actuators are used as the motor section to drive diamond-shaped elastic members of various designs for further displacement amplification. Several HD-FTAs, driven by a HAPA-(2+2) actuator, have been developed. Compared with standard FTAs of comparable stroke, HD-FTAs display a higher working load but of smaller overall length. “HAPA”, “FTA”, and “HD-FTA” piezoelectric actuators find applications when a smaller actuator length is advantageous in addition to the required moderate-to-large displacement and working load.