On piezoelectric super-helix actuators

Theoretical designs of piezoelectric ceramic helical and spiral actuators have existed for many years. The main reason these devices have not achieved widespread recognition and use is the perceived difficulty of processing such forms. These processing problems, covering both the material form itself and electrode placement, have been tackled and solved over recent years at the University of Birmingham. A new type of complex piezoelectric spring-type actuator has arisen as a result of this work, which takes the form of a super-helix, and is known as a wound helical electrically reactive mechanism (WHERM). This actuator structure shows a great deal of versatility in terms of the device parameters, which can be tailored to suitable applications. We show here that the geometry of this actuator effectively provides for an efficient method of amplifying the small strain produced in a piezoelectric material in exchange for a proportional reduction in maximum force holding ability. Devices shown exhibit peak no-load displacements of over +/-3 mm, with a force holding ability of up to 0.2 N, and with a total circular footprint of less than 45 mm in diameter. (C) 2002 Elsevier Science B.V. All rights reserved.