Energy-saving and quickly-responding SMA actuator

Abstract

Abstract. The main drawbacks of SMA actuators are a slow response and a waste of electric power. The power should be continuously supplied for SMA elements to remain austenite state until the actuator begins to take the other position. The problems are more serious when batteries and thick SMA elements are used. We propose a new SMA actuator which consumes little energy and responds very quickly. The actuator consists of a specially designed bias spring and two SMA elements which exert the force in opposite direction to each other. The bias spring, unlike a common spring which has one stable position, has two stable positions. A SMA1, for instance, contracts on heating by electricity, the actuator takes one stable configuration. No further power supply is necessary to maintain the stable position, providing enough time for the SMA1 to cool. When the other SMA2 is heated, it contracts with enough force to move the bias spring and to expand the already-cooled SMA1. Power supply stops immediately after the actuator takes the other stable configuration, causing power saving and quick response.

Elastic compensation of linear shape memory alloy actuators using compliant mechanisms

“…The first article of this kind can be traced back to the study by Ishii and Ting (2004) in which two antagonistic SMA springs are coupled with a negative stiffness compensating elastic spring. Jee et al (2009) published a similar idea and proposed a smart activation strategy of the SMA springs, which drastically reduces the energy consumption and shortens the actuation time of the device. Beginning with the study by Plante et al (2005), other compensating architectures have been proposed lately in the field of dielectric-elastomer actuators (Berselli et al, 2009; Chouinard and Plante, 2011; Plante and Dubowsky, 2008).…”

“…To remove this limitation, this article proposes a modular two-SMA actuator compensated by compliant mechanisms (see Howell, 2001, for a review). The specific architecture addressed was inspired by a compensating device first proposed by Plante et al (2005) in the field of dielectric-elastomer actuators and by Jee et al (2009) in the category of SMA actuators. The basic module of the actuator comprises four identical flat beams with hinged ends, compressed axially beyond their buckling limit (Figures 4 and 5).…”