Application of giant magnetostrictive materials to positioning actuators

Giant magnetostrictive materials have drawn a lot of attentions because of their unique features. It is well known that the performance of a device using giant magnetostrictive material is affected by a preloading applied to the material. The paper presents an approach to monitoring and controlling the preloading in a compact giant magnetostrictive positioner. The proposed method not only provides a means to make a precise measurement of the preloading but also constitutes a sensing capability with which a displacement of the positioner itself can be measured. The positioner's structure as well as basic performances are described. The paper also presents a new design of the positioner so that the effect of Joule heat can be kept minimal. Finite element analyses are conducted in parallel to the design modification in order to make-sure that the giant magnetostrictive element can be driven in an efficient manner.