Power-Saving Drive of Giant-Magnetostrictive Actuator (Reduction of Displacement Fluctuation due to Magnetization of Interior Permanent Magnet)

Abstract

For the purpose of reduction of the electric power consumption during expansion of a giant magnetostrictive actuator (GMA), the authors developed the power-saving drive GMA, and showed its good power-saving performance. However, due to its drive principle, the developed GMA has a problem that instantaneous excessive expansion appears at the beginning and end of the GMA expanding. For the reduction of the excessive expansion, this paper clarifies the cause of the excessive expansion and presents the modified actuator construction. In order to prevent the giant magnetostrictive material (GMM) from being magnetized by the external magnetic field generated by the coil, the coil in the GMA is divided into two coils, and each coil is placed inside and outside of the permanent magnet. With the two coils, this paper presents two types of improved power-saving drive method. One is to counterbalance the magnetic field in the GMM actively by the magnetic fields of the coils which counter each other. The other is to actively prevent the instantaneously changing magnetic field from penetrating the GMM by the inductance of the short-circuited coil. The evaluation of performance of those methods has been carried out. It has been confirmed that both the methods are effective to reduce the instantaneous excessive expansion.