Finite element analysis of the uniformity of magnetic field for on-off Giant Magnetostrictive Actuators

Giant magnetostrictive material (Terfenol-D) is a new kind of functional material driven by magnetic-field. Under normal temperature, it has many merits including high strain, big output force and quick response, etc. That makes giant magnetostrictive actuators (GMA) have extensive application on electromagnetic-devices or MEMS such as precise positioning of machine tools, optical systems, micro pumps and active vibration control. Commonly, a solenoid coil, driven by an external power supply, surroundes the GMM rod and provides the necessary field. Accordingly, the intensity and uniformity of the magnetic field are the key factors that influence the performance of GMA. This paper proposes an on-off type GMA with a close magnetic circuit structure. To analyze and improve the uniformity of magnetic field, finite element method (FEM) is adopted to analyze different magnetic circuit configurations. Results of different models are compared and lead to an optimized design of the magnetic circuit. And a multi-section solenoid driven by multi-current is proposed and analyzed. Based on the analysis, a prototype and a test bench are set. Phi F14times38.5 mm GMM rod is used and the static displacement of the GMA is 38.3 mum.