Motor-driven Giant Magnetostrictive Actuator

Traditional giant magnetostrictive actuator (GMA) uses current in the coil to alter the output strain. The current should be maintained all the time to keep a constant output. The mechanical ouput is zero and the input power is consumed on the resistance of the coil. The efficiency of the GMA is near zero at this condition. At low working frequency, such as tens of Hz, the efficiency of traditional GMA is often low. To resolve this problem, we propose a novel motor driven GMA.This motor driven GMA does not use coil to drive the magnetostrictive magerial. It uses a rotary permanent magnet to drive the magnetostrictive material. The motor driven GMA only keeps stop position to maintain a constant output strain. The motor does not need any input power so that the efficiency can be higher than the traditional GMA at this condition. The output strain can be continously adjusted by rotating the permanent magnet. The theory and experiments have proved the concept of motor driven GMA. The paper on the motor drive GMA has been published at the journal of IEEE Transaction on Magnetic.This thesis has proved the concept of motor driven GMA based on theory and experiments. Firstly, the mathematical model by using reluctance method has been established to present the relationship between the output strain and the rotary speed of the motor. Secondly,3D finite element model has been established to present the magnetic field distribution with and without bias magnets that have different structures at different positions of the rotor. Finally, the prototype has been designed and manufactured. The experimental results are in accordance with the theory, and further prove the concept of motor driven GMA. This thesis supports the necessay theory basis and experimental results for the novel motor drive GMA.The motor driven GMA has many good characteristics, such as high efficiency at constant strain output and continuous output adjustment. These characteristics make motor drive GMA have many potential applications, such as effcient brake, precise positioning stage, precise actuator for manufacture and actuator for manufacturing piston with variable elliptical sections.