The Rotary Magnetostrictive Motor: a Promising Solution for Low Power Actuators


This paper contains a theoretical and experimen-tal study on rotary magnetostrictive motor, performed with the purpose of determining the optimal conditions of opera-tion. The two main types of magnetostrictive motors known from the literature, inchworm respectively resonance pre-sent the advantage of large and accurately controlled devel-oped torques for low speed values. The electromagnetic torque developed by the rotary magnetostrictive motor be-ing proportional to the frequency of the current circulating through its inductor, became the subject of frequency con-trol methods. This fact lead to the idea of controlling the torque by controlling the frequency of the current, with direct implication in the domain of torque-controlled drives. Although the actuator represents the central part of any magnetostrictive device, the entire magnetic circuit configu-ration determines the position of the permanent magnet operating point on the linear portion of the magnetostrictive characteristic. The paper includes two different methods, applied for the permanent magnet operating point alloca-tion. The magnetostrictive torque was determined and ex-pressed as function of time, for the full cycle of the periodi-cal current carried by the actuator’s coil. The cycle of the magnetostrictive torque is identical with the cycle of the periodical current circulating through the coil of the actua-tor. The analytical mathematical model developed and pre-sented in the paper considers both regimes, starting and running, making possible the tracking of the operation point. Furthermore, was possible to determine the moment of separation between the rotor disk and the flexible friction element. Several acquired data, recorded at different values of power supply frequency, demonstrate a good correlation between the theory and experiment. images