Sensorless Control of a Novel Linear Magnetostrictive Motor

In this paper, the sensorless control of a novel linear magnetostrictive motor is presented. We developed this low-power linear magnetostrictive motor with local three-phase excitation. In response to a traveling magnetic field inside the Terfenol-D active element, it moves in the opposite direction with a peristaltic motion. It is observed that there is a direct relationship between the active element´s position and the coils´ inductances. To detect the inductance change, the coil´s current response to a pulse voltage input is monitored. Then, a fundamental relationship between the coils´ current-response pulsewidths and the active element´s position is experimentally developed. Eventually, the closed-loop sensorless control of the linear magnetostrictive motor was successfully performed. The sensorless control demonstrated the position-estimation capability with a ±1-mm maximum error.