A new servo motor using shape memory alloy

A light and high-torque servo motor using SMA (shape memory alloy) is presented. Its design method is derived using the dynamical properties of SMA and the geometrical relationships of the SMA motor. A fixed-ring-type SMA motor with a synchronous belt was designed, and its torque and maximum rotary speed were calculated. In a trial production, a fixed-ring-type SMA motor with a synchronous rod (similar to the synchronous belt type) was manufactured. The characteristics of this SMA motor were compared with the values of an ultrasonic motor and two direct drive motors. It is concluded that the static characteristics of the SMA motor are comparable to those of the ultrasonic motor, but its dynamical characteristics are very poor