A millimeter-Sized Robot Using SMA and Its Control

A millimeter-sized robot has been fabricated using shape memory alloy (SMA) actuators, focusing on its advantages including a strong force to weight ratio and extendibility to micro sizes. The Al links for the robot were made by wire-electric discharge machining (W-EDM). A push-pull type SMA actuator has been constructed with a couple of SMA sheets, each 50<I>μ</I>m thick, which were cut by using a laser beam. They were set on Al links after they had been bent spirally. The dynamics of a larger-size SMA actuator were analyzed theoretically and experimentally. This theory was then applied to estimate the dynamics of the millimeter-sized SMA actuator proposed here. The joint angle was controlled with and without the sensor feedback.