Experiments on the audio frequency response of shape memory alloy actuators

The small-signal frequency response of Shape Memory Alloy (SMA) actuator wire was inves-tigated in this paper, as a prelude to developing an improved motion controller for robotic ap-plications. A series of experiments were carried out, in which SMA wires were heated at fre-quencies of up to 2 kHz under a variety of dif-ferent tensions and thermal histories. The wire was connected to a diaphragm, so that small motions of the wire would produce acoustic emissions, which were detected and measured using a sound meter. The results show that the wire can respond at frequencies as high as 1 kHz, which suggests that a high-bandwidth motion controller is feasible. Given the high frequencies used in this experiment, some at-tention was paid to demonstrating that the ob-served behaviour is attributable to the shape memory effect.