Closed loop control for shape memory alloy actuators

This paper describes design considerations of a control circuit for adaptive hybrid structures. These consist of a fiber-reinforced lightweight structure with a thermoplastic matrix and additional shape memory alloy wires, which can be used both as actuators and sensors. In order to use their properties, a control circuit able to heat the actuator wires and to measure their electrical resistance when used as a sensor is needed. In contrast to most references using expensive lab test equipment, a small sized, stand-alone control box is presented. It combines advantages of precision linear current sources for resistance measurement with high efficiency switch-mode converters delivering the wire heating current.