Antagonistic Shape Memory Alloy Actuators in Soft Robotics

Abstract

The paper presents research concerning the utilization of shape memory alloys in terms of an antagonistic actuator system. The main focus is to determine arrangements for the necessary movements and also to evaluate a suitable control methodology. Most use cases of soft robotics can be accomplished by either linear actuators (cf. earthworm), circular actuators (cf. brachial joint) or a combination of both. Hence, for the research, those two scenarios were taken into account. The paper describes the used simulation model, which bases on a thermo-mechanical submodel of a single SMA actuator. It complements interconnections of physical parameters like temperature, percentage of martensite, elongation and tension. Furthermore, it is shown, how the submodels are connected in a suitable way to establish the required use cases.The position control of either the transversal position or the angle is realized by a PID or PI controller. The paper also shows the impact of parameter changes in the SMA on the achievable position accuracy. Also different strategies for controller design will be discussed.