A novel meso-scale SMA-actuated torsion actuator

This paper presents our work on design, modeling, and control of a meso-scale shape memory alloy (SMA) actuated torsion actuator for miniature robots. This novel torsion actuator is bi-directionally activated by a pair of antagonistic SMA torsion springs through alternate Joule heating. First, we present the mechanical design and fabrication approach of this miniature actuator. Then, we present the torsion spring mechanical model, SMA constitutive model, and kinematic and dynamic models, followed by the derivation of the quasi-static model of the actuator. Finally, the dynamic properties are tested by step response and sinusoidal tracking tests. A model-based controller is designed and its performance is evaluated by experiments.