A Rotary Actuator Using Shape Memory Alloy (SMA) Wires

This paper presents the conceptual design, operating principle, simplified geometric model-based parametric analysis, experimental driving characterization, and working performance verification of a rotary actuator using shape memory alloy (SMA) wires. To achieve the research goal for developing a bidirectional SMA rotary actuator with high-torque capability, the actuator is realized with a rotational driving mechanism devised on the basis of the operating principle of wobble stepping motors. In the proposed actuator, this driving mechanism consisting of an involute gear set and crankshafts suitably and effectively functions to convert expansion and contraction of the SMA wires to high-torque rotational motion. In designing the actuator, the analysis result on parametric effect is utilized, and driving characterization and working performance verification are experimentally carried out with a fabricated functional prototype. With the experimental results, differentiating characteristics related to the operating principle of the proposed actuator and the thermomechanical behavior of SMA elements are investigated and discussed.