A Compact SMA-Driven Push–Pull Module With Precise Linear Motion

Shape memory alloy (SMA) actuators have demonstrated great value in soft robotic applications; however, traditional tendon-based actuation methods suffer from hysteresis that affects control accuracy. In this article, we propose a SMA-driven push–pull module by using antagonistic actuation and rod connection, and further integrate a linear thin film potentiometer within a compact size, which can achieve precise pulling and pushing motions based on the model-based closed-loop control. The compact SMA module with a large stroke can fulfill the submillimeter position accuracy for pulling and pushing motions at varying speeds and loads. An application to a soft origami continuum robot proves that the proposed SMA module can solve the hysteresis problem, simultaneously achieving precise control of bending and contraction/expansion (RMSE$\leq$0.85 mm). It is also demonstrated that the SMA module can be MR-compatible and function well under MRI feedback. This study will contribute to the advancement of SMA actuators in precision motion control and soft robotic applications.