Design of Preloaded SMA-Driven Soft Robotic Limb With Onboard Thermal Sensing

This paper presents a mechanical and sensing framework for enhancing the performance of Shape Memory Alloy (SMA) actuated soft robotic systems. A novel double-helix exoskeleton structure is presented, experimentally validated to provide an optimal SMA preload range of 2.05 N to 3.63 N. This consistent tension significantly reduces actuation uncertainties and maximizes stroke. Another contribution is an onboard thermal sensing system capable of providing real-time temperature feedback without compromising the limb's compliance. The onboard thermal sensing system compares a single non-contact IR sensor against multiple thermocouples, demonstrating that IR sensing provides higher onboard accuracy and consistency while being significantly simpler to integrate and immune to compliance/detachment issues. These contributions lay the groundwork for more predictable and controllable SMA-based actuators, supporting the future implementation of data-driven models to improve locomotion control and state estimation in soft robotic platforms.