Integrated Multicomponent Modeling and Optimal Design for Antagonistic Shape Memory Alloy Bending Joint

Shape memory alloys (SMAs) are highly suitable for flexible and soft robots due to their lightweight nature, high power density, and miniaturization potential. However, the design of SMA-based continuum bending joints for robotic applications is often restricted by the inherent trade-offs in their mechanical characteristics. In this work, we present an integrated multicomponent framework that encompasses four submodels, including bending angle, load-deflection stiffness, distal twisting angle, and output force for antagonistic SMA wire bending joints. The framework unifies all submodels under a common temperature input set and systematically clarifies their coupled relationships, providing quantitative insight into their trade-offs. A model-based optimal design methodology is then developed for the SMA bending joint, balancing the different mechanical performance metrics to deliver an optimal joint design that satisfies the task requirements. Experiments on the SMA bending joint with optimal design parameters validate the accuracy of various submodels. Two additional nonoptimal prototypes were experimentally evaluated against the optimized design, validating the feasibility of the proposed optimal design methodology. The integrated multicomponent modeling framework and optimal design methodology address the intricate coupling effects inherent in antagonistic SMA wires, minimizing the need for iterative prototyping and facilitating the adoption of SMA wires in flexible and soft robots.