Design of a Shape Memory Alloy Coil Actuated Robotic Finger with Compliant Joint Antagonists

This thesis investigates the development of a 3D-printable finger with compliant joints actuated by shape memory alloy (SMA) coils. This work presents the design, manufacturing, and characterization of the compliant finger mechanism, the SMA coil actuators, and an integrated prototype from analytical and experimental methods. The compliant finger mechanism is 3D-printed using thermoplastic polyurethane. Characterization of the mechanism exhibits a hysteresis profile in the force-displacement domain. The SMA coils are designed using a static two-state model, based on the required actuation stroke at discrete force-displacement coordinates. SMA coils are manufactured and characterized to obtain the actuator profiles for the SMA. The experimental profiles for the actuator and structure are used to predict equilibrium points between the two hysteresis curves. The final assembly with an SMA coil actuating the compliant mechanism is tested, and the experimental results show the actuation stroke and bias distance match the predictions from the hysteresis analysis.