An SMA Wire-based Tendon Actuator and its Application on Robotic Fingers

Towards a wider application of Shape memory alloy (SMA) driven actuators, by following the principle of easy assembly and applicable design, a novel design of tendon-driven actuators for robotic and wearable devices is presented. The actuator is driven by a group of SMA wires which is enhanced by wrapping layers of Teflon and copper for better insulation and heat dissipation while retaining the characteristic of easy manufacturing. As a demonstration, a multiple SMA wire-driven tendon robotic finger, which utilizes the actuator on agonist-antagonist muscle pairs without any bias strings, is presented. The demonstrating device is built by a combined group of LEGO Technic bricks and custom 3D-printed blocks. A real-time control and sensor circuit system is designed based on IIC bus sensors, including a 6-DoF inertial meter and an ADC for a rotational encoder, for evaluating the demonstrating device. The result of the experiment shows that our design exhibits a superior performance, on both fast-actuating speed and relaxing speed, when compared to conventional SMA wire-based robot fingers.