A shape memory alloy actuated anthropomorphic prosthetic hand: Initial experiments

This work presents the design and implementation of an anthropomorphic prosthetic hand actuated using shape memory alloy (SMA) wires. SMAs were chosen as the actuator for their advantages over conventional motors. The prosthetic hand has articulated fingers with torsion springs embedded within the joints. These springs provide the necessary bias force for SMA contraction as well as open the hand for relaxation. Thin SMA wires were selected for fast cooling and a bundle of eight wires was constructed to provide sufficient force and excursion for grasping. The actuator design using cables, SMA wires and springs has the advantage of providing actuation with a fewer number of cables and separate SMA wires thus requiring a simpler control scheme with fewer control inputs as well as less power consumption. The SMA wires were heated using a square pulsed input with a 71% duty cycle. Initial experiments show promising results for response, flexion and recovery times.