Design and Experimental Study on a Hand Function Rehabilitation Exoskeleton Driven by Shape Memory Alloy Wires

To address the issues of high weight, poor human-machine compatibility, and low comfort of wearable hand function rehabilitation robots, a hand function rehabilitation exoskeleton structure driven by shape memory alloy (SMA) wires is proposed. Based on the analysis on hand physiological structures and musculoskeletal motion mechanisms, the contraction characteristics of SMA wires are combined to simulate the actuation principle of muscles and tendons. A range extender with displacement amplification pulley block based on flat SMA wire is designed, and human-machine coupling kinematic and static models are constructed. A PSO-BP-PID (particle swarm optimization-backpropagation-PID) control method based on SMA wire resistance feedback is established. A wearable hand function rehabilitation exoskeleton prototype driven by SMA wires is developed, with a mass of only 166 g. Its motion performance, grasping ability, and working temperature are experimentally tested. Experimental results show that the maximum bending angle of the exoskeleton reaches 160°, and the average fingertip force is approximately 6.5 N. The PSO-BP-PID control demonstrates better response speed and control accuracy compared to traditional PID methods. Grasping actions can be completed on various common objects through coordinated finger movements, meeting the requirements for daily rehabilitation assistance.