A Variable Stiffness Soft Actuator for Hand Rehabilitation

Stroke patients have a pressing demand for innovative hand rehabilitation devices with multiple finger joint positions. In this research, a novel soft variable stiffness actuator is proposed for alternative hand rehabilitation therapies. The design allows targeted stiffness modifications above specific joints, enabling a range of motions from a simple actuation source, supplemented by a smaller actuator determining internal stiffness. Four configurations were tested, adjusting stiffness regions within the actuator. Initial testing employed Finite Element Analysis simulations with hyper-elastic non-linear material settings, predicting actuator behavior under varying pressure. Comparison of simulation and experimental results, despite differing actuation pressure due to air leaks, revealed an acceptable replication of Finite Element Analysis simulations, with minor differences in tip trajectory. Validation involved testing a single prototype, laying the groundwork for a new form of variable stiffness actuator. The results indicate that the proposed soft variable stiffness actuator can achieve diverse hand rehabilitation guidance postures under the desired force, making it applicable to next-generation hand rehabilitation gloves and other devices.