Design and Optimization of an Index Finger Exoskeleton With Semi-Wrapped Fixtures and Series Elastic Actuators

This paper proposes a novel index finger exoskeleton with semi-wrapped fixtures and elastomer-based clutched series elastic actuators. The semi-wrapped fixture is similar to a clip, which improves the convenience of donning/doffing and connection stability. The elastomer-based clutched series elastic actuator can limit the maximum transmission torque and improve passive safety. Second, the kinematic compatibility of the exoskeleton mechanism for the proximal interphalangeal joint is analyzed, and its kineto-statics model is built. To avoid the damage caused by the force along the phalanx, considering the individual difference in the size of the finger segment, a two-level optimization method is proposed to minimize the force along the phalanx. Finally, the performance of the proposed index finger exoskeleton is tested. Statistical results indicate that the donning/doffing time of the semi-wrapped fixture is significantly less than that of the Velcro. Compared with the Velcro, the average value of the maximum relative displacement between the fixture and the phalanx is reduced by 59.7%. Compared with the exoskeleton before optimization, the maximum force along the phalanx generated by the exoskeleton after optimization is reduced by 23.65%. The experimental results show that the proposed index finger exoskeleton can improve the convenience of donning/doffing, connection stability, comfort, and passive safety.