A novel motion-coupling design for a jointless tendon-driven finger exoskeleton for rehabilitation

• A new motion coupling plan for joint-less hand exoskeleton was proposed.
• Avoiding the drawback of traditional plan, producing correct motion tendency
• Can facilitate the hand therapy process into patients' daily lives
• The entire structure is compact and lightweight, and can be arranged in a glove.
• 17.5%–37% input tendon force can be converted into output force.

We have designed a new jointless tendon-driven exoskeleton plan for the human hand that provides a correct and stable motion sequence while keeping the structure lightweight, compact and portable. Before the development, anatomy analysis and a kinematics study of the human finger were performed, and bending angle relationships among the metacarpophalangeal (MCP), proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints were analyzed. Detailed implementation is discussed, including the basic theory of the joint motion coupling method, related formula derivations and mechanical design of an experimental device. An experimental setup was built, and series of experiments was conducted to examine and evaluate the developed joint motion coupling plan.The results indicated that the new plan worked correctly as desired, that an incorrect finger motion sequence did not occur and that the new coupled tendon driven plan can drive finger bending as naturally as a human. The compactness and light weight of the entire structure of the device means that its parts can be arranged for a hand glove or fingerstall more easily than most bar-linkage exoskeleton structures.