Powered finger exoskeleton having partially open fingerpad for flexion force assistance

A powered finger exoskeleton having partially open fingerpad is proposed as a preliminary study for a hand exoskeleton. The partial opening allows the central part of the wearer´s fingerpad to make direct contact with the gripped object so that the natural haptic sensation is preserved. At the same time, the remaining sides of the wearer´s fingerpad are blocked by the exoskeleton structure equipped with a force sensor. During object manipulation, the finger contact force given by the wearer is estimated from the measurement at the force sensor and is used to calculate the desired assistance force. A McKibben type pneumatic artificial muscle is used as an actuator for the finger exoskeleton. The actuator force transmission mechanism is designed to be engaged only when the wearer´s estimated finger force exceeds a certain threshold. Otherwise the finger exoskeleton passively follows the wearer´s finger motion with low resistance. An experiment of holding an object with minimum grip force was performed to verify the effectiveness of the proposed exoskeleton.