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This paper presents the design, control, and validation of a soft robotic exoskeleton system, the REHAB Glove, for hand rehabilitation. The system is comprised of five hybrid soft-and-rigid robotic digits that apply controlled flexion and extension motion to fingers. The previous actuator design of the soft robotic digit was improved for kinematic compatibility with anatomical motions of the hand in relation to range of motion, center of rotation, and dorsal skin lengthening. The design was validated using motion capture and analysis. A position control algorithm, which controls finger angular trajectories (angular position and velocity), was developed based on motion sensor feedback. The operation of this algorithm was verified using a 90° digit tip trajectory with two angular velocities of 15°/sec and 30°/sec. A pilot study was carried out with five healthy individuals to evaluate the performance of the REHAB Glove in providing therapeutic schemes. The results show that the REHAB Glove is able to provide controlled motion compatible with the kinematics and dynamics of the human.

This paper presents development of a theoretical model for predicting the torque generated by a pneumatic soft-and-rigid hybrid actuator at a given actuation pressure and bending angle. The soft actuator with a novel architecture is comprised of half bellow-shaped flexible hollow structure (soft section) in-between block-shaped semi-rigid sections made of silicone rubber materials. This actuator provides forward and backward bending motion when air pressure and vacuum are applied into the soft section, respectively. A simplified steady-state model was developed based on the quasi-static assumption when the system dynamics is slow enough that all of the interacting forces comes to an equilibrium at any given bending angle during the motion. The elastomeric material was modeled using the Yeoh 3rd order model to capture its nonlinear behavior. The model was studied for the soft actuators with different geometrical features in two cases of the free end motion (without external force) and the constrained end motion (with external force). Experimental testing and finite element simulations were carried out corresponding to the case-studies to validate the model. Comparison of the results obtained by these two approaches show a good agreement with the theoretical model’s prediction.

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