Design and modeling of a hybrid soft-rigid hand exoskeleton for poststroke rehabilitation

Poststroke patients’ need for hand rehabilitation is urgent since hand plays a significant role in people's activities of daily life (ADLs). Contrast to traditional rigid devices with excessive stiffness and soft devices lacking well-understood models, we present a hybrid soft-rigid exoskeleton (HSRexo) for poststroke hand rehabilitation adopting the simplified three-layered sliding spring (sTLSS) mechanism that combines the intrinsic compliance and comprehensible kinematics. The compliant spring blades in the sTLSS mechanism make it possible to compactly actuate three natural flexion/extension of finger joints by only 1 ° of freedom (DOF). To deal with the nonlinear deformation of soft elastic elements, the modeling of the sTLSS mechanism is proposed by the pseudo-rigid-body model (PRBM) method to achieve comprehensible kinematics and optimize design parameters. Finally, the simulation and preliminary prototyping demonstrate the accuracy of the model and the compliant natural flexion/extension joint angle of the HSRexo design due to the modeling and optimization of the sTLSS mechanism.