A Rigid and Flexible Combined Finger Exoskeleton Design with Variable Curvature

Some hand exoskeletons have been used in the rehabilitation treatment of paralyzed patients caused by stroke and cerebral apoplexy as a result of research into hand exoskeletons. However, how to make the patient more comfortable to use and how to make the exoskeleton more precise are still key issues that need to be studied. Aiming at the motion law and skeletal characteristics of the human hand, this paper proposes a soft exoskeleton machine for hand rehabilitation training that combines rigidity and flexibility. Using a simplified two-layer sliding spring mechanism, the device combines the comfort and fit of a flexible device with the accurate kinematics of a rigid device. The mechanism requires only one degree of freedom to drive the normal flexion and expansion of the three finger joints. By changing the section thickness of the spring sheet to change its section moment of inertia, the bending effect of the mechanism is optimized to better fit the bending characteristics of the finger joints. To simplify the simulation of the mechanism, the method of the pseudo-rigid-body model is used to target the spring leaf’s nonlinear deformation, to achieve intuitively understandable kinematics. Finally, the accuracy of the design is demonstrated through simulation and prototype models.