Design and Kinematic Performance Analysis of a Cable-Driven Parallel Mechanismfor Ankle Rehabilitation

Neurological impairment after stroke or traffic accident can lead to the disability of lower limbs and the inability of simple actions such as foot lifting. In order to recover the motion ability of the patients, a 3DoF (degree of freedom) cable-driven parallel mechanism is proposed for ankle rehabilitation. Firstly, the structure of the cable-driven parallel mechanism for ankle rehabilitation is introduced. Then, the forward and inverse kinematics are solved by using the Newton-Raphson iteration method and the closed-vector-circle method, and the velocity Jacobian matrix is established. By analyzing the driving force of each cable, tension distribution is optimized and the workspace of the mechanism is calculated. Lastly, kinematical performances are analyzed based on the Jacobian matrix. Results show that the mechanism is of no singularity, good kinematic dexterity and stiffness performance within the prescribed workspace. Furthermore, the mechanism center of rotations matches accurately with the ankle center of rotations owing to the equivalent spherical pair and the moving platform designed in this paper, which is an advantage over some existing ankle rehabilitation robots. The designed mechanism is suitable for ankle rehabilitation training.