Abstract: For the patients who are suffering the ankle injuries especially for the hemiplegic after stroke, the ankle rehabilitation is one of the very difficult problems. A novel decoupled parallel mechanism used for ankle rehabilitation is presented aiming at this background. Based on the tractive therapy of traditional Chinese medicine, the design idea that more attention should be paid on the traction function for ankle rehabilitative mechanism is introduced. Independent rotational rehabilitation, including dorsiflexion, plantarflexion, abduction and adduction, and rotational rehabilitation under the traction can be realized by the proposed mechanism simultaneously. By using the screw theory, the character of the degrees of freedom of the mechanism at arbitrary pose is analyzed. The forward and inverse position solutions of the mechanism are derived out, the velocity Jacobian matrix is solved, and the singularity analysis is performed. The optimization for the size of the decoupled mechanism is performed through the output parameters, and the numerical example is given based genetic algorithm, which verifies the workspace of the mechanism satisfying the requirements of the ankle rehabilitation movement.

Key words: ankle rehabilitation, decoupled, parallel mechanism, size optimization