A parallel ankle rehabilitation mechanism and its performance analysis based on 3-UPS/RRR

Based on the physiological anatomical structure and movement characteristics analysis of human ankle joint, a 3 degree of freedom (DoF) 3-UPS/RRR ankle rehabilitation parallel mechanism is presented. Its three active branched chain inclination arrangement avoids the singular configuration of the mechanism and meets the required ankle rehabilitation workspaces. By means of constraint branches and the moving platform, the mechanism center of rotations matches the patient's ankle center of rotations. Inverse kinematics is solved analytically velocity Jacobian matrix and statics Jacobian matrix are established, and mechanism workspace is coped with. Moreover, in view of Jacobian matrix, kinematics performance and statics performance of the mechanism are analyzed and simulated. The result shows that the mechanism is of favorable operability, flexibility, and stiffness characteristics, and its torque transmission is within the specified workspace. Lastly, inverse dynamics equations of the mechanism are modeled by Newton-Euler formulation; the relationship among driving forces, constraint forces and motion parameters are obtained. A computational example is provided.