Kinematic Performance Analysis and Optimization of a 3-DOF Parallel Mechanism for Ankle Rehabilitation

The rotation center of the existing ankle rehabilitation robot is inconsistent with the actual rotation center of the human ankle, which will influence the rehabilitation effect. This paper proposes a 3-DOF parallel mechanism for ankle rehabilitation based on a UR equivalent model with respect to the physiological structure and motion characteristics of the human ankle. The inverse kinematics of the mechanism is established in terms of the analytical method. The workspaces of the mechanism are obtained by the search method and compared with the motion range of the human ankle, which shows that the mechanism could meet the motion demand of ankle rehabilitation. To make the mechanism have an excellent kinematic performance within the rehabilitation motion range, the ratio of the high-quality transmission workspace is greater than 0.5 as the optimization goal, the parameters of the mechanism are optimized based on the motion/force transmissibility. The results show that the mechanism can meet the motion requirements of ankle rehabilitation and have an excellent kinematic performance in its rehabilitation motion range.