Design and Performance Analysis of 3RSS/S Ankle Rehabilitation Robot

Background/Objectives: Ankle rehabilitation robotics has garnered a lot of interest because of its ability to improve therapeutic outcomes and enable quantitative patient monitoring. The ankle has a complex biomechanical system, so the design needs to have accurate kinematics, structural stiffness, and biomechanical compatibility. This paper deals with the design and performance analysis of a 3RSS/S parallel robot for ankle rehabilitation. Methods: A multi-objective optimization framework is presented for simultaneous optimization of workspace volume, kinematic accuracy and structural stiffness. The topology of the 3-DOF parallel mechanism is presented, and its geometric model and Jacobian matrix are derived. The optimization problem is solved using NSGA-II and the compromise solution is selected using TOPSIS. Results: For the adopted geometric, joint and actuator-compliance models, the chosen design yields an orientation-workspace measure of WV=0.1342rad3, a global Jacobian-conditioning index of ηJ=1.0812 and a global stiffness-conditioning index of ηS=1.1874. Numerical verification shows that the prescribed clinical orientation range is covered, that the clinical workspace volume Vclinical=0.1275rad3 is strictly contained in the reachable workspace, and that the chosen solution is insensitive to the assumed geometrical tolerances. Conclusions: These simulation-based results motivate prototype development and subsequent experimental kinematic, stiffness, safety, and human–robot interaction validation.