Integrated Design of a Modular Lower-Limb Rehabilitation Exoskeleton: Multibody Simulation, Load-Driven Structural Optimization, and Experimental Validation

Lower-limb rehabilitation exoskeletons must balance biomechanical compatibility, structural safety, and low mass to enable practical, repeatable gait assistance. This paper proposes a planar pantograph-derived exoskeleton leg driven by a Chebyshev Lambda linkage and develops an integrated workflow from mechanism synthesis to manufac-turable optimization and experimental verification. A mannequin-coupled multibody model was built in MSC ADAMS to evaluate joint kinematics, end-point (foot) trajec-tories, and joint reaction forces under multiple scenarios (fixed-frame, ramp, stair as-cent, and inclined-plane walking). The extracted joint loads were transferred to a par-ametric finite element model in ANSYS Workbench, where response-surface surrogates and a multi-objective genetic algorithm (MOGA) were used to minimize mass under stiffness and strength constraints. For the optimized load-bearing link, the selected minimum-mass design reached a component mass of 0.542 kg while respecting the imposed structural limits, i.e., a maximum total deformation below 0.2 mm and a maximum equivalent (von Mises) stress below 55 MPa (e.g., ~0.188 mm deformation and ~39 MPa stress in the optimal candidate). A rapid prototype was manufactured by 3D printing and experimentally evaluated using CONTEMPLAS high-speed video tracking, providing measured XM(t) and YM(t) trajectories and joint-angle histories for quantita-tive comparison with simulations via RMSE metrics.