Introduction. Upper-limb exoskeletons for rehabilitation and assistive therapy must reproduce anatomically plausible motions while ensuring kinematic compatibility with the human arm to reduce parasitic joint loads, discomfort, and misalignment. Achieving this requires a systematic synthesis of mechanism topology and geometric parameters under biomechanical constraints and device-level requirements. This paper addresses the structural and parametric synthesis of biomimetic upper-limb exoskeleton mechanisms aimed at restoring motor functions after neuromuscular impairment.
Methods. A structural and parametric design framework was developed that defines target human joint trajectories and ranges of motion for the shoulder–elbow–forearm chain, generates candidate mechanism structures (serial, parallel, and hybrid linkages with redundant/self-aligning degrees of freedom), and performs parametric synthesis via constrained optimization. The objective functions include kinematic alignment error (distance between anatomical and exoskeleton instantaneous axes/centers), workspace coverage, and isotropy-related metrics, while constraints enforce joint limits, link interference avoidance, and attachment ergonomics. The optimization uses multi-objective search with penalty handling to identify Pareto-optimal solutions and robustness to anthropometric variability.
Results. The proposed approach yields families of feasible exoskeleton mechanisms that match prescribed joint kinematics with reduced alignment error across the rehabilitation workspace. Compared with baseline designs, synthesized mechanisms demonstrate improved workspace consistency and lower sensitivity to user-specific limb dimensions while maintaining compact link lengths and acceptable joint conditioning. The obtained Pareto set highlights trade-offs between alignment accuracy, mechanism complexity, and ergonomic constraints, providing quantitative guidance for selecting structures tailored to specific therapeutic tasks.
Conclusions. Structural and parametric synthesis enables the principled development of biomimetic upper-limb exoskeleton mechanisms that better conform to human joint kinematics and anthropometric diversity. The resulting designs are expected to improve comfort and safety and to support more effective motor function restoration through enhanced human–robot kinematic compatibility.
