3UPS Parallel Mechanism for Passive Rehabilitation of Lateral Ankle Sprains in Ball Sport Athletes

This work focuses on designing and developing a 3UPS parallel mechanism for passive rehabilitation of lateral ankle sprains in ball sport athletes. The study analyzes the high incidence of this musculoskeletal injury and its functional and social impact. The proposed mechanism seeks to accurately replicate the physiological movements of the ankle through the integration of advanced inverse kinematics methods and screw theory. The required ranges of motion were defined to ensure a proper and safe recovery. The results show that the mechanism fully achieves the physiological ranges required: dorsiflexion-plantarflexion from 30° to –20°, abduction-adduction from 10° to –10°, and eversion-inversion from 20° to –10°. Moreover, the workspace analysis demonstrated adequate coverage in both positional and orientational domains, with vertical displacements ranging from 0.01 m to 0.2717 m, and maximum achievable angles of ±61.00° for ψ, from 24.77° to –18.72° for θ, and ±22.35° for φ. Likewise, the singularity analysis initially revealed 22 critical position configurations and 44 for orientation, which were reduced to 12 and 14 after eliminating redundancies. Importantly, all singularities lie outside the effective workspace. This development provides an accessible, robust, and efficient solution for improving rehabilitation and preventing future complications such as chronic ankle instability.