Structural Design of an Assistive Training Mechanism for Ankle Rehabilitation

Abstract

To enhance the efficacy and safety of rehabilitation, this study presents a bionic ankle rehabilitation mechanism integrated with a posture-switching function. The device utilizes a parallelogram mechanism to address the challenges of sit-to-stand (STS) transition assistance. By synergizing a dual crank-linkage with a three-link parallel mechanism, the device accurately replicates natural gait trajectories and multi-dimensional ankle movements. In terms of kinematic analysis, an inverse kinematic model incorporating spatial rotation matrices was established to derive the nonlinear relationship between actuator inputs and platform pose outputs. Furthermore, instantaneous kinematic equations were extracted, providing a direct theoretical basis for subsequent rehabilitation verification. Finite element analysis (FEA) demonstrates that under an extreme load of 1500 N, the peak stress of the core structure 211.08 MPa and the resulting deformation remain well below the material’s failure thresholds. These results validate the structural reliability and clinical potential of the proposed mechanical design.