CABLEAnkle: A Cable-Driven Approach to Assisted Ankle Rehabilitation

Introduction

Effective rehabilitation of the ankle joint is critical for maintaining mobility and functional independence, particularly among elderly individuals and patients undergoing post-injury or post-surgical recovery. Many existing robotic rehabilitation devices rely on rigid mechanical architectures, which may increase weight, reduce adaptability, and compromise user comfort. Cable-driven actuation offers a flexible and lightweight alternative, capable of safely assisting complex joint motions. This work introduces CABLEAnkle, a cable-driven device developed to support assisted and rehabilitative ankle movements.

Methods

CABLEAnkle consists of a foot-shaped platform actuated by four Dynamixel servo motors that modulate cable tension routed through a knee-mounted brace. The mechanical architecture is designed to reproduce the three primary rotational degrees of freedom of the ankle: dorsiflexion/plantarflexion, inversion/eversion, and adduction/abduction. A detailed CAD model was developed to define geometry, cable routing, and motor placement. Kinematic modelling was carried out to relate motor rotation to cable length variation. Finite element analysis was performed to assess the structural feasibility of a lightweight PMMA foot platform under representative loading conditions. A preliminary prototype was then assembled.

Results

The kinematic analysis confirmed that coordinated cable actuation enables physiologically relevant ankle rotations. Structural simulations demonstrated that a 5 mm thick PMMA platform withstands symmetric and asymmetric loads representative of assisted ankle motion without exceeding material stress limits. The assembled prototype successfully reproduced the intended ankle movements, validating the feasibility of the proposed mechanical and actuation design.

Conclusions

The results demonstrate that CABLEAnkle is a compact, lightweight, and adaptable cable-driven solution capable of replicating essential ankle kinematics. The proposed design provides a promising foundation for future experimental validation and clinical evaluation in rehabilitative and assistive applications.