Design of a New 3-UPU/S Parallel Ankle Rehabilitation Mechanism

Ankle injuries may lead to severe complications, including chronic instability and reduced mobility. Rehabilitation therefore plays a critical role in restoring normal ankle function and preventing long-term impairment. However, conventional manual physiotherapy presents several limitations, such as limited availability of therapists, variability in treatment, and reduced accessibility for home-based rehabilitation. Consequently, significant research efforts have been devoted to the development of robotic and mechatronic devices for ankle rehabilitation. In this work, we propose the design of a simple and cost-effective parallel mechanism dedicated to ankle rehabilitation. The proposed device is based on a closed-chain kinematic architecture capable of reproducing the three principal rotational degrees of freedom of the ankle joint. This configuration enables controlled and repeatable rehabilitation exercises while ensuring mechanical stability and compactness. Furthermore, the device is designed to allow patients to perform rehabilitation exercises autonomously, without the continuous assistance of a physiotherapist, both in clinical environments and in home-based rehabilitation settings.