Development and Pre-Clinical Validation of Tendon Driven 2 Degree-of-Freedom Powered Ankle-Foot Orthosis for Heuristic Algorithm Based on Gait Stability.

In the field of rehabilitation, Powered Ankle-Foot Orthoses (PAFO) are often used, which are wearable robots designed to rehabilitate the mobility of individuals with reduced walking stability, such as the elderly. Previous studies have developed a 2-degree-of-freedom PAFO capable of assisting both the talocrural and subtalar joints of the ankle. However, the use of pneumatic artificial muscles (PAMs) as actuators resulted in low control capacity(low cutoff frequency). To address this limitation, this study developed a tendon-driven device that offers higher cutoff frequencies through a motor system driven by cables. Furthermore, we did pre-clinical experiment, and it showed the possibility of enhancing walking stability with our heuristic-based algorithm for human-in-the-loop optimization. This algorithm was based on the activity of antagonistic muscles to those targeted for assistance at both ankle joints and walking stability was evaluated through Gaussian ellipsoid.