A New 4-DOF Robot for Rehabilitation of Knee and Ankle-Foot Complex: Simulation and Experiment

Abstract

Stationary robotic trainers are lower limb rehab robots which often incorporate an exoskeleton attached to a stationary base. The aim is to recover range of motion, increase muscles strength and reduce joint stiffness. The issue observed in the stationery trainers which involve knee and ankle-foot complex joints simultaneously is that they restrict the natural motion of ankle-foot in rehab trainings due to the insufficient Degrees of Freedom (DOFs) of these trainers. This restriction makes the joints deviate from their natural motion patterns, exerting potentially harmful forces and strain the joints. In this work, we propose a new stationary knee-ankle-foot rehab robot with all necessary DOFs including knee flexion/extension in addition to ankle plantarflexion/dorsiflexion, ankle-foot abduction-adduction and foot supination/pronation. Axes of motions are determined based on the kinematics of the joints. A typical rehab training exercise has been considered to evaluate the system performance. The chosen training (i.e., passive assistance) was first implemented in simulation to synthesize the control loop and to extract the parameters required for selecting the robot’s components. The robot was then fabricated and tested on a healthy subject. Results showed that all natural motions of the ankle-foot complex were generated during the training. Therefore, the proposed system fulfils the desired aim properly, so that it can be utilized in the design of rehab robots.

Biomechanical Effects of Adding an Ankle Soft Actuation in a Unilateral Exoskeleton

“…Moreover, in a bi-articular knee–ankle–foot exoskeleton, BF muscle activity was lower than in the powered-off condition corresponding to the assistance of knee flexion and reducing the person’s metabolic cost of walking [ 46 ]. In the case of pathological patients, therapists require them to move all joints during specific therapies, where it has been shown that training involving several joints simultaneously generates a greater physiological condition [ 47 ]. This indicates that, by assisting more joints, the performance of the two devices improves by reducing the activity of most of the muscles evaluated, which means complete assistance to the hip and knee flexion/extension movements allowing a passive degree of hip adduction/abduction and, in addition, providing dorsi-plantarflexion of the ankle with a soft mechanism that permits greater degrees of freedom in this joint.…”

A Novel Variable Stiffness Compound Extensor-Pneumatic Artificial Muscle (CE-PAM): Design and Mathematical Model

“…The Bridgestone Company produced the first commercial version of the pneumatic artificial muscle (PAM) [2]. It is used to construct soft robots with several bendable joints and a high degree of freedom, rather than rigid robots with discrete fixed joints [3][4][5][6][7]. These robots provide safer interactions with humans when directly in contact with their bodies [8][9][10][11][12].…”