Design and Evaluation of Lightweight Adaptive Flexible Ankle Rehabilitation Robot

To solve the problem of gait instability or falling during the walking process for stroke survivors, a new flexible ankle rehabilitation robot (FARR) was designed to improve abnormal gait that caused by the foot drop due to insufficient ankle dorsiflexion (DF) and insufficient propulsion as a result of insufficient ankle plantarflexion (PF). First of all, in view of the impact that the rigid ankle joint robot increases the metabolism and psychological discomfort of stroke survivors, the FARR transmitted mechanical power generated by an actuator to a wearer through the interaction of functional textiles and Bowden cable (BC) transmissions and its features are lightweight and concealed. Furthermore, the single-motor bidirectional drive mode was adopted to reduce the mass and volume of the actuator. A lightweight tension sensor which is embedded in the shoe cover was developed to realize real-time detection of auxiliary force. Then, the hierarchical control was adopted to make that the FARR can be used for wearers with different body types and gaits. The high-level controller included gait movement intention recognition and BC trajectory generation algorithm based on gait events, which is used to realize adaptive adjustment of control parameters and improve system robustness. The low-level controller refers to the BC trajectory to assist ankle joint PF and DF. Finally, the experimental platform was built to test the auxiliary effect of the FARR. When the FARR provided assistance, the PF angle and ground propulsion of the subject increased at the terminal stance, and the DF angle of the subject also increased during the swing phase. Moreover, when the FARR did not provide power assistance, the PF passive force provided PF assistance to enhance ground propulsion of the subject at the terminal stance. The results show that the FARR is a promising ankle rehabilitation device that has the effect of improving the ground propulsion and plantar clearance for stroke survivors. © 2022 Editorial Office of Chinese Journal of Mechanical Engineering. All rights reserved.