Design and implementation of a stumble recovery controller for a knee exoskeleton

Abstract

This paper presents a stumble recovery controller for a knee exoskeleton that detects a stumble perturbation; selects an anticipated recovery strategy; and provides appropriate recovery assistance. In order to assess the efficacy of the controller in providing an assistive response to a stumble perturbation, the controller was implemented in a knee exoskeleton and evaluated in a single healthy adult participant against several other controller reactions, and against the participant’s response without an exoskeleton. Results show that the stumble recovery controller successfully detected the perturbation and correctly selected the strategy that matched the participant’s response for all 29 trials in which the exoskeleton was used. Further, results show improvements in stumble recovery metrics when using the exoskeleton with the stumble recovery controller, compared to the control cases of: 1) no change in the nominal controller when stumble is detected; 2) turning off exoskeleton torque when a stumble is detected; and 3) not wearing an exoskeleton.