A Disturbance-Cancelling Approach for Ankle Exoskeleton Assistance Improves Standing Balance Performance and Reduces Human Effort

Though lower-limb exoskeletons show promise as mobility aids, their lack of proper balance control hinders user safety and real-world use. Previous balance controllers have been based on deviations in center of mass velocity, which require knowledge of desired motions (user intent). Here we propose a new balance controller that directly counteracts an estimated disturbance while taking into account user action. To assess this new disturbance-cancelling approach, we implement this controller in ankle exoskeletons and test with three healthy adults during standing forward pushes. With assistance, participant responses substantially improved in performance and effort, as evidenced by a 50% reduction in recovery steps taken, 32% reduction in anterior center of mass displacement, and 16% reduction in biological torque vs. no assistance. This proof of concept offers a promising approach to addressing balance control in lower-limb exoskeletons, which could ultimately help reduce fall risk for mobility-impaired populations.