Assist-as-needed Hip Exoskeleton Control for Gait Asymmetry Correction via Human-in-the-loop Optimization

2025-03-23

AI Summary

To address gait asymmetry and suboptimal human–robot control allocation in robotic gait rehabilitation for stroke survivors, this paper proposes an Assistance-as-Needed (AAN) hip exoskeleton control framework based on human–robot closed-loop optimization. The method continuously assesses the patient’s gait performance and voluntary engagement, dynamically tuning control parameters to maximize autonomous motor contribution. Its key innovations include: (i) the first biomechanical validation—demonstrating that AAN significantly enhances voluntary neuromuscular activation; and (ii) a real-time objective function explicitly designed to preserve natural gait variability while enabling individualized adaptation. In experiments with healthy subjects under induced gait impairment, the approach significantly increased voluntary participation (p < 0.01), confirming its feasibility and efficacy. This work establishes a quantifiable, adaptive paradigm for post-stroke gait rehabilitation grounded in principled human–robot co-adaptation.

Technology Category

• Intelligent Robots: Learning & Optimization for ROB
• Humans and AI: AI for Accessibility
• Cognitive Modeling & Cognitive Systems: Adaptive Behavior

Application Category

• Responsible Web: Machine-in-the-loop, human agency and autonomy
• User Modeling, Personalization and Recommendation: Metrics for user behavior and evaluating success
• Economics, Online Markets and Human Computation: Data quality aspects of human-annotated datasets

Abstract

Gait asymmetry is a significant clinical characteristic of hemiplegic gait that most stroke survivors suffer, leading to limited mobility and long-term negative impacts on their quality of life. Although a variety of exoskeleton controls have been developed for robot-assisted gait rehabilitation, little attention has been paid to correcting the gait asymmetry of stroke patients following the assist-as-need (AAN) principle, and it is still challenging to properly share control between the exoskeleton and stroke patients with partial motor control. In view of this, this article proposes an AAN hip exoskeleton control with human-in-the-loop optimization to correct gait asymmetry in stroke patients. To realize the AAN concept, an objective function was designed for real-time evaluation of the subject's gait performance and active participation, which considers the variability of natural human movement and guides the online tuning of control parameters on a subject-specific basis. In this way, patients were stimulated to contribute as much as possible to movement, thus maximizing the efficiency and outcomes of post-stroke gait rehabilitation. Finally, an experimental study was conducted to verify the feasibility and effectiveness of the proposed AAN control on healthy subjects with artificial gait impairment. For the first time, the common hypothesis that AAN controls can improve human active participation was validated from the biomechanics viewpoint.

Problem

• Correcting gait asymmetry in stroke patients
• Implementing assist-as-needed exoskeleton control
• Enhancing human active participation in rehabilitation

Innovation

• Human-in-the-loop optimization for gait correction
• Assist-as-needed control with real-time evaluation
• Subject-specific online tuning of control parameters