Assistive Control of Knee Exoskeletons for Human Walking on Granular Terrains

2024-11-18

arXiv.org

AI Summary

To address abnormal gait patterns and elevated metabolic cost during locomotion on granular terrain (e.g., sand), this paper proposes a stiffness-parameterized model predictive control (MPC) framework for knee exoskeletons, integrating real-time ground reaction force (GRF) estimation via machine learning and joint torque feedback to enable adaptive assistance. Key contributions include: (i) the first lightweight, real-time GRF estimation algorithm specifically designed for granular terrain; and (ii) a stiffness-parameterized MPC controller that jointly optimizes muscle activation and metabolic rate. Indoor and outdoor experiments demonstrate that, during over-sand walking, the approach reduces primary lower-limb muscle activation by 15% and net metabolic cost by 3.7%, confirming its effectiveness and practicality on complex, unstructured terrains.

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• Humans and AI: Human-Aware Planning and Behavior Prediction

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Abstract

Human walkers traverse diverse environments and demonstrate different gait locomotion and energy cost on granular terrains compared to solid ground. We present a stiffness-based model predictive control approach of knee exoskeleton assistance on sand. The gait and locomotion comparison is first discussed for human walkers on sand and solid ground. A machine learning-based estimation scheme is then presented to predict the ground reaction forces (GRFs) for human walkers on different terrains in real time. Built on the estimated GRFs and human joint torques, a knee exoskeleton controller is designed to provide assistive torque through a model predictive stiffness control scheme. We conduct indoor and outdoor experiments to validate the modeling and control design and their performance. The experiments demonstrate the major muscle activation and metabolic reductions by respectively 15% and 3.7% under the assistive exoskeleton control of human walking on sand.

Problem

• Control knee exoskeletons on granular terrains
• Predict ground reaction forces using machine learning
• Reduce muscle activation and metabolic cost

Innovation

• Stiffness-based model predictive control
• Machine learning for GRF estimation
• Exoskeleton reduces muscle activation