Adaptive Negative Damping Control for User-Dependent Multi-Terrain Walking Assistance With a Hip Exoskeleton

Area of Science:

• Robotics
• Biomechanics
• Human-Machine Interaction

Background:

• Current hip exoskeletons struggle with personalized assistance and environmental adaptation.
• Existing control strategies often fail to accommodate individual gait patterns and diverse terrains.

Purpose of the Study:

• To develop a novel adaptive control strategy for hip exoskeletons that adjusts mechanical impedance.
• To create a controller that injects energy while allowing user control and voluntary contribution.
• To enable seamless adaptation to multi-terrain environments using Bayesian Optimization.

Main Methods:

• Designed hip assistive torques as adaptive virtual negative damping.
• Implemented Bayesian Optimization for adaptive assistance strength tuning.
• Conducted experiments with five healthy subjects to evaluate the controller.

Main Results:

• Achieved an average reduction of 7.2% in metabolic cost of walking compared to free walking.
• Preserved lower-limb kinematics and ensured synchronized user-exoskeleton action.
• Demonstrated minimal exoskeleton power losses (<2%) and efficient power transmission across terrains.

Conclusions:

• The novel controller offers individualized, adaptable, and straightforward assistance for hip exoskeletons.
• The strategy advances the development of user-dependent control laws for enhanced mobility.
• The adaptive impedance control strategy proves effective for energy-efficient and adaptable exoskeleton assistance.