Walking Strategies and Performance Evaluation for Human-Exoskeleton Systems under Admittance Control

Area of Science:

• Robotics
• Biomechanics
• Assistive Technology

Background:

• Lower-limb exoskeletons are advanced assistive devices requiring precise intention detection and performance evaluation.
• Previous research established disturbance observer (DOB)-based torque estimation and admittance control for human-exoskeleton systems (HES), validated without ground reaction force (GRF).

Purpose of the Study:

• To integrate a sensing and communication module for measuring and compensating GRF in an exoskeleton control system.
• To analyze the robust stability of the closed-loop system with GRF compensation.
• To evaluate the performance of the admittance control law with GRF compensation using novel indices.

Main Methods:

• Integration of foot-mounted sensing and communication modules to measure and compensate for GRF.
• Theoretical analysis to derive conditions for robust stability of the closed-loop human-exoskeleton system.
• Experimental validation on level ground with multiple subjects and parameter combinations, evaluating performance using normalized energy consumption index (NECI) and walking distance.

Main Results:

• The proposed system successfully measures and compensates for GRF, enhancing exoskeleton control.
• Rigorous analysis confirmed the robust stability of the closed-loop system under the new conditions.
• Experimental results demonstrated that the admittance control law significantly reduces user energy consumption during level ground walking.

Conclusions:

• The developed GRF measurement and compensation system is effective for lower-limb exoskeleton control.
• The proposed admittance control law improves walking efficiency by reducing user energy expenditure.
• This research advances the development of more effective and user-friendly walking assistive devices.