Knee Flexion-Assisted Method for Human-Exoskeleton System

Area of Science:

• Biomechanics
• Robotics
• Human-Machine Interaction

Background:

• The knee joint is a key focus for lower extremity exoskeleton research.
• The effectiveness of contractile element (CE)-based flexion assistance throughout the entire gait cycle remains unclear.

Purpose of the Study:

• To analyze effective knee flexion assistance methods using passive element (PE) energy mechanisms.
• To design an enhanced adaptive oscillator (EAO) for seamless human-exoskeleton integration.
• To validate the necessity of specific assistance profiles for CE-based knee flexion support.

Main Methods:

• Analysis of PE energy storage and release for optimal assistance timing.
• Development of an EAO incorporating fundamental frequency estimation via discrete Fourier transform (DFT) and a finite state machine (FSM).
• Experimental validation using electromyography (EMG) and metabolic indicators to assess assistance effectiveness.

Main Results:

• CE-based knee flexion assistance is most effective when aligned with the entire joint power period, not solely the negative power phase.
• Ensuring human active movement during assistance significantly reduces antagonistic muscle activation.
• The proposed EAO with DFT and FSM enhances system stability and practicality.

Conclusions:

• Effective CE-based knee flexion assistance requires synchronization with the full joint power cycle and support for active human movement.
• The EAO provides a robust method for integrating human intent with exoskeleton assistance.
• Findings inform the design of more natural and efficient lower extremity assistive devices.