Human-Robot Interactive Control for Knee Exoskeleton Using Feedback Torque and Adjustable Stiffness

Aiming at the problem that the rigid exoskeleton has insufficient compliance due to mechanical vibration in the human-robot cooperation motion and can only move within a small range of designed trajectories, the user's active motion intention cannot be fully expressed. In this paper, a human-robot cooperation control method using compliance factor with feedback torque and adjustable stiffness is proposed, which can arbitrarily change the current motion trajectory according to the user's active intention torque, while the knee exoskeleton can maintain the compliance and stability of the motion. The compliance factor includes stiffness adjustment items and torque adjustment items. The stiffness change feedback based on SEA improves the flexibility. The intention amplification function is designed to enhance the user's active intention. The proposed method is validated by the designed knee exoskeleton. When feedback compliance factor, knee exoskeleton has good compliance and flexibility. In extension and flexion, the highest γ values (γ reflects the intensity of the subject's initiative) are 3.390 and 3.705., respectively.