Lower-limb Exoskeleton Based on Variable Stiffness Drive

Aiming at the problems that the traditional rigid-driven exoskeleton is not compliant enough in complex humanrobot interaction environment and cannot guarantee the safety of the human body, a variable stiffness lower-limb exoskeleton is designed for rehabilitation training. A reconfigurable variable stiffness principle is proposed, which realizes the change of joint stiffness by adjusting the preload of the joint spring, and increases the stiffness adjustment range of the exoskeleton through reconfiguration of the pulley block. A variable stiffness actuator for driving the active joints of the exoskeleton is designed based on the proposed reconfigurable variable stiffness principle, and the mechanical structure of the variable stiffness lower-limb exoskeleton is further designed. The theoretical stiffness model of the exoskeleton is established, and its stiffness characteristics are analyzed by simulation. The experimental platform of variable stiffness lower-limb exoskeleton is built, and the stiffness characteristics of the prototype are tested and verified. The results show that the stiffness curve of the experiment coincides with the theoretical model. Based on the torque-deflection angle characteristics of variable stiffness drive, a control method for walk following by the exoskeleton without interactive force sensor is proposed, and corresponding experiments are carried out at different speeds. The test results show that the maximum interaction torque between the exoskeleton and the human body is 0.8243 N·m, which proves that the exoskeleton can follow the movement of the human body.