Prediction of expected Angle of knee joint of human lower limbs based on leg interaction

Abstract

In order to convert the leg interaction force between the exoskeleton and human body into the expected angle of the movement of the human hip and knee at the next moment, and realize the recognition of human motion intention, the mapping relationship between the joint angular velocity and the active joint torque generated by the leg interaction force was studied. Firstly, by collecting joint angle data from the gait experiment, the movement characteristics of lower limb swing phase and support phase in normal daily gait were analyzed, and the joint angle prediction strategies for different phases of human body were determined. Then, by establishing the dynamic model of exoskeleton under human-machine coupling, the formula of human body gravity compensation was obtained. Then, regarding the leg swing phase, the nonlinear mapping relationship between the joint angular velocity of human body and the joint torque generated by the interaction force of the leg after gravity compensation was established through the admittance control model. The desired Angle was obtained by multiplying the angular velocity of the control period plus the current joint angle. Finally, for the prediction of the expected joint Angle of the leg support phase, the hip joint should be controlled by position to keep the back of the exoskeleton upright, and the knee joint should adopt the same algorithm as the swing to obtain the desired joint angle.