Design And Dynamic Characteristics Of Prosthesis Knee Joint Based On Magnetorheological Damper

With frequent traffic accidents and natural disasters,the number of amputees has risen sharply.At present,medical technology can not regenerate limbs,prosthetics become the only effective way to help amputees recover their walking function.Prosthesis knee joint is the most important functional part of lower limb prosthesis.Relative to the pneumatic or hydraulic prosthetic knees,the prosthetic knees based on magnetorheological(MR)effect have become one of the focus directions as the intelligent prostheses,as they have several obvious advantages such as fast response,controllable damping force,and low power consumption.However,the existing prosthetic knee joints mostly use uniaxial structure and the dampers are industrial products,which makes it impossible to guarantee the quality and comfort of human gait during movement.Therefore,it is of great academic significance and practical value to develop a prosthetic knee joint with good gait and strong self-adaptive ability.In this paper,according to the characteristics of human gait in the process of movement,a set of motion detection device for lower limb joints is designed.By collecting the lower limb motion information,the flexion angles of each joint under different gait conditions are obtained.The gait analysis is based on five most common types of gait,which included walking on flat ground,walking up and down stairs,and walking up and down slopes.By processing the collected data,the movement stick diagram of the joint and the gait cycle diagram are drawn.At the same time,the movement law of the lower limb prosthesis is also analyzed for the design and control of prosthetic knee joint.According to the research on the instantaneous center trajectory and the stability of the knee joint,the double-rocker is selected as the motion mechanism of the knee joint,and the configuration and size of the double rocker mechanism are determined.At the same time,with the optimization goal of small size and low energy consumption,the optimum size of MR damper is obtained.An experimental study on the optimized MR damper is conducted to verify the optimization results.The double-rocker structure and the MR damper are integrated to achieve the design goal of the prosthetic knee joint.In order to achieve accurate analysis and control of the double-rocker prosthesis knee joint,kinematics and dynamics analysis are carried out.A simplified model of the lower limb prosthesis including thighs and lower legs is constructed,then the kinematic parameters of each key point of the lower limb prosthesis are obtained;Based on the Lagrange equation and D'Alembert principle,the dynamic analysis model of prosthetic knee joint is established,and the relationship between the damping force and the driving torque of the knee joint is established,which lays the foundation for the simulation and control of the double-rocker prosthesisknee joint.According to the movement of human lower limbs and kinematics dynamics analysisresults,combine with the simulation software ADAMS,the simulation analysis of five common gait of prosthetic knee joint is realized.The motion law of the prosthetic knee joint and the working condition of the MR damper are obtained,and the rationality of the prosthetic knee joint design is verified through comparative analysis.