Design And Research Of Adaptive Variable Instantaneous Rotation Center Artificial Knee Joint

With the acceleration of China ’s aging process and the frequent occurrence of various accidents,the number of people who lose their mobility has increased year by year.As an important part of lower limb prosthesis,the performance of artificial knee joint will affect the rehabilitation and daily travel of users.Aiming at the problems of the existing artificial knee joint in theory and practical application,such as the inconsistency between the instantaneous rotation center(instantaneous center)and the instantaneous center motion trajectory of the human knee joint,the inability to adjust adaptively according to different users,and the poor flexibility of the driving source,this thesis designs an adaptive variable instantaneous center artificial knee joint driven by pneumatic artificial muscle.The joint introduces additional degrees of freedom on the basis of the ordinary inverse quadrilateral artificial knee joint to indirectly change the rod length of the inverse quadrilateral structure,so as to adjust the instantaneous center position of the original artificial knee joint,improve the bionic performance and adaptive ability of the artificial knee joint,and improve the flexibility of the artificial knee joint as the driving source.The main contents of this thesis are as follows :(1)Adaptive variable instantaneous center artificial knee joint structure design.By analyzing the motion characteristics of the human knee joint during normal motion,the design goal of the adaptive variable instantaneous center artificial knee joint is clarified,and the driving mode of the artificial knee joint is selected.Finally,the overall design scheme of the artificial knee joint is proposed,and the instantaneous center motion trajectory equation of the artificial knee joint is established.(2)Adaptive variable instantaneous center artificial knee joint optimization design.Firstly,the size of four different types of ordinary anti-quadrilateral artificial knee joints is optimized,and the instantaneous center trajectory is analyzed.The optimized instantaneous center trajectory is compared with the ideal instantaneous center trajectory of the human knee joint.The analysis results show that the ordinary anti-quadrilateral artificial knee joint still has deficiencies in bionic performance.Then,based on the optimization results of the ordinary inverse quadrilateral artificial knee joint,the optimization of the adaptive variable instantaneous center artificial knee joint is completed.The adaptive adjustment curve of the artificial knee joint is obtained when the ideal instantaneous center motion trajectory of the human knee joint is obtained,and the instantaneous center motion trajectory of the artificial knee joint is analyzed.The analysis results show that the proposed adaptive variable instantaneous center artificial knee joint has better bionic performance and adaptive ability.(3)Research on kinematics and dynamics of adaptive variable instantaneous center artificial knee joint.The kinematics analysis of the proposed adaptive variable instantaneous center artificial knee joint is carried out,and the kinematics equation of the artificial knee joint is established.The correctness of the kinematics equation is verified by simulation.At the same time,it is proved that the artificial knee joint can meet the normal knee flexion range of the human body,and its instantaneous center motion trajectory conforms to the instantaneous center motion trajectory of the human knee joint.Based on the kinematics equation,the Lagrange method is used to establish the dynamic equation of the artificial knee joint,and the relationship between the generalized coordinates and the generalized force is obtained.The three-dimensional model of the artificial knee joint is established by three-dimensional simulation software,and the dynamic simulation is carried out.The simulation results verify the correctness of the dynamic equation.(4)Research on control strategy of adaptive variable instantaneous center artificial knee joint.According to the dynamic equation of the artificial knee joint,the fuzzy PID controller for the artificial knee joint control is designed,and the control loop of the whole artificial knee joint system is designed.The control effect of the ordinary PID controller and the fuzzy PID controller is compared by simulation.The comparison results show that the fuzzy PID controller is superior to the ordinary PID controller.Based on the designed fuzzy PID controller,the tracking control simulation of the instantaneous center motion trajectory of the artificial knee joint is carried out.The simulation results verify the effectiveness of the control system.(5)Experimental study of adaptive variable instantaneous center artificial knee joint prototype.According to the proposed adaptive variable instantaneous center artificial knee joint structure,the related parts are processed and the prototype experimental platform is built.The motion tracking control experiment is carried out by the fuzzy PID controller written by Labview.The experimental results show that the adaptive variable instantaneous center artificial knee joint designed in this thesis has good bionic and adaptive ability,and can track the ideal instantaneous center trajectory well under the control of fuzzy PID controller,which meets the design requirements.