Study On Nonlinear Dynamics Of Bionic Artificial Knee Joint Motion

The knee joint is the largest and most complex joint in the human body,which plays an indispensable role in People’s Daily work and life.At the same time,the knee joint is also very fragile,and the injury of the knee joint is a very common orthopedic disease,so the research on the knee joint is particularly important.Due to the particularity of the structure and function of the knee joint,people can not use in vitro or static test to separate the knee joint from other human structures,and it is difficult to quantitatively analyze the movement of each part of the knee joint.Therefore,a bionic artificial prosthetic leg knee joint model is established.It is an effective means to deepen the understanding of knee joint through numerical simulation to analyze the dynamic behavior of knee joint motion.From the perspective of nonlinear dynamics,the knee joint system is simplified into a collision and vibration system model based on the knee joint structure and activity characteristics,in which the femur,tibia and patella are expressed as mass with different qualities in turn,and the interarticular ligament,tendon,meniscus and other structures have a certain ability to cushion and absorb vibration.Based on this,a two-degree-of-freedom or three-degree-of-freedom collision and vibration system model with gap-elastic(rigid)constraint was established to simulate the collision,vibration or friction behavior among femur,tibia and patella in the process of vertical stress of human lower limbs.In this paper,on the basis of modeling,using the fourth-order Runge-Kutta numerical integration method,combined with bifurcation diagram,phase trajectory diagram,time history diagram and Poincaré section diagram,the nonlinear motion law of the knee joint system under the condition of low frequency has been discussed,besides,discussing the effect of the damping parameters,stiffness parameters,load,etc.on the system’s impact and vibration characteristics.Preliminary studies have shown that a healthy knee joint system undergoes steady-state motion at low frequencies without the occurrence of quasi periodic or chaotic motion.However,in the case of ligament or tendon injury,the knee joint system undergoes multi periodic motion and the number of collisions between joints significantly increases.When the meniscus or articular cartilage is damaged,the dynamic behavior of the system is very complex,exhibiting multi periodic and chaotic motion,making it difficult for the knee joint system to operate normally.The changes in knee joint load also have a significant impact on its dynamic behavior.The larger the load,the more susceptible the knee joint is to injury or even destruction.Adjusting the stiffness and damping parameters of knee joint motion can reduce the vibration amplitude between joints.A healthy knee joint and patella are crucial and indispensable for the knee joint system.After knee joint injury,it is necessary to reduce the frequency and amplitude of joint movement,try to keep it stationary or work in an appropriate frequency band,otherwise it will exacerbate friction and collision behavior between joints,which is not conducive to the recovery of knee joint injury.By analyzing the effects of different parameters on system dynamics response,this provides a certain reference for the maintenance of human knee joints and a theoretical basis for the optimization design of future biomimetic artificial legs.