Research On Control System Of Lower Limb Assisted Exercise Device

The lower limb assisted exercise device is a portable wearable smart device that ingeniously combines the human lower limb with the machine structure,can provide support and protection for the human body,and can also assist the human body to complete walking and other behaviors.According to different functions,it can be divided into: rehabilitation type auxiliary exercise devices dedicated to solving the movement problems of patients with lower extremity loss or severe injury and auxiliary exercise equipment that enhances the load capacity of the human body.This paper focuses on the research of the control system of lower limb auxiliary motion device,and the following work is mainly done:(1)Through reading the literature,summarize the research background,purpose and significance of the lower extremity auxiliary exercise device,summarize the structure and control method of the lower extremity auxiliary exercise device at home and abroad,and look forward to the development trend of the lower extremity auxiliary exercise device.(2)Combined with the knowledge of human anatomy,the physiological structure of human lower limb joints was analyzed to study the movement mechanism of each joint of the lower limb.Analyze the human movement gait rule and divide gait cycle.The motion state curve of lower limb joints is drawn by Open Sim software,the joint motion angle is derived,and the joint motion function is fitted,which provides a theoretical basis for joint tracking.According to the principles of comfort,safety and adaptability of lower limb auxiliary motion device,the structural design of lower limb auxiliary motion device is carried out.(3)Combined with coordinate transformation,the D-H model of the lower limb auxiliary motion device is established.The kinematics and dynamics model of the lower limb auxiliary motion device is established by using the kinematics and dynamics theory of the robot.The Lagrange method is used to solve the dynamic parameters of the lower limb joints of the human body,which provides a reference model for the study of joint control algorithm.(4)Different control algorithms of human auxiliary motion device are analyzed,and the advantages and disadvantages of traditional PID control,robust control,adaptive control and fuzzy control are compared.The friction in the motion process of human auxiliary motion device is adaptively compensated by the approximation characteristics of fuzzy control.In the design of the controller,the approximation of the fuzzy system will cause systematic errors.Robust control is added to eliminate the approximation error and improve the stability of the system.(5)It is difficult to establish an accurate mathematical model because of the uncertainty and time-variability of the auxiliary motion device system model.A model-free adaptive iterative learning control algorithm is proposed,which is similar to data-driven theory.The implementation process of this algorithm is based on the model-free adaptive method to transform and linearize the dynamic performance equation of the lower limb auxiliary exercise device system,and design the controller to combine the optimal method and introduce it.The estimated value of the parameter can iteratively adjust the system parameter according to the output error information to realize the tracking of the joint trajectory.