Control System Design And Comfort Study Of Lower Limb Power-assisted Exoskeleton

The main functions of the exoskeleton include enhanci ng the endurance and explosive power of the human body,assisting patient movement,supporting and protecting users,etc.It is an intelligent machin e that combines the ability of the human brain to judge and the power of mechanical systems.Exoskeleton is a popular research field in engineering in recent years.Foreign research institutions have developed a variety of exoskeleton products used in milit ary,medical rehabilitation,fire fighting,industrial production and other different fields.The United States,Japan,Switzerland lead the way in exoskeleton development,and some products have entered the market and achieved good achievements.However,most of the domestic exoskeleton research and development are in the prototype production stage,and there is still a long way to go before it is actually applied.There are still some problems to be solved in the exoskeleton research and development p rocess,for example,the control is not precise enough,the human-machine interaction is not friendly enough,the cost is too high to be applied on a l arge scale,and energy supply is not sustainable.The purpose of this article is to design a lower extremity assisted exoskeleton to help the elderly or patients with mobility problems to travel,expand their range of activities.This exoskeleton has a simple structure and precise control,which can effectively improve the user’s quality of life.The main work of this article is as follows:(1)The design ideas and design principles of lower extremit y assisted exoskeleton were determined.Based on the posi tioning of this exoskeleton,the overall layout plan is completed,including designing the mechanical structure,selecting the driving method and control method.(2)Based on the modified D-H method,the kinematic model of the exoskeleton lower limb mechanical leg is constructed and the forward and inverse solutions of the exoskeleton kinematics are solved.The exoskeleton velocity analysis is performed by solving the Jacobian matrix.The exoskeleton motion simulation was performed to complete the gait planning and obtain the gait parameters.(3)The Lagrange functional balance method is used to analyze the dynamics of the lower extremity assisted exoskel eton,and the relationship between the joint driving torque and the movement status of the mechanical leg is obtained.The fuzzy-PID dual-mode control is used as the control algorithm of exosk eleton joints,and a control model is constructed.Through joint simulation,it is verified that in the design of exoskeleton control system,fuzzy-PID dual-mode control is better than classic PID control.(4)The evaluation of comfort based on ergonomics is analyzed,especially the objective evaluation criteria of body pressure distribution for seat comfort.An objective evaluation index of exoskeleton comfort based on human-machine motion deviation is proposed,and a dynamic simulation analysis of the hu man-machine system is performed to verify the rationality of the evaluation method.