Study On Motion Analysis And Joint Control Of Lower Extremity Exoskeleton

As the population ages and accidents occur,the number of people with lower limb motor dysfunction is increasing,and their quality of life cannot be guaranteed due to their mobility inconvenience.The situation faced by this group of people is an urgent problem to be solved in China.The research and development of lower extremity exoskeleton robot provides a new idea to solve the above problems.This paper designs a lower extremity exoskeleton robot,which mainly realizes two functions: one is to help patients with lower extremity motor dysfunction to carry out rehabilitation training,so that they can recover their walking ability;the second is to provide power and endurance for the wearer and reduce their own energy consumption.According to the above requirements,based on the lower extremity exoskeleton structure designed in this paper,the motion analysis and joint control and other aspects of the study were carried out to build the exoskeleton single joint experimental platform for impedance control experiment.The main work of this paper is as follows:(1)By analyzing the physiological structure and movement characteristics of the human leg joints,the design requirements and basic components of the lower limb exoskeleton were summarized,and the appropriate degree of freedom was selected according to the walking correlation degree.Then the specific structure of each joint is introduced in detail.The innovation of this paper is mainly reflected in the improvement of the structure of the knee joint.According to the movement characteristics of human lower limbs,the knee joint is designed as a four-link structure with high bionic degree,and the appropriate driving mode is selected on this basis.Finally,the structural model of each part is established in Solid Works and assembled into the overall model of the lower limb exoskeleton.(2)The mathematical concepts related to the robot are described.According to the above mechanical structure,the DH model is established to solve the motion equation.The kinematics constraints of knee joint were analyzed.In addition,the method of special joint Angle is used to verify the correctness of the kinematics solution by using the geometric structure characteristics of the exoskeleton.(3)The control method and process of the single joint of the lower extremity exoskeleton are analyzed,and the PID control algorithm is emphatic introduced.Secondly,the dynamic form of the exoskeleton is analyzed,the basic model of the servo motor is established,the single joint of the exoskeleton is compensated by gravity,and the PD controller based on gravity compensation is established.Finally,a single joint experimental platform was built and gravity compensation experiment was carried out to verify the rationality of PD controller.(4)The modeling and control methods of the single joint of the exoskeleton are analyzed,with emphasis on the PID control algorithm.Secondly,the basic model of the servo motor was established,and the position control and simulation were carried out for the passive control of the exoskeleton single joint.Thirdly,dynamic analysis is carried out,and impedance control is studied for active control.Finally,the exoskeleton single joint experimental platform was built to conduct the impedance control experiment.