Research On Electro-hydraulic Servo Control System Of Standing-up Lower Limb Exoskeleton

Lower limb exoskeleton can mimic the exoskeleton in the biological world and is a highly automated electromechanical(liquid and pneumatic)device.In medical field,lower limb exoskeleton is mainly used in rehabilitation to assist in restoration of basic lower limb function in patients with lower limb motor dysfunction.The first task in the basic rehabilitation of lower limb motor function is to help patients who can only stand in a sitting position to do so.By analysing the current status and shortcomings of lower limb exoskeleton at home and abroad,a standing-up lower limb exoskeleton is designed.This research takes the standing-up lower limb exoskeleton as the research object.And it conducts in-depth research on the mechanical structure,working principle,motion modelling,hydraulic drive system function and electro-hydraulic servo system performance.The design of a rational control system is combined with the functional requirements of the standing-up lower limb exoskeleton and its electro-hydraulic servo system.And a AMESim/Simulink simulation is carried out to ensure the reliability of the standing-up lower limb exoskeleton.The following are the main contents of the study.Firstly,this dissertation analyzes human standing-up process,and studies the motion form,basic structure and range of joint rotation angle of the human lower limb joints.The mechanical structure of the standing-up lower limb exoskeleton is designed by specifying its working requirements.And the relationship between the rotation angle of hip and knee joints and the output displacement of the hydraulic drive system is derived.Then,kinematics and dynamics of the standing-up lower limb exoskeleton are analyzed and driving torques of each joint during the standing-up process are obtained by using ADAMS software.Secondly,considering the overall light weight and strong working stability of the standing-up lower limb exoskeleton,this dissertation selects the hydraulically drive.And the design of hydraulic drive system is completed and the working principle is clarified.Then,the core components of hydraulic drive system,such as hydraulic oscillating cylinder,hydraulic linear cylinder,hydraulic pump and electro-hydraulic servo valve,are designed and selected.Again,electro-hydraulic position servo system of the standing-up lower limb exoskeleton is used as the object.And a mathematical model is established for each link to obtain the transfer function of electro-hydraulic position servo system.The dynamic characteristics of the system are also studied and analyzed,and a reasonable control system is designed.Finally,in order to study the following effect of the standing-up lower limb exoskeleton,classical PID control,fuzzy PID control and genetic-fuzzy PID control are designed.Through simulation studies in Simulink,fuzzy PID control for hip joint and genetic-fuzzy PID control for knee joint in standing-up lower limb exoskeleton are determined.Through AMESim/Simulink simulation of electro-hydraulic position servo system,the rationality of the control system is verified.And the control system meets the design requirements and effectively improves the position control accuracy and following capability of the standing-up lower limb exoskeleton.