Design And Control Algorithm Development Of The Knee Exoskeleton

An exoskeleton is a wearable device that provides improved functionality to the human for various tasks,such as rehabilitation therapy,enabling individuals to carry heavy loads,and assisting the disabled and the elderly.As the applications of carrying heavy loads,the exoskeleton can enhance the wearer's body ability and reduce energy consumption.It can be used as a long-range walking assist device for military purposes,too.As function of the auxiliary rehabilitation therapy,the exoskeleton can help the disabled and the elderly for walking and take some loads.The exoskeleton device in this study aims to help elderly or medical rehabilitation in the open air.Because of lower limbs exoskeleton heavy,this study focuses on single limb exoskeletons.The knee exoskeleton has been studied by foreign research institutes,and is still in the theoretical stage in China.It is concluded that the knee joint exoskeleton abroad is more cumbersome or expensive to develop,so this research has designed and manufactured this lightweight knee exoskeleton device.This article will introduce the following aspects:1.Mechanical structure.The structure of the new knee exoskeleton equipment mainly includes:Mechanical body and hydraulic damper.The rotation of the knee is driven by a hydraulic damper.In order to meet the wear requirements and light weight,the two editions of exoskeleton mechanical body and damper were designed and manufactured.As the main component of the exoskeleton-hydraulic damper,ADAMS software was used for simulation analysis,as well as kinematics and dynamics analysis.Finally,the appropriate parameters of the dampers were selected.2.Control system.The control chip use STM32,the hardware structure of signal acquisition is made.By collecting a set of plantar pressure signals and a knee angle signal,judging the current posture of the human body,according to different attitude,the damper oil port is controlled.Finally,the damping force of the knee joint is adjusted.3.Algorithm development.On the basis of the mechanical structure,the backstepping control algorithm is developed to control knee angle.The gait characteristics of the wearer can be closer to the standard gait.In order to verify the effect of its algorithm,the backstepping control,fuzzy PID algorithm and PID are compared.It is found that the backstepping control algorithn has better tracking effect under step and sinusoidal signals.Secondly,the joint simulation of MATLAB and ADAMS software is carried out,and the simulation results show that the backstepping control algorithm has a better auxiliary effect in this knee joint exoskeleton system.4.In order to test the exoskeleton device,the wearable test and walking test were carried out.After wearing,it is comfortable.It can satisfy the knee angle requirements of different posture such as up and down stairs,sitting and walking on the ground.Then,the exoskeleton was worn,the knee angle between the encoder and the standard is compared,it is proved that the control logic has a good effect.