Research On Lower-limb Exoskeleton Based On Passive Dynamic Walking Theory

In recent years,as the number of patients with lower limb motor dysfunction caused by factors such as population aging,diseases,disasters and accidents has been increasing year by year,relevant medical resources have become increasingly tense.Lower limb exoskeleton,as a kind of walking/rehabilitation robot worn on the outer side of the lower limbs of the human body,aims to help people with mobility impairments and improve their living conditions,while effectively coping with the increasingly tense predicament of medical resources and alleviating the increasingly serious aging of the population.The issue of chemistry is of great significance.In addition,lower extremity exoskeleton also has broad application prospects in the fields of transportation,rescue and rescue,marching operations,scientific expeditions and so on.As an interdisciplinary technology,domestic and foreign researchers have achieved many results in exoskeleton theory demonstration and prototype development,but they still exist in the lightweight design of exoskeleton structure,battery life,human-machine coordination,and evaluation of assistance effects.More research difficulties limit the engineering application of exoskeleton.Based on previous research results,this research discusses the design of exoskeleton from the perspective of passive dynamic walking theory,proposes the concept of active and unpowered exoskeleton design,and develops two prototypes of lower extremity exoskeleton,aiming to reduce human walking energy consumption.The main research contents are as follows:(1)Based on the analysis of the structure and biomechanics of the lower limbs of the human body,the characteristics of the joint motion of the lower limbs of the human body and the periodic characteristics of the walking gait of the human body are elaborated.Analyze the movement characteristics of the lower limbs in the swing phase and the support phase and the activity of each muscle group of the lower limbs during the walking process,and assist in the selection of the joints of the lower limbs,the setting of the active/passive degrees of freedom of the exoskeleton,and the weight distribution of the exoskeleton components.Exoskeleton energy sources and strategies to reduce exoskeleton energy consumption provide guidance in physiology and kinematics.(2)A method for analyzing human walking energy consumption based on a coupled pendulum model is proposed.A dynamic model of the swing phase and a kinematic model of the dual support phase are established,and the shooting method is used to solve the problem.The effects of joint friction torque and joint energy storage elements on gait and energy consumption are explored.The effect of introducing elastic energy storage elements into different joints of lower limbs on gait and energy consumption was discussed.The model and conclusions can provide reference for the research and design of lower limb assisted exoskeleton,foot prosthesis and biped walking robot.(3)Designed an active unpowered ankle joint exoskeleton,which can realize the recovery and storage of the energy consumption of heel impact and the supporting phase of the ankle joint dorsiflexion during walking,and release it when the wearer pushes the ground through plantar flexion Boost.The core component of the exoskeleton,a clutch mechanism driven by an electromagnet,has been tested for maximum clamping force and frequency response.The experimental results show that the clutch mechanism can meet the requirements of maximum tension,clamping firmness,state switching speed,etc.Requirements for the use of exoskeleton.(4)An active and unpowered dual-joint exoskeleton is designed.The exoskeleton spans the knee joint and the ankle joint.It uses three clutch mechanisms and torsion springs to form an energy storage/discharge system.The human body swings to the end and swings the legs and knees when walking.The joint extension negative work is stored across the joints over time,and the ankle dorsiflexion negative work in the mid-support phase releases assistance when the wearer pushes the ground through plantar flexion.Set up a control system.The state switching of the three clutch mechanisms is jointly controlled by the two signals of the contact state of the forefoot and the ground and the angle of the knee joint.(5)The testers are selected to carry out assisted walking experiments on the ankle joint exoskeleton and the double joint exoskeleton to verify the functionality and power-assisting effect of the two exoskeletons.Collect the tester’s kinematics data,related muscle group EMG signal,oxygen consumption and carbon dioxide output to evaluate the power-assisting effect of the exoskeleton.The experimental results show that the two exoskeletons can help the wearer to walk,and the clutch mechanism assembled by the exoskeleton can switch states in time,and the normal movement of the lower limb joints of the human body is hardly affected when there is no need for assistance.The ankle joint exoskeleton can effectively reduce the wearer’s net walking metabolic rate by about 6.4±1.3%,and the double joint exoskeleton can significantly reduce the activity of related muscle groups.Finally,according to the experimental results,the innovation and limitations of the active unpowered exoskeleton designed based on the passive dynamic walking theory are discussed in detail,the limitations of human experiments,and the feasibility of the exoskeleton progress-improvement direction and the feasibility of further improving the experimental plan.