Design Research On Walking-assisted Flexible Knee Exoskeleton

Lower limb exoskeletons,which is the intelligent equipment that assists the wearer in walking,are now widely used in the medical rehabilitation,defense engineering and transport industry.With the further growth of the population with lower limb disorders,the application of lower limb exoskeleton in daily life has further increased.Exoskeleton knee joint has always been the key research object in the field of exoskeleton because of most people with lower extremity disorders have knee injuries.A long-standing hotspot and difficulty in the field of exoskeleton research was the problem of human-robot knee joint integration in lower limb exoskeletons.Among them,it is the most critical problem of human-robot knee joint movement integration that the instantaneous centers were not match between the knee joint of the lower limb exoskeleton and the human knee joint.Next,there is a lack of an evaluation system that comprehensively evaluates the assistedwalking flexibility of human-robot knee joint from multiple aspects.In response to the above problems,a flexible knee exoskeleton that matches the instantaneous center of knee movement is designed and studied,which improves the motion adaptability of the knee joint during human-robot collaborative movement,and realizes the soft assistance of the exoskeleton knee joint during human walking.In addition,a comprehensive evaluation system for exoskeleton assisted-walking flexibility was proposed based on vitality multi-mode information.The specific research content of the paper is as follows:(1)Design and analysis of flexible knee exoskeleton structure.With the ergonomic theory and the instantaneous mechanism of human knee motion center,a flexible knee exoskeleton with a planar multi-articulated structure is proposed.It can effectively match the instantaneous center of the human knee joint and realize the soft assistance of the knee joint.The rationality about assisted-walking of the flexible knee exoskeleton was verified,based on static working point analysis for different gait phases.(2)Motion modelling and analysis of the flexible knee exoskeleton.The kinematic model of the flexible knee exoskeleton was established by the improved D-H method.By limiting the degree of freedom of the component,the instantaneous error of the human-robot knee motion center is compensated with the redundant degrees in swing phase.In other gait phases,the degrees of freedom of the human knee are equal to the degrees of freedom of the exoskeleton knee.Moreover,the Lagrange equation is used to model the dynamics of the flexible knee exoskeleton on gait phases.(3)The evaluation about assisted-walking flexibility of the flexible knee exoskeleton.A flexible gray comprehensive evaluation model about assisted-walking flexibility of the exoskeleton combined with subjectivity and objectivity is proposed,which uses the analytic hierarchy method to determine the index weight.The subjective qualitative and objective quantitative evaluation indexes of the flexible knee exoskeleton assisted walking performance were established by combining the scale and vital signals.(4)Experimental research of the flexible knee exoskeleton.The assisted-walking simulation experiment was carried out with the flexible knee exoskeleton.It was verified that the flexible knee exoskeleton structure was reasonably designed and the assisted-walking was more flexible by horizontal walking simulation.Furthermore,the experimental scheme with the rigid knee exoskeleton prototype was designed and the platform was built to obtain the performance indicators of assisted-walking.With the simulation data,the evaluation experiment about assisted-walking was carried out.According to the performance indicators,it is verified that the error of human-robot knee motion center is lower,the human-robot coupling effect is better,and the joint assistance is more flexible.At the same time,the rigid knee exoskeleton has certain metabolic lowering performance,and the comprehensive evaluation of walking aid compliance was carried out,which verified the rationality of the evaluation model.According to the human walking mechanism and the mechanism of instantaneous motion center for knee joint,a walking-assisted flexible knee exoskeleton was designed and studied.And its motion model was established and analyzed.Aiming at the one-sided evaluation of the assisted-walking flexibility for exoskeleton,a gray evaluation model was constructed based on analytic hierarchy and its rationality was verified.Experimental research about the flexible knee exoskeleton was carried out.It verified that the evaluation of assisted-walking was better,the matching of human-robot knee motion center was improved,the auxiliary force during humanrobot collaboration was more flexible,the joint angle error during human-robot collaboration were lower.This thesis laid a foundation for the next step of research about the structural optimization design and control strategy of flexible knee exoskeleton.