Balance Index Of Paraplegic Walking Exoskeleton Based On Human Machine Dynamics

Paraplegic assisted exoskeleton robot plays an increasingly prominent role in the field of rehabilitation medicine.In order to ensure the safety of patients using exoskeleton,the balance of human-exoskeleton system has become a research hotspot.The primary goal of maintaining balance is to distinguish and quantify balance,that is,a reliable balance index is needed.In the past,there were many researches on the balance indexes of human body and robot,but there was insufficient research on the balance indexes of human-exoskeleton system.Therefore,this thesis proposes two balance indexes for human-exoskeleton sys-tem.One is the balance index based on the improved stability pyramid,which works well when the minimum stable angle is greater than zero.Another is the balance index based on centroid dynamics,which can supplement the case that the minimum stability angle is less than zero.The effectiveness of the two indicators is verified by experiments.The specific research contents of this thesis are as follows:Based on the stable pyramid theory,the balance of human-exoskeleton system is studied.Firstly,the principle of the traditional stable pyramid is introduced,and then how to apply it to the human-exoskeleton system is analyzed.It is found that this method has some problems,such as no threshold,too subjective weight coefficient of balance index,so it is optimized and improved.The threshold range of the balance index is determined according to the functional stability boundary theory,and the stability margin is intro-duced to dynamically adjust the weight coefficient of the balance index.By improving the stability cone method,the balance index of the improved stability cone is proposed,which can more objectively measure the balance degree of human-exoskeleton system.Based on the centroid dynamics,the balance of human-exoskeleton system is studied.The changes of centroid angular momentum,centroid acceleration and centroid stability margin in the stable walking process of human-exoskeleton system are analyzed respec-tively.It is found that these three variables can be used as important parameters of balance index.A balance index based on centroid dynamics is established by linear weighting method,Particle swarm optimization algorithm is selected to optimize the weight coeffi-cient in the index,and a sagittal balance index suitable for exoskeleton human-exoskeleton system is proposed.For the two balance indexes proposed in this thesis,the motion capture system Vicon is used for experimental verification.The static dumping experiment and dynamic walk-ing experiment of wearing AIDER exoskeleton are designed.Through the static dumping experiment,the threshold range based on the improved balance index of stability pyramid is determined.The thresholds of four-point support and three-point support are 100 and1100 respectively.And it is verified that this index has high effectiveness when the min-imum stability angle is greater than zero.At the same time,it is verified that the balance index based on centroid dynamics can supplement the case that the minimum stability an-gle is less than zero,and the threshold is 0.06,it can effectively distinguish whether the human-exoskeleton system is balanced or not when walking.