Research On Static Balance Method Of Paraplegic Assisted Exoskeleton System

With the rapid development of robot technology and the popularization of intelligent rehabilitation medicine,exoskeleton robots used to assist paraplegic patients in rehabilitation training have become a research hotspot.When a paraplegic patient is standing while wearing an exoskeleton,uncontrollable disturbances may cause the human-exoskeleton system to become unbalanced or even fall,causing secondary injury to the patient.In order to avoid this kind of situation,the researchers took the human body balance as the starting point,combined with the biped robot balance strategy to explore the static balance method of the exoskeleton robot.In this paper,by analyzing the balance strategy of normal people when they are disturbed,and combining the differences between human and exoskeleton man-machine systems,a static balance strategy of paraplegic assisted exoskeleton robot is proposed.The main research work is as follows:A static standing disturbance experiment was carried out on normal people.The experimental results show that normal people will adopt ankle joint strategy,ankle-hip hybrid strategy or stride strategy to restore balance when they are disturbed.Considering that paraplegic assisted exoskeleton and ankle joints are passive joints,the static balance recovery strategy can only start from the stride strategy.In the stepping strategy,by analyzing the location of the extrapolated center of mass,the boundary condition between stepping and non-stepping is established.Based on the variable-length inverted pendulum model,the shortest distance from the extrapolated center of mass to the support domain is used as the calculation method of stability.The analysis shows that the optimal point of mass center drop when the human body is disturbed should be located between the two feet.In order to quantify the relationship between the disturbance and the centroid drop point,this paper compares the advantages and disadvantages of commonly used regression models based on the disturbance step data,and finally selects the gradient lifting regression tree model to predict the dynamic characteristics of the centroid,and the results show that the centroid drop The point differs by about 10 mm,and the center of mass velocity differs by about 15mm/s.In order to complete the paraplegic assisted exoskeleton static balance strategy,it is necessary to determine the crutches drop point and the foot drop point.Because the paraplegic assisted exoskeleton robot is limited by the freedom of the lower limb joints,the legs can only move in the sagittal plane.In order to resist the disturbance in the oblique direction,it is necessary to use crutches to share its lateral velocity component.In this paper,using the predicted centroid drop point data combined with the static stability index,a feasible crutch drop point area is given.Based on the experimental data,a Gaussian distribution of the crutch drop point is established in this area,and the relationship between the disturbance force and the Gaussian distribution is fitted to determine The crutches drop point;at the same time,on the basis of the balance between the stability and the arm support,the optimal foot drop point is calculated by the optimization method.Based on Gazebo,the human-exoskeleton model of paraplegia assisted exoskeleton was built to realize the algorithm of joint controller,inverse kinematics and static balance strategy.The effectiveness of the static balance strategy was verified on the simulation platform.The paraplegic-assisted exoskeleton static balance strategy proposed in this paper achieves the balance recovery of the man-exoskeleton system when standing still.When paraplegic patients wearing exoskeleton are disturbed while standing,they can achieve a new state of balance by moving crutches and stepping,and the safety is improved.