Intelligent Wheelchair Passability Study In The Face Of Gravel Road Surface

The number of disabled and elderly people who travel with the help of smart wheelchairs in today’s society is increasing year by year,and with the increase of travel range,the complex road conditions have put forward new requirements for smart wheelchairs.In this thesis,with the support of Shenyang Institute of Automation Research Laboratory Development Fund,we conduct a theoretical study on the passability of intelligent wheelchairs under gravel road surface with the help of vehicle ground mechanics theory,so as to establish a wheel-surface contact dynamics model;simulate and model the wheelchair and gravel road surface,propose to describe the wheelchair model by using the finite element method and the gravel road surface model by using the discrete element method,and coupling the finite element model and the discrete element model to carry out the passability simulation.The coupling between the finite element model and the discrete element model i s set up to perform the pass-by simulation analysis;the intelligent wheelchair pass-by test is conducted to verify the validity of the simulation model using the test results;the test and simulation of various working conditions are conducted to compare the changes of pass-by parameters under different working conditions.The main research contents of this thesis are as follows:Based on the vehicle ground mechanics theory,the compressive characteristic model and shear characteristic model are studied;the wheel soil dynamics model applicable to this study is constructed,and the passability evaluation parameters(drawbar pull,driving moment,wheel sinkage and traction efficiency)are determined.Matlab software is used to input the kinetic model,and tests are used to verify that the theoretical model has validity.Establish a simulation model of intelligent wheelchair passability under gravel road surface.Firstly,the physical properties of gravel were tested to determine the macro-mechanical parameters,and then the triaxial compression test was conducted to determine the fine mechanical parameters;and the simulation of triaxial compression test under the same working conditions was carried out to calibrate the parameters of discrete element particles;the discrete element method was used to generate the discrete element pavement model in the Ls-Dyna pre-processing software Ls-Prepost and the self-weight compacting was carried out;the wheelchair tires were fine-grained finite element modeling,and establish the wheelchair whole vehicle finite element model.Then,we performed the passability simulation analysis of the intelligent wheelchair under gravel road surface,and used the coupled finite element-discrete element simulation analysis method to set up the finite element wheelchair model and the discrete element gravel road surface model and perform the passability simulation analysis to obtain the drawbar pull,driving moment,wheel sinkage and traction efficiency at the wheel position.Finally,the passability simulation analysis with different speeds,with and without tread control and with different tire pressures were carried out to study the changes of passability parameters respectively.A gravel road surface intelligent wheelchair passability test platform was built,and the road driving test was conducted according to the simulation conditions.The drawbar pull and Driving moment of the wheelchair during the driving process are obtained through the six-dimensional wheel force sensor,and the test results are compared with the simulation results to draw the conclusion that they are consistent,and to verify the effectiveness of the finite-element-discrete-element coupled simulation method.This study contributes to the study of wheelchair passability by conducting a theoretical study of wheel-soil contact dynamics and performing simulation and experimental analysis.