The Improvement Of The Simulation Software For The Wheel Rolling On The Soft Ground

Vehicle terramechanics is a subject that combines vehicle dynamics and soil mechanics to study the interaction process between vehicles and the ground.In vehicle terramechanics research fields,scholars have studied the wheels or tracked vehicles that are suitable for farmland,marsh,desert,beach,the moon and other kinds of complex driving ground,a lot of theoretical analysis and experimental demonstration are carried out to improve the trafficability characteristic of vehicles,and have achieved abundant research results,in agriculture,military detection and other fields have made tremendous contributions.In the research process of vehicle terramechanics,domestic and foreign scholars use a variety of methods to model the mathematical relationship modeling between vehicles and the ground,these methods will be divided into the following five categories according to the development process of vehicle terramechanics : the pure experience method,the semi empirical method,the basic theory research method,the simulation test method and the electronic computer simulation method.In these methods,the basic theory research method and the electronic computer simulation method are most widely used,and with the maturity of computer technology,more and more scholars have combined the two methods,establishing the relationship model on computer of vehicle and ground based on theoretical analysis,using computer simulation can substitute pure physical test,come to a conclusion through the analysis of the simulation results.One of the disadvantages of using the basic theory research method is that the method follows the continuum mechanics method and does not conform to the actual situation of soil ground.The discrete element method is a theoretical method used to analyze the mechanical behavior of discontinuous medium.By separating the research object into a large number of units,the motion process is decomposed into a large number of very short time sets.Each unit satisfies Newton’s second law at every moment and iteratively superposes all the motion moments.The change of the whole motion form of the dynamic process of the object is reflected by the change of the object’s position at every moment.Based on the basic idea of the discrete element method,it is very reasonable and effective to use the discrete element method to study soil terramechanics.Therefore,after the discrete element method has been widely applied,many scholars have replaced the continuous medium mechanics method in the basic theoretical research by discrete element method.This paper takes the interaction process between the wheel and the ground as the research object,and uses the method of combining the discrete element and the computer simulation simulation.Based on the discrete element calculation simulation software Agri DEM developed by the project group,the 3D simulation and simulation function of the wheel on the soft ground rolling process is realized.This paper first uses the discrete element method to establish the three-dimensional model of soil ground and wheel.Then the contact mechanics model is applied to analyze and solve the interaction process between the wheel and the ground,and according to the calculated force,calculate the change of position and speed of the wheel and soil particles at each time.Finally,by iterating all the motion moments of the position coordinates of the wheel and the soil particles,the simulation dynamic diagram of the rolling process of the vehicle on the soil surface is obtained.By testing the program,we can learn that the following main functions are achieved in this paper: users can freely set up the way of modeling soil and wheel;users can freely set up all the mechanical parameters of the soil surface and wheel;and the performance analysis of the wheel moveme nt process.Among them,the free setting of soil surface modeling is manifested as : the ground model can choose two kinds of soil particle generation method : single particle and multiple particle,each generation method can freely choose particle shape and particle size distribution.The free setting of wheel modeling is shown as: the wheel model can choose two kinds of wheel type : rigid wheel or elastic wheel,each type of wheel provides the model of different wheel number.The structure parameters of the selected wheel can be set freely,and the wheel will also be able to simulate the driving wheel or the driven wheel.The performance analysis of the wheel movement process will be carried out by the relationship graph,such as speed-time relation graph and so on.This program can meet the simulation requirements of different users.The simulation of soil surface modeling and mechanical parameters can achieve the simulation of different driving fields such as fields,swamps and deserts.The influence of wheel structural parameters on wheel trafficability characteristic can be studied by setting up wheel modeling method.C hanges in mechanical parameters of wheels can be used to study mechanical factors affecting wheel dynamic performance.The performance analysis diagram can be used to analyze the correctness of the simulation results.According to the test results,this program has achieved the purpose of research: design a new tool that can provide theoretical basis for vehicle design optimization.