Development Of Three Dimensional Discrete Element Tire Model For Off-road

In order to improve the vehicle mobility for off-road vehicles and military vehicles，Using the simulation method to develop their handling, riding comfort, accelerating andbraking performance is an important way. Also the development and validationof the electric controlling system of such vehicle chassis need the virtual simulationtechnology, the key of which is the tire model for soft ground. Hence, studying of theoff-road tire dynamic model has become a hot point. This paper develops the off-road tiredynamic model of discrete element in MATLAB, based on the theory of discrete elementand the comparison of the tire-soil interface models. A simulation and analysis of verticalloading case, pure longitudinal slip case and combined slip case are done andthe simulation results have a good agreement with other research papers. The followingare the main research contents:1. A comparative analysis of tire-soil interface models is done. Based onmechanics theory and model complexity, this paper compares and analyzes the basicmodels of the tire-soil contact force, including the normal stress model, the shear stressmodel, the bulldozing force model and the multiple pass model. The characteristics andapplicable scope of these models are obtained to lay the foundation for the selection of thetire-soil interface model.2. Three dimensional discrete element tire model of the off-road is studied. Based onthe theory of discrete element, the tread and sidewalls of tire are respectively divided intoNmlumped mass elements. The sidewalls are directly connected to the wheel rim by elasticand damping element to simulate the tire elastic and pressure. The sidewall element isconnected with the tread element, bearing the force of the tread element and the groundforces, including the normal stress, the shear stress and the bulldozing force. The treadelement is only connected to the sidewall element. It has three translational degrees offreedom and it mainly bearing the normal stress and the shear stress of the ground. The wheel rim is simplified into a rigid body with six degrees of freedom, as a bearing body ofthe tire’s six component force. This paper respectively deduces the dynamic, static andkinematic equations of the wheel rim, the tread element and the sidewall element, basedon the theory of multi-body dynamics. Based on the mathematical method, a dynamiccalculation method which decides the entry angle and exit angle of the contact element isdeveloped. Thus, three dimensional discrete element tire model of the off-road is built.3. Three dimensional discrete element tire model is simulated and analyzed. In orderto simulate and calculate three dimensional discrete element tire model of the off-road,this paper builds the model in MATLAB, based on the comparative analysis of variousODE solvers in MATLAB. A simulation and analysis of vertical loading case,pure longitudinal slip case and combined slip case are done using the model built in thispaper. The calculation result of tire force and the distribution regularities of the normalstress, the shear stress and the bulldozing force of these cases are obtained. And thedistribution regularities of the normal stress, the shear stress and the bulldozing force havea good agreement with other research papers, proving the validity of the model built inthis paper.