The Modeling And Simulation Of Seventeen-Degree-of-Freedom Vehicle

Due to the prosperity of the automobile industry, the research of vehicle dynamic has been developing quickly. Kinds of vehicle simulation model were established. For instance, the seven-degree-of-freedom model is used to evaluate the ride performance of vehicle with the input from the road. And the three-degree-of-freedom model is applied for analyzing the handling characteristics under the steering angle input. However, these models developed for one certain input can't satisfy the simulation request because that there always is more than one input when vehicle runs on the road. It is quite necessary to derive a model that can be used in various inputs.At the beginning, this paper states the history of the vehicle dynamic and introduces the derivation of some simple vehicle models. Then a seventeen-degree-of-freedom vehicle mathematical model is derived. Because of the space movement of the vehicle body, the forces acting on the body include not only the tire forces, the aerodynamic forces and the gravitational forces, but also the inertia forces such as the Coriolis forces and centrifugal forces when considered in the body reference system. So it is very difficult to derive the equations by the normal multi-body dynamics methods. D'Alembert principle of inertia is used to derive the differential equations in this paper. The general accelerations are defined to calculate the inertia forces and moments, which make the derivation more simple and effective.The vehicle dynamics model includes a set of coupled differential equations. It is quite time consuming to solve these equations using the usual methods. To satisfy the real-time simulation request, an iterative calculation method is used in this paper. Substituting the displacements and speeds of the state variables of the last step time in the differential equations, the accelerations of the state variables are obtained easily. Then the speeds and displacements of the next step time are calculated using the accelerations and step time. This iterative method is much quicker than the usual methods in solving differential equations.