A parametric study of the lateral dynamics of a nonlinear four-wheel road-vehicle model.

摘要

This study presents the influence of basic vehicle parameters on the lateral dynamics of a four-wheel road-vehicle model. To encompass the majority of the vehicles currently on public roads in the us and other countries, the road-vehicle model in this study uses three different nominal parameter sets corresponding to small, medium and large (S.U.V.) vehicles. Parameter values from each set are changed individually from their nominal values through a finite range, and the effect of these changes on the dynamics of the model are observed. A step-steer and total vehicle velocity of constant magnitude are used as inputs for the model. An analysis where several vehicle parameters are changed simultaneously is used to study parameter interaction. Response characteristics, both transient and steady-state, are chosen as indicators of the lateral dynamics.; The governing differential equations of the road-vehicle model are solved using a fourth-order Runge-Kutta integration programmed in MATLAB—a mathematical programming software. The road-vehicle model in this study is a rigid body approximation that considers the effects of lateral weight transfer on the normal load of the tires. The rigid-body approximation allows this study to have broad scope and applications because the vehicle parameters considered in this study are basic and general to any road-vehicle. The model used in this study does not include characteristics that have to be particular to a specific vehicle, such as suspension system architecture, axle kinematics, compliance, and suspension component stiffness. A piece-wise tire approximation represents the nonlinear lateral force produced by the tires. This tire model is compared with the Magic Formula nonlinear tire model. Simple and multiple regression analysis techniques are used in this study to quantify the observations derived from the results.; The results of this study show that the longitudinal mass center position is the most influential vehicle parameter and that its influence on the response characteristics chosen for this study is almost always exponential in nature. Further results suggest that the other vehicle parameters considered in this study influence the response characteristics steady state lateral velocity, steady state angular velocity, and angular velocity overshoot in a way that is approximately linear. The other response characteristics appear to be influenced in a nonlinear way by the simultaneous variation of the vehicle parameters.