ANALYSIS OF DRIVING MODE EFFECT ON VEHICLE STABILITY

摘要

Nowadays the typical method of dynamics analysis of vehicle stability is based on the nonlinear vehicle model deriving from the classic two degrees of freedom (2DOF) linear vehicle model. The features of system stability are obtained by phase space analysis, state variables analysis and so on. But these conclusions are drawn under the assumption that the driving mode effect on vehicle stability is neglected in vehicle model. In fact, there are strikingly obvious stability differences between front-wheel-drive vehicle and rear-wheel-drive vehicle at the high speed. Aiming at the above problem, this paper has investigated effect of driving mode on vehicle stability. A uniform slip equation of tyre longitudinal slip is proposed. The uniform slip equation guarantees both the calculation validity and the simulation convenience. Based on the uniform slip equation and Magic Tyre Formula, a 5DOF (longitudinal velocity, lateral velocity, yaw rate, front wheel rotational velocity and rear wheel rotational velocity) planar motion nonlinear dynamics vehicle system model is established under the consideration of driving mode. Many simulations are carried out on the basis of the 5DOF nonlinear mechanical vehicle model with different driving modes and different front steering angles respectively. The simulation results, including system globe phase portraits, system state variables, vehicle tracks and tyre force distributions, show that the driving mode has great effects on vehicle stability. The present vehicle models without considering driving mode fail to estimate the system stability region exactly.