ABSTRACT

This study deals with drifting as one of the most important nonlinearities in vehicle dynamics. A four-wheel vehicle model is used to calculate the equilibria in planar motion, numerically, by introducing an assumption on constant longitudinal tyre slips. Other than the unstable drifting points that were reported by previous researchers, a new pair of drifting equilibria are identified and the difference between the two types is studied. The phase portrait approach is used to identify the type of these equilibria, and they reveal the type of instability in the primary and the secondary drifting points, and provide control suggestions to stabilise the drifting equilibria. It is observed that the rear-wheel-drive vehicles have primary drifting equilibria, while the four-wheel-drive vehicles have secondary drifting equilibria. There is a transition point between the primary and the secondary drifting types when the front longitudinal tyre slips increase from zero to saturation. It is further shown that primary drifting becomes stable by regulating the yaw rate at the equilibrium value; whereas the secondary drifting may be stabilised through a constant forward velocity. The stabilisation methods are applied through control designs and validated in simulations.

摘要

本研究将漂移视为车辆动力学中最重要的非线性之一。四轮车辆模型用于计算平面运动中的平衡，通过引入恒定纵向轮胎滑移的假设来进行数值计算。除了先前研究人员报告的不稳定漂移点外，还确定了一对新的漂移平衡点，并研究了这两种类型之间的差异。相图方法用于识别这些平衡的类型，它们揭示了初级和次级漂移点的不稳定性类型，并提供了稳定漂移平衡的控制建议。观察到后轮驱动车辆具有初级漂移平衡，而四轮驱动车辆具有次级漂移平衡。当前纵向轮胎打滑从零增加到饱和时，主要和次要漂移类型之间存在过渡点。进一步表明，通过将偏航率调节到平衡值，初级漂移变得稳定；而二次漂移可以通过恒定的前进速度来稳定。稳定方法通过控制设计应用并在模拟中验证。