In this paper, directional stability of road vehicles travelling at time-dependent forward velocity is investigated. The dynamical behaviour of the system is governed by a set of linear ordinary-differential equations with time-varying coefficients. A simple two degrees of freedom (DOF) model is considered, in order to better understand the effects of such a perturbation on the well-established bicycle model, which is frequently used in the literature as a first approach to get useful physical insights on vehicle dynamics. Numerical simulations show significative differences with respect to the prediction of the stability analysis in the case of constant forward speed. A moderately large variation on the forward velocity, indeed, can stabilise the vehicle which is statically unstable. Stability maps are obtained by means of the Floquet theory, with the aim to shed light on the modified vehicle dynamics. A final discussion is provided, which leads to outline the possible practical applications of the present investigation, together with future comprehensive studies.

在本文中，研究了道路车辆以时间相关的前进速度行驶的方向稳定性。系统的动力学行为由一组具有时变系数的线性常微分方程控制。考虑了一个简单的二自由度 (DOF) 模型，以便更好地理解这种扰动对完善的自行车模型的影响，该模型在文献中经常用作获得对车辆有用的物理见解的第一种方法动力学。数值模拟表明，在恒定前进速度的情况下，稳定性分析的预测存在显着差异。前进速度的适度大的变化确实可以稳定静态不稳定的车辆。稳定性图是通过 Floquet 理论获得的，目的是阐明修改后的车辆动力学。提供了最后的讨论，概述了当前调查的可能实际应用以及未来的综合研究。