K型线与回旋线在卵形曲线上行车稳定性分析

Analysis of driving stability of K-curve and clothoid on oval curve

为研究K型线作为公路缓和曲线的可行性,对比分析K型线和回旋线在卵形曲线中车辆横向加速度、横摆角速度、横向荷载偏移率及横向加速度变化率4种指标的差异,分析车辆在K型线上行驶的行车稳定性。根据K型线数学模型和设置方法,求解K型线的逐桩坐标,并将其导入动力学仿真软件CarSim,建立小客车在K型线上行驶的仿真模型。通过改变缓和曲线起、终点曲率半径大小,从K型线和回旋线的线形变化情况,车辆操纵稳定性以及驾驶人舒适性3个方面对小客车在不同半径卵形曲线上的行驶状态进行了仿真试验。研究结果表明:在相同设计指标的情况下,K型线平面线形的弯曲程度稍缓于回旋线,且圆曲线半径越小,两者弯曲程度差异越大;车辆在K型线上的行驶轨迹曲率为均匀连续的非线性变化,可用作过渡2种不同的线形;K型线起、终点曲率半径比值越小,K型线扁平程度参数k值越大,K型线的曲率变化情况越接近于线性变化;车辆在K型线上的横向加速度变化率在曲线前半段小于回旋线,在后半段大于回旋线,当设计指标符合路线设计规范的规定时,其横向加速度变化率满足驾驶人舒适性要求;车辆在K型线上的稳定性参数始终小于回旋线,能够满足车辆稳定性要求,且稳定性更好。该研究证明K型线可作为缓和曲线引入公路卵形曲线线形设计,增加公路平面设计曲线类型,增加路线设计的多样性和灵活性。

To study the feasibility of K-curve as highway transition curve, the differences of vehicle lateral acceleration, yaw rate, lateral load deviation rate and lateral acceleration change rate between K-curve and clothoid on oval curve were compared and analyzed, and the driving stability of vehicle running on the K-curve was studied. According to the mathematical model and setting method of the K-curve, the pile-by-step coordinates of the K-curve were solved and imported into the dynamic simulation software CarSim, and the simulation model of car running on the K-curve was established. By changing the radius of curvature at the beginning and the end of the transition curve, the driving state of the passenger car on the oval curve was simulated from the three aspects of the linear change of K-curve and clothoid, vehicle handling stability and driver comfort. The results show that under the same design index, the bending degree of K-curve is slightly slower than that of clothoid, and the smaller the radius of circular curve is, the greater the difference between them is. The curvature of the driving track of the vehicle on the K-curve is a uniform and continuous nonlinear change, which can be used as a transition between two different lines. The smaller the ratio of radius of curvature between the beginning and the end of K-curve, the larger the value of flat degree parameters k of K-curve, the closer the change of curvature of K-curve is to the linear change. The change rate of the lateral acceleration of the vehicle on the K-curve is smaller in the first half of the curve than that of the clothoid, and larger in the second half of the curve than that of the clothoid. When the design index conforms to the provisions of the route design specification, the change rate of the lateral acceleration meets the requirements of the driver’s comfort, and the stability parameters of the vehicle on the K-curve are always smaller than that of the clothoid, which can meet the requirements of vehicle stability, and the stability is better. It proves that K-curve can be used as transition curve to design oval curve alignment, widen highway plane design curve type, and increase the diversity and flexibility of line design. 2 tabs, 10 figs, 31 refs.