基于路表分形摩擦理论的整车雨天制动性能模拟

Simulation of vehicle braking performance on rainy days based on pavement surface fractal friction theory

采用一种考虑橡胶-路面摩擦特性与水膜动水压力的雨天车辆制动模拟方法,研究了积水沥青路面上车辆的制动性能。首先运用路表分形摩擦理论,基于路面功率谱和橡胶的复模量计算出橡胶-路面的动摩擦因数。然后建立轮胎有限元滑水模型,分析了不同行驶速度及水膜厚度下轮胎-水膜-路面接触力变化规律。在此基础上,建立整车动力模型,基于车辆防抱死制动机理模拟评估了积水直线与弯道路面上整车制动性能。研究表明:与干燥状态相比,潮湿状态下橡胶-路面动摩擦因数下降了13%～34%;轮胎滑水过程中,随着轮胎行驶速度的增加,轮胎-路面接触力逐渐减小、水流竖向托举力逐渐增大,水膜厚度的增加也会产生相同的效果;较低的车辆行驶速度、较小的路表水膜厚度以及防抱死系统,都能有效降低车辆制动距离;相比于单个车轮的临界水漂速度,采用整车模型分析积水路面车辆行驶状况更切合实际状态。

To investigate vehicle braking performance on wet asphalt pavement,a method was developed to simulate the vehicle braking process on rainy days considering rubber-pavement friction and water film hydrodynamic force.Firstly,the pavement surface fractal friction theory was applied to calculate the rubber-pavement kinetic friction coefficient based on pavement surface power spectrum and rubber complex modulus.Secondly,a finite element tire hydroplaning model was constructed to determine the tire-water film-pavement interaction force with different vehicle velocity and water film thickness.Based on these,a full vehicle dynamic model was constructed to evaluate the vehicle braking performance on wet straight road and curved road,and vehicle anti-lock braking mechanism was analyzed.Research results show that the rubber-pavement kinetic friction coefficient declines by 13%~34%when pavement becomes wet.In the tire hydroplaning process,tire-pavement contact force rises and water uplifting force drops with the increase in vehicle velocity and water film thickness.The lower vehicle velocity,the smaller water film thickness and the equipment of anti-lock braking system are useful in reducing vehicle braking distance.Compared with critical tire hydroplaning speed,the full vehicle model is superior in coinciding with the actual situation in evaluating vehicle driving performance on wet pavement.