Implementation and verification of adaptive longitudinal traction control

Human in the loop (HIL) simulation has experienced a significant increase in popularity in recent years. In this work, a novel approach to traction control is developed and implemented in a HIL environment, exploiting the significant advantages of framing the problem in a manner that more closely matches how a human expert drives a vehicle. An adaptive gradient ascent algorithm is at the heart of the proposed solution to longitudinal traction control. A real-time implementation of the gradient ascent algorithm is developed using linear operator techniques, even though the tyre–ground interface is highly non-linear. The adaptive traction control algorithm is based on two separate, but related, estimation algorithms that estimate both the instantaneous traction force and a unique predictive traction force model. This adaptive control algorithm, the necessary estimation algorithms and their real-time implementation are described in this work. The results, when implemented as a driver assist application on a 6-DOF motion platform, with a HIL, are also presented. This work demonstrates the utility of a 6-DOF motion platform in developing and verifying vehicle control algorithms with a HIL.     

A vehicle ABS adaptive sliding-mode control algorithm based on the vehicle velocity estimation and tyre/road friction coefficient estimations

A sliding-mode observer is designed to estimate the vehicle velocity with the measured vehicle acceleration, the wheel speeds and the braking torques. Based on the Burckhardt tyre model, the extended Kalman filter is designed to estimate the parameters of the Burckhardt model with the estimated vehicle velocity, the measured wheel speeds and the vehicle acceleration. According to the estimated parameters of the Burckhardt tyre model, the tyre/road friction coefficients and the optimal slip ratios are calculated. A vehicle adaptive sliding-mode control (SMC) algorithm is presented with the estimated vehicle velocity, the tyre/road friction coefficients and the optimal slip ratios. And the adjustment method of the sliding-mode gain factors is discussed. Based on the adaptive SMC algorithm, a vehicle's antilock braking system (ABS) control system model is built with the Simulink Toolbox. Under the single-road condition as well as the different road conditions, the performance of the vehicle ABS system is simulated with the vehicle velocity observer, the tyre/road friction coefficient estimator and the adaptive SMC algorithm. The results indicate that the estimated errors of the vehicle velocity and the tyre/road friction coefficients are acceptable and the vehicle ABS adaptive SMC algorithm is effective. So the proposed adaptive SMC algorithm can be used to control the vehicle ABS without the information of the vehicle velocity and the road conditions.     

Literature review and fundamental approaches for vehicle and tire state estimation*

ABSTRACT

Most modern day automotive chassis control systems employ a feedback control structure. Therefore, real-time estimates of the vehicle dynamic states and tire-road contact parameters are invaluable for enhancing the performance of vehicle control systems, such as anti-lock brake system (ABS) and electronic stability program (ESP). Today's production vehicles are equipped with onboard sensors (e.g. a 3-axis accelerometer, 3-axis gyroscope, steering wheel angle sensor, and wheel speed sensors), which when used in conjunction with certain model-based or kinematics-based observers can be used to identify relevant tire and vehicle states for optimal control of comfort, stability and handling. Vehicle state estimation is becoming ever more relevant with the increased sophistication of chassis control systems. This paper presents a comprehensive overview of the state-of-the-art in the field of vehicle and tire state estimation. It is expected to serve as a resource for researchers interested in developing vehicle state estimation algorithms for usage in advanced vehicle control and safety systems.     

站桥同位合建上盖钢箱梁“π”形支架门吊架设技术

为了解决繁华城区既有道路有限空间内快速、安全架设小半径曲线钢箱梁的施工难题,依托地铁车站柱网形式及围护结构冠梁为基础,采用高位门吊及"π"形支架体系架设方案,实现了在空间受限情况下,地铁车站、市政道路及高架桥三者的和谐统一。以合肥南北高架一号线Ⅰ标明挖地铁芜湖路站及其同位合建的上盖小半径反曲线钢箱梁为例,阐述站桥同位合建理念及"π"形支架联合门吊架梁方案,并对架梁支架及架梁对地铁车站的影响进行力学分析。得出以下结论:1)站桥同位合建共用一个走廊,既减少拆迁,又节约投资,为繁华城区有限空间立体开发提出了解决思路;2)利用下卧地铁车站柱网及桩顶冠梁,"π"形支架联合门吊架设,支架简单可靠、门吊快速安全,平行流水作业,安全、快速、经济,很好地克服了"S"形小半径反向曲线反超高的空间扭曲结构曲线拟合难、安全风险大的困难;3)"π"形支架支撑体系利用了下部车站柱网结构,能满足安全性要求。     

考虑空间相关性的行人宏观安全研究

为了探究行人事故的发生机理,分析影响行人交通安全的显著因素,收集上海市中心城区263个交通分析小区（TAZ）的行人事故、道路、人口及土地利用数据,并开展行人宏观安全研究。考虑到TAZ之间存在的空间相关性,建立考虑空间相关性的贝叶斯负二项条件自回归模型,在条件自回归模型中对比分析了5种不同的空间权重矩阵,包括0~1邻接矩阵、边界长度矩阵、分析单元中心距离倒数矩阵、事故空间中心距离倒数矩阵这4种既有矩阵,以及首次引入的宏观安全建模中的分析单元中心距离多阶矩阵。结果表明：分析单元中心距离多阶矩阵的模型拟合效果和事故预测准确度均显著优于既有的4种空间权重矩阵,证明了在宏观安全建模过程中考虑研究对象交通特征（居民步行平均出行距离等）的必要性;人口数量、主干道长度、次干道长度、路网密度等因素均与行人事故呈现显著正相关,平均交叉口间距、三路交叉口比例等因素与行人事故呈显著负相关;相较于高等、低等土地利用强度,中等土地利用强度对行人事故的影响最大。     

非常态下城市道路交通检测器布局优化方法

为了使城市道路上布设的交通检测器能够实时、准确地提供路网动态交通流信息,并最大程度地节约经济成本,通过仿真对交通异常事件下城市道路交通流量和车辆延误进行了估计,并利用模糊聚类分析法、回归分析法和车辆延误估计模型,研究了路网在非常态下的检测器空间位置以及空间密度的布局优化方法;通过一个算例,对提出的检测器布局优化方法进行了验证分析,并得出了算例中检测器布局的优化方案。结果表明:所提出的检测器布局优化方法是可行的。     

基于改进近似极大似然估计的弯道车速预警

超速行驶是道路曲线段事故发生的主要致因,基于智能车辆的提前预警系统是行之有效的安全辅助措施。提出了一种新的弯道车速预警算法,其采用改进的近似极大似然估计拟合曲线半径,改进算法采用最小平方估计取代了传统的平均3点估计。通过模拟实验得到,在不同数量的采样点、噪声和弧长下,改进的估计算法的精度都要高于传统的极大似然估计。根据预估的半径,车辆控制器便能得到相应的安全行驶车速。最后论文根据车辆实际车速和安全车速阈值的差值计算了车辆控制器发出预警信号时车辆与曲线入口之间的距离。     

非接触式胎压安全报警系统的研究

在现代汽车上,轮胎气压对汽车的安全性、舒适性、经济性以及操纵稳定性都有非常大的影响。为了能更好地对轮胎气压起到更准确的监控,笔者在对已有的类似系统进行了简单介绍后,通过半径比较法和频率修正法设计研究了一种非接触式胎压安全报警系统。最后采用了一个应用实例,说明了该系统的实用性和科学性。     

非开挖水平定向穿越铺设地下管线施工技术

简要介绍了非开挖水平定向穿越铺设地下管线施工技术的优点,重点阐述了该施工技术成败关键在于施工前对周围原有管网的勘察、钻进泥浆的选择和配制以及优化设计的最佳轨迹曲线这几个重要环节。     

双前桥转向系统瞬时转动中心理论分析及二轴转角的确定

建立了双前桥转向系统瞬时转动中心的数学模型,进行了理论分析和数学公式推导,得出了转动中心位置的一般公式以及一轴、二轴转角关系式。以某车型为例讨论了二轴转角、偏移和转动半径分别在不同双后轴距离处以及一轴不同转角条件下的变化规律。结果表明,瞬时转动中心不在后二轴中心线上,而是相对后二轴中心向后偏移,且偏移量随后二轴轴距增大而增大;前一轴转角对于瞬时转动中心的影响不大。转向半径随着后二轴轴距增大而增大;当一轴转角较小时,转向半径变化很大,当一轴转角最大时转向半径达到最小。