基于横向安全距离模型的主动避障算法

现有的安全距离模型是基于纵向相对车速或减速度值建立的,没有考虑移动目标的横向运动特性。本文利用移动目标横穿马路的速度、相对位置,建立横向安全距离模型,并提出一种基于横向安全距离模型的主动避障算法。首先,根据横向移动目标横穿马路的速度、相对位置和自车的制动距离建立横向安全距离模型,设计主动避障算法。接着,为计及路面条件对制动效果的影响,引入当前行驶路面估算的附着系数峰值估算最大制动减速度,约束目标避障减速度,并调整制动强度,以适应不同路况的安全避障行驶。最后,以典型横向移动目标骑行者作为研究对象,通过PreScan/Simulink/CarSim联合仿真验证避障算法的有效性。结果表明:基于横向安全距离模型的主动避障算法能有效避免与骑行者碰撞,提高行车的主动安全性。     

视线遮挡条件下面向弱势道路使用者的避撞策略研究

由于视线障碍物造成的“鬼探头”事故已经成为当前城市道路交通事故的主要类型之一。针对汽车碰撞视线遮挡条件下横穿的弱势道路使用者(VRU)的场景, 设计了1种基于碰撞时间比和安全制动距离的避撞策略, 建立车辆与VRU的交通状态数学模型, 分析“鬼探头”场景下的制动避撞临界距离。结合临界距离和车辆与VRU的碰撞时间比, 将可以避免碰撞的场景分为3种工况, 分别采用不同的制动减速度, 建立自动紧急制动避撞策略。通过Euro NCAP CPNC测试场景对该策略与传统TTC制动算法进行比较分析。结果表明, 在Euro NCAP CPNC测试场景中, 自车利用该避撞策略在理想情况下能够在更高的车速情况下完成避撞; 在不能避免碰撞的高速行驶工况中较传统TTC算法能够更加有效降低碰撞速度, 同时降低事故重伤风险和死亡风险, 提高车辆的安全性。      

Feedback brake distribution control for minimum pitch

The distribution of brake forces between front and rear axles of a vehicle is typically specified such that the same level of brake force coefficient is imposed at both front and rear wheels. This condition is known as ‘ideal’ distribution and it is required to deliver the maximum vehicle deceleration and minimum braking distance. For subcritical braking conditions, the deceleration demand may be delivered by different distributions between front and rear braking forces. In this research we show how to obtain the optimal distribution which minimises the pitch angle of a vehicle and hence enhances driver subjective feel during braking. A vehicle model including suspension geometry features is adopted. The problem of the minimum pitch brake distribution for a varying deceleration level demand is solved by means of a model predictive control (MPC) technique. To address the problem of the undesirable pitch rebound caused by a full-stop of the vehicle, a second controller is designed and implemented independently from the braking distribution in use. An extended Kalman filter is designed for state estimation and implemented in a high fidelity environment together with the MPC strategy. The proposed solution is compared with the reference ‘ideal’ distribution as well as another previous feed-forward solution.     

考虑预碰撞时间的自动紧急制动系统分层控制策略研究

为提升汽车的主动安全,对车辆自动紧急制动系统控制策略进行研究。利用分层控制的思想对控制策略进行建模,上层控制器为对车辆制动减速度进行决策的预碰撞时间模型,根据汽车追尾事故深度调查的驾驶员紧急制动数据分析制动系统的制动减速度,在考虑舒适性的条件下确定预碰撞时间阈值。下层控制器按照上层控制器输出的制动减速度,分析车辆轮胎模型和制动系统的关系,通过PID控制调节制动压力对车辆进行控制。在安全评价规程标准工况下验证控制策略的可靠性,通过追尾事故场景的重建来验证控制策略的有效性。仿真结果表明:设计的控制策略在相对车速65km/h以内时能有效避撞,而高于65km/h时能最大程度地降低碰撞车速,减小伤害。     

基于CAN总线的安全车距保持系统

在设计油门和制动执行器硬件以及各部分电控单元基础上,通过对相应的控制算法、信号采集和处理算法、CAN协议和通信软件的设计,构成基于CAN总线的安全车距保持系统。通过试验结果表明所设计的CAN控制网络能满足该系统的使用要求。     

ISG hybrid powertrain: a rule-based driver model incorporating look-ahead information

According to European regulations, if the amount of regenerative braking is determined by the travel of the brake pedal, more stringent standards must be applied, otherwise it may adversely affect the existing vehicle safety system. The use of engine or vehicle speed to derive regenerative braking is one way to avoid strict design standards, but this introduces discontinuity in powertrain torque when the driver releases the acceleration pedal or applies the brake pedal. This is shown to cause oscillations in the pedal input and powertrain torque when a conventional driver model is adopted. Look-ahead information, together with other predicted vehicle states, are adopted to control the vehicle speed, in particular, during deceleration, and to improve the driver model so that oscillations can be avoided. The improved driver model makes analysis and validation of the control strategy for an integrated starter generator (ISG) hybrid powertrain possible.     

制动与转向协调动作的车辆避撞控制研究（双语出版）

为了弥补现有汽车避撞控制策略以及碰撞风险评价指标单一的不足，提出转向和制动协调的主动避撞控制系统。首先规划了五次多项式换道路径，在对其理论分析的基础上得到转向临界避撞距离和与目标车道车辆的安全距离约束。其次，考虑道路附着系数和系统延迟的影响，基于制动过程给出制动临界避撞距离，并以纵向行驶安全系数ξ和碰撞时间倒数T^-1_TC划分安全行驶区域，利用驾驶人实车跟车数据标定稳态跟随/定速巡航区域的阈值。随后，通过转向/制动临界避撞距离的对比给出2种避撞方式的安全收益范围。最后搭建Simulink/CarSim联合仿真模型，并对其进行不同初始条件下的避撞仿真试验。研究结果表明：转向操作在制动距离不足时仍是有效的；当主车高速近距离接近静止前车时，主车可以顺利采取转向换道动作，而常规ACC系统在2.5 s处的车间相对距离为-0.76 m，事实上已经发生了碰撞；当相邻车道前车与主车纵向间距不满足换道安全距离约束时，避撞控制系统进入紧急制动模式，最大制动减速度达到-0.8g（g为重力加速度），实际最小车间距为5.1 m；通过转向和制动的协调动作，充分发挥了车辆的避撞潜力；ξ和T^-1_TC指标的融合，可以更好地评估碰撞风险并实现不同控制模式的转换，在保证行车安全的同时可避免过分制动给乘客造成的紧张感。     

汽车防误踩加速踏板系统的研发

为减少和防止紧急制动时误踩加速踏板此类事故的发生,利用汽车加速操作和紧急制动操作存在可分辨的角速度和角加速度的差别,设计了防误踩加速踏板系统,并对系统进行了台架试验和实车测试。结果表明,该系统缩短了汽车的制动距离,有效地防止误踩事故的发生,极大地提高了行车的主动安全性。     

排气设计对制动性能的影响分析

评价整车制动性能的指标包括制动距离、制动减速度、制动抗热衰退性和制动稳定性等.制动系统中的每一项参数达标与否都会对上述指标产生影响,如制动卡钳的排气设计不佳,管路空气未排尽,由于空气的压缩率较大,在实施制动时空气被压缩,制动液传递压力的效果降低,导致制动疲软等问题.本文以制动系统的排气设计为例,分析出制动机构中的卡钳导...     

车路协同无信号交叉口的矩形冲突检测及消解

针对车路协同环境下的冲突问题，建立了以系统反应时间代替驾驶员反应时间的自动驾驶车辆制动距离模型，以此作为安全距离改进了矩形冲突检测模型，并根据轨迹优化的研究思路，提出了以矩形冲突检测模型为基础的冲突消解算法，对非通行优先权车辆进行速度引导，避免车辆冲突。在车联网开源框架 Veins 的基础上，将交通仿真器 SUMO和网络仿真器 OMNeT++双向耦合，并对冲突检测模型与消解模型进行验证。仿真结果显示，该冲突检测及消解模型具有可行性，与传统无信号交叉口四路停车让行规则相比，模型中的速度引导方案能减少合流冲突车辆 8.6%的平均行驶时间，减少交叉冲突车辆 8.3%的平均行驶时间；合流冲突和交叉冲突中车辆的平均速度分别提高了61.4%和105.0%。在实际应用中，冲突消解模型可以为不同速度范围内的自动驾驶车辆提供速度参考，降低无信号交叉口车辆发生碰撞的概率，提高无信号交叉口的通行效率。     

Evaluation of preview G-Vectoring control to decelerate a vehicle prior to entry into a curve

This paper describes the development of the braking assistance system based on a “G-Vectoring” concept. The present work focuses in particular on “Preview G-Vectoring Control” (PGVC), which is based on the “G-Vectoring Control” (GVC) scheme. In GVC, the longitudinal-acceleration control algorithm is based on the actual lateral jerk. PGVC decelerates a vehicle before it enters a curve, and is based on a new longitudinal-acceleration control algorithm which uses predicted and actual lateral jerk. Using the predicted lateral jerk makes it possible to decelerate the vehicle prior to curve entry. This deceleration can emulate a driver’s deceleration as the vehicle approaches a curve entry. PGVC is based on such deceleration algorithms and enables automatic deceleration similar to the action of a driver. It is thus possible to significantly improve the driver’s feeling when this system is activated. Driving tests with this new control system on snowy-winding course confirmed that the automatic brake control quality improved considerably compared to manual driver control considering both lap time and ride quality. These results indicate that PGVC can be a useful braking assistance system not only to improve the driver’s handling performance but also to reduce the brake-task during driving on winding roads.     

汽车防抱死制动系统的自抗扰控制研究

汽车防抱死制动系统(Anti-lock Braking System,ABS)的作用是确保汽车制动时行驶方向的稳定性、可靠性,但是目前仍存在非线性、时变性以及参数不确定性等问题.为保证汽车制动行驶过程中的操纵稳定性和安全性,进一步实现各工况下防抱死制动系统的优化控制,以影响整车稳定的变量滑移率为研究对象,分析所设计策略...     

Braking Force Distribution Control for Improved Vehicle Dynamics and Brake Performance

This paper describes the feasibility of improving the braking performance of a commercial vehicle by using an electronic braking system. An electronic braking system enables the braking force at each wheel to be independently controlled. Braking force distribution control makes the braking force at each wheel proportional to each wheel's load. Results of computer simulation and vehicle test showed that the proposed control laws can eliminate the effects of a laden condition on the braking distance and can increase the degree of deceleration at which wheel lock occurs, resulting in improved vehicle attitude stability during a critical maneuver.     

Emergency Braking Control with an Observer-based Dynamic Tire/Road Friction Model and Wheel Angular Velocity Measurement

Summary A control scheme for emergency braking of vehicles is designed. The tire/road friction is described by a LuGre dynamic friction model. The control system output is the pressure in the master cylinder of the brake system. The controller utilizes estimated states for a feedback control law that achieves a near maximum deceleration. The state observer is designed using linear matrix inequality (LMI) techniques. The analysis shows that using the wheel angular speed information exclusively is not sufficient to rapidly estimate the velocity and relative velocity, due to the fact that the dynamical system is almost unobservable with this measurement as output. Findings are confirmed by simulation results that show that the estimated vehicle velocity and relative velocity converge slowly to their true values, even though the internal friction state and friction parameters converge quickly. The proposed control system has two main advantages when compared with an antilock braking system (ABS): (1) it produces a source of a priori information regarding safe spacing between vehicles that can be used to increase safety levels in the highway; and (2) it achieves a near optimal braking strategy with less chattering.     

Braking Force Distribution Control for Improved Vehicle Dynamics and Brake Performance

SUMMARY

This paper describes the feasibility of improving the braking performance of a commercial vehicle by using an electronic braking system. An electronic braking system enables the braking force at each wheel to be independently controlled. Braking force distribution control makes the braking force at each wheel proportional to each wheel's load. Results of computer simulation and vehicle test showed that the proposed control laws can eliminate the effects of a laden condition on the braking distance and can increase the degree of deceleration at which wheel lock occurs, resulting in improved vehicle attitude stability during a critical maneuver.     

Emergency Braking Control with an Observer-based Dynamic Tire/Road Friction Model and Wheel Angular Velocity Measurement

Summary A control scheme for emergency braking of vehicles is designed. The tire/road friction is described by a LuGre dynamic friction model. The control system output is the pressure in the master cylinder of the brake system. The controller utilizes estimated states for a feedback control law that achieves a near maximum deceleration. The state observer is designed using linear matrix inequality (LMI) techniques. The analysis shows that using the wheel angular speed information exclusively is not sufficient to rapidly estimate the velocity and relative velocity, due to the fact that the dynamical system is almost unobservable with this measurement as output. Findings are confirmed by simulation results that show that the estimated vehicle velocity and relative velocity converge slowly to their true values, even though the internal friction state and friction parameters converge quickly. The proposed control system has two main advantages when compared with an antilock braking system (ABS): (1) it produces a source of a priori information regarding safe spacing between vehicles that can be used to increase safety levels in the highway; and (2) it achieves a near optimal braking strategy with less chattering.     

新能源汽车制动系统的发展趋势

伴随着新能源汽车的快速发展,使得越来越多的人员开始关注新能源汽车技术的提升。其中,制动系统作为保障汽车安全运行的主要系统之一,其利用制动器与车轮的摩擦来强制性控制行驶中的汽车达成减速或者停车的目的。制动系统在汽车行驶期间同样起到了保持汽车速度稳定、在各种道路状态下保持汽车停车时稳定不动的作用。而在本文当中,则主要针对新能源汽车制动系统的发展趋势展开了探讨与分析。     

Utilisation of optimisation solutions to control active suspension for decreased braking distance

This work deals with how to utilise active suspension on individual vehicle wheels in order to improve the vehicle performance during straight-line braking. Through numerical optimisation, solutions have been found as regards how active suspension should be controlled and coordinated with friction brakes to shorten the braking distance. The results show that, for the studied vehicle, the braking distance can be shortened by more than 1?m when braking from 100?km/h. The applicability of these results is studied by investigating the approach for different vehicle speeds and actuator stroke limitations. It is shown that substantial improvements in the braking distance can also be found for lower velocities, and that the actuator strokes are an important parameter. To investigate the potential of implementing these findings in a real vehicle, a validated detailed vehicle model equipped with active struts is analysed. Simplified control laws, appropriate for on-board implementation and based on knowledge of the optimised solution, are proposed and evaluated. The results show that substantial improvements of the braking ability, and thus safety, can be made using this simplified approach. Particle model simulations have been made to explain the underlying physical mechanisms and limitations of the approach. These results provide valuable guidance on how active suspension can be used to achieve significant improvements in vehicle performance with reasonable complexity and energy consumption.     

关于汽车制动系统性能分析及优化设计探讨

我国汽车产业发展的速度在不断的加快,同时得到了我国有关部门的重视,在这种情况下,汽车产业的安全问题也是人们非常重视的问题.在汽车的安全系统中,汽车制动系统是非常关键的作用.汽车制动系统的主要作用是要确保车辆在进行制动的过程中有比较稳定的减速过程.本文对汽车制动系统的性能进行了深入的分析,并提出相应的优化设计.     

汽车紧急制动响应的分析

汽车紧急制动时,制动力矩、制动减速度、车速、车体俯倾角及其角加速度与时间呈非线性关系。本文对BJ212轻型越野汽车满载紧急制动进行了试验,以试验结果为依据,讨论了汽车紧急制动时诸参数之间的关系。其结论是:在瞬变过程中,制动减速度及车体俯倾角加速度与其制动初速度无关;在平稳过程中,制动减速度及车体俯倾角加速度随制动初速度增大而减小,而且大致成线性关系。