【作者】 房永；

【导师】 初亮；

【作者基本信息】 吉林大学 ， 车辆工程， 2010， 博士

【摘要】 随着国民经济的发展和公路交通的改善,半挂汽车列车以其机动灵活的优点逐渐成为公路运输的主要车型之一,目前国内半挂汽车列车保有量21万辆,年产量2.5万辆。但由于其载重量大、尺寸大、质心高等问题,容易导致侧翻和横向失稳而引发交通事故,造成巨大损失。目前提高汽车列车稳定性主要通过优化车辆结构参数和安装稳定性控制系统两中手段,然而优化车辆参数对稳定性的提升有限,因此研究开发稳定性控制系统已成为各个主机厂的紧迫任务。目前比较成熟的稳定性控制系统主要有侧翻警示系统、侧翻控制系统、电子稳定性控制系统和主动防侧倾控制系统等,一般采用的控制方法有:降低发动机输出扭矩、对选定车轮主动施加制动力、调整左右悬架特性。其中电子稳定性控制系统在制动防抱死系统基础上增加了方向盘转角、侧向加速度、横摆角速度等传感器,并利用车载网络获取发动机、变速器等的控制器信息,实时检测车辆的运行状态,当车辆发生侧翻或横摆失稳时,主动降低发动机的输出扭矩并对选定车轮施加制动力以纠正车辆的失稳运动。论文结合科技部863专项、国际科技合作及省市科技支撑计划重大专项等项目的研究内容与中国第一汽车集团公司技术中心密切合作,根据企业对半挂汽车的技术需求,以三轴半挂汽车列车为研究对象,围绕稳定性控制系统的基础理论和控制算法展开研究。提出了稳定性控制算法的整体结构,开发了整车质量、质心位置、侧倾状态、折叠角、名义横摆角速度等车辆状态的估算算法。提出稳定性控制开始和退出的叛别条件,并根据不同的行驶工况设定不同的门限值,对选定车轮施加不同的压力控制。在Matlab环境下开发半挂汽车列车离线仿真平台和硬件在环试验台,对提出的稳定性控制算法在不同工况下进行离线仿真验证和硬件在环试验验证。论文研究成果为一汽集团半挂汽车列车稳定性控制系统的产品开发奠定了理论基础。全文主要内容包括:1、根据汽车列车的运动学原理,建立二十五自由度三轴半挂汽车列车非线性动力学模型。模型包括子系统动力学模型和整车动力学模型,子系统模型有发动机模型、传动系模型、制动器模型、悬架模型、轮胎模型、第五轮约束模型、车轮垂直载荷模型和辅助计算模型等,整车动力学模型包括牵引车和半挂车运动学模型和操纵稳定性模型。模型能够模拟汽车列车的在不同路面上的制动、转向、加速及组合工况,实现稳定性控制所需的仿真。2、提出了稳定性控制算法整体结构,确定半挂汽车列车稳定性控制系统的控制目标,将稳定性控制分为防侧翻控制和横摆稳定性控制两部分。根据对车辆的侧翻的情形分析,结合当前研究条件确定主要研究工况为转弯侧翻。3、半挂汽车载重量在很大范围内变化,导致车辆参数变动很大,从而影响稳定性控制系统的控制效果,因此对需要各种车辆状态进行估算,然后利用估算值对控制参数进行修正。利用多函数法根据发动机和轮速信号在起步加速工况下估算整车质量;利用空气弹簧气囊中的压力信号估算质心距离各车轴的位置;利用侧向加速度和侧倾角速度信号估算质心高度;利用轮速信号估算车速;利用侧倾角速度、侧向加速度和四自由度侧倾模型设计了状态观测器估算牵引车侧倾角;利用汽车列车三自由度模型和扩展卡尔曼滤波算法估算车辆折叠角;利用二自由度模型估算牵引车名义横摆角速度,用来识别牵引车的不足或过多转向特性。4、根据估算的状态变量和车辆转向特性来识别车辆的稳定状态,确定稳定性控制开始和退出的条件。当车辆有侧翻趋势时首先施加试验制动压力,以判断车轮是否离地,然后根据车辆侧翻趋势的不同和转向工况的的不同设定控制门限值和压力控制算法,对于回转转向的控制,在左右车轮充分接地时采用左右轮同时制动的压力切换策略。5、汽车列车发生横摆失稳时,根据所识别的不足或过多转向特性,降低发动机输出扭矩并采用主动制动的方式对选定的车轮施加制动,纠正车辆的失稳状态,当折叠角过大车辆发生折叠危险时,对其压力控制策略进行调整,进行防折叠控制。横摆稳定性控制过程中如果触发了防侧翻控制,则优先进行防侧翻控制。6、根据车辆动力学模型和控制算法,在Matlab环境下搭建包括车辆模型、控制器模型和用户图形界面的离线仿真平台,并利用此平台在高、中、低不同路面附着情况下进行开环方向盘角阶跃输入、鱼钩转向输入、正弦输入和闭环双移线等工况的仿真,对开发的稳定性控制算法进行验证,仿真结果表明所开发的离线仿真平台能够很好的完成稳定性控制算法的仿真试验,所开发的算法能够很好的防止车辆侧翻和横横摆失稳,提高行驶稳定性。7、在离线仿真平台的基础上,开发了基于Matlab/xPC的硬件在环试验台,试验台包括xPc Target实时运行平台、执行机构、传感器、数据采集及处理系统、硬件台架和仿真软件,其中硬件台架包括操纵台架、牵引车台架和半挂车台架三部分。利用硬件在环试验台对开发的稳定性控制算法在不同路面的多种工况下进行试验,试验结果表明所开发的稳定性控制算法能够在多种工况下抑制车辆侧翻和横摆失稳,提高车辆稳定性。更多还原

【Abstract】 As the improvement of national highway transportation, tractor seimi-trailer has become one of the main vehicles for freight, because of its flexibility and mobility. Stock of tractor semitrailer is 210,000, and volume of production every year is 25,000. Howerver, they tend to rollover or loss of lateral stability, even cause severe traffic accidents and huge loss, with its big load capacity, large size, high center of gravity. There are two ways to improve the stability of the current tactor semitrailer, mainly through optimization of structural parameters or installation of stability control systems, but there is little margin for optimization of vehicle parameters to enhance its stability. So development of stabiliyt control systems becomes an urgent task for OEMs’customers.There are many stability products for tractor semitrailer available on the maket, such as rollover stability advisor (RSA), rollover stability control (RSC), electronic stabibility control system (ESC) and active anti-roll control (ARC). All the stability systems enhance vehicle stablility mainly through reducing the output torque of engine, applying braking pressure on selected wheels, or modifying characteristic of suspensions.ESC is developed based on antilock braking system and equipes a steer wheel angle sensor, a yaw rate sensor, a lateral acceleration sensor, etc. ESC also gets the infromation of engine, transmission and suspension through control area network. With these signals, ESC can detect vehicle state in realtime. When vehicle loses its lateral stabiliy or has the trends of rollover, ESC reduces the output torque of engine and applies brake on selected wheels to modify vehicle state.Combined with signaficant projects of 863 special project and international cooperation of ministry of science and technology and technology support program of Jilin provence, cooperated with Rearch center of FAW, according with the acquirements of FAW, a stability control system for tractor semi-trailer with 3 axles is researched in this dissertation. There are big differences between stability control system for tractor semitrailers and that for passenger cars. The stability control system for tractor semitrailers can be divided into two main parts: antirollvoer control and yaw stability control. An integrated structure of control algrithms is proposed in this dissertation, based on which the algorithms of estimation of vehicle states are designed. The algorithms mainly focus on estimation of vehicle mass, positon of center of gravity, rollover state, articulation angle, nomial yaw rate, and vehicle velocity, etc. The conditions of start and quit of stability control are determined, and the thresholds for different driving conditions are set, then the strategy of pressure control is used to control the pressure of the wheels. An offline simulation platform and a hardware-in-the-loop test bench are developed under the environment of Matlab to validate the stability control algrithms under different driving conditions.The main contents of the dissertaion are:1. According to the kinematic principle of tractor semitrailer, a 25 degree-of -freedom nonlinear dynamic model of triaxial tractor-semitrailer is built. The vehicle model includes the dynamics subsystem models and vehicle dynamics system models. The subsystem models include engine model, transmission model, brake model, suspension model, tire model, fifth wheel constraint model, model for calculation of wheel vertical load and auxiliary compute model. The vehicle dynamic models include tractor and trailer kinematics model and the handling stability model. The tractor semitrailer model can simulate braking, steering, accelerating and combined operating conditions on different roads, and perform the desired simulation for vehicle stability control system.2. An integrated structure of stability control algrithm is proposed. The control target of stability control system for tractor semitrailer is determined. The control system is divided into two parts, which are anti-rollover control and yaw stability control. With the analysis of different conditions of rollover, the rollover caused by steering is selected to study in this dissertaiton.3. As the great fluctuation of vehicle load, lots of vehicle paprameters change with load conditions, which may have some effects on stability control, so, some parameters used must be estimated to modify the control parameters. Multi-function is designed to estimate vehicle mass in which the information of engine and wheel speed under starting acceleration conditon is used. The distances between every axle and center of gravity are calculated using pressure signals of air suspension. Height of center of gravity is estimated using the signals of lateral acceleration and roll rate from lateral acceleration sensor and roll rate sensor available in stability control system. Vehicle velocity is estimated using wheel speed signals. A state observer is designed to estimate tractor roll angle using signals of roll rate lateral acceleration and a 4-DOF roll plane model. Extended Kalman Filter and a 3-DOF vehicle model are used to estimate articulation angle of tractor semitrailer. A 2-DOF linear model is built to calcualte the nominal yaw rate of tractor in order to identify the steering characteristics of the tractor.4. According to the estimated vehicle state parameters and the vehicle steering characteristics, which aim to identify the steady state of the vehicle, to determine the start and exit conditions of stability control. When the vehicle has the trend of rollover, firstly a test brake pressure is applied on the tralier wheels to determine whether the wheels lift off the ground, then, according to the different degree of rollover and the steering conditions, it sets different control thresholds and pressure control algorithms. For the backup steering condition, full wheel brake pressure is applied on left and right wheels while the wheels are fully contacted with ground.5. When loss of yaw stability occurs, in accordance with the identified under-or over steering characteristics, the stability control system reduces the engine output torque and actively applies brakes on the selected wheels, to correct the vehicle instability state. When jackknife risk occurs, the pressure control strategy must be adjusted, and anti-jackknife control must be performed. If it triggers anti-roll control during yaw stability control, anti-rollover control will take the priorty.6. According to the tractror semitrailer dynamics model and control algorithms presented above, an offline simulation platform under Matlab environment is built, and the platform includes vehicle model, controller model and the graphical user interface. With this platform, off-line simulations of steering angle of open loop as step input, fishook input, sinusoidal input and closed-loop as double lane etc. on high, medium and low adhesion coefficient road, are perfomed. The simulation results show that the off-line simulation platform is able to complete the validation of stability control algorithm and the algorithm can prevent vehicle from rollover and loss of lateral stability and the stability control system can enhance driving stability under many conditions.7. Based on the offline simulation platform, a hardware-in the-loop test bentch is developed using the toolbox of Matlab / xPC. The test bentch includes xPc Target real-time platform, actuators, sensors, data acquisition, processing system and simulation software. The hardware of test bentch includes three parts, manipulation bentch, tractor bentch and semitrailer bentch. Tests are perfomed on the test bentch in different road conditions to validate the developed stability control algorithm furtherly. The test results show that the stability of control algorithms developed in the dessertation can prevent vehicle from rollover and yaw instability, and improve vehicle stability in a variety of driving conditions.更多还原