转向加速工况下汽车驱动防滑控制系统滑转率算法研究

汽车低速转弯加速时,用后轮轮速作为参考车速计算驱动轮滑转率会造成计算偏差,引起驱动防滑控制系统误干预,为此提出了驱动轮滑转率计算的修正算法.该修正算法不需要增加前轮转角传感器,而是采用两非驱动轮轮速估计车身横摆角速度和汽车前轮转角,进而计算出前轮参考轮速,并将前轮参考轮速代替车速对转弯工况的驱动轮滑转率计算进行修正.试验结果表明,该修正算法消除了滑转率计算误差,可防止汽车在高附着路面上转弯加速时驱动防滑控制系统的误干预.     

四轮独立驱动电动汽车多模式自适应车速估计方法

提出一种多模式自适应车速在线估计方法,通过轮速、车辆加速度等信息综合判断每个车轮的稳定性,利用Simulink/Stateflow搭建逻辑决策模型,根据四轮稳定状态实时选择相应策略对车速进行在线估计,同时研究了轮加速度与车辆加速度的内在联系,并根据仿真结果推导了经验关系式。在Simulink/CarSim联合仿真环境下进行工况仿真,并基于dSPACE/Infineon-TriCore搭建试验平台,开展硬件在环试验,结果表明,该方法可以较为精确地对车速进行实时估计。     

ABS/TCS/AYC中参考车速和滑移率算法研究

文中充分利用了稳定性控制系统中的各传感器信号,提出了ABS/TCS/AYC 3种工作模式下计算参考车速和滑移率的算法.ABS工作模式下,利用主缸压力传感器信号估算车辆减速度,提高参考车速计算精度;TCS工作模式下,提出了参考轮速的概念用于转向工况;AYC工作模式下,选择合适的车轮作为基准轮,利用横摆及转向盘转角信号分别计算各轮的参考轮速而求出滑移率.试验证明这种算法提高了3种工作模式下参考车速和滑移率的计算精度,避免了系统的误干预.     

三轴车辆全轮转向最优控制EI北大核心CSCD

为提高三轴车辆在正常行驶工况下的操纵稳定性,综合考虑车辆的低速和高速转向性能,提出了三轴车辆全轮转向最优控制策略。建立了三轴全轮转向车辆的线性2自由度模型,分别制定了车辆低速和高速时的控制目标并建立了相应的理想模型,应用线性二次型最优控制中的状态调节器理论,采用前馈加状态反馈跟踪理想模型的控制方法设计了全轮转向最优控制系统,最后利用MATLAB/Simulink建立了控制系统仿真模型,对控制系统在不同车速下的控制性能进行了仿真。结果表明,全轮转向最优控制方法低速时可使车辆具有所在车速下的最小转弯半径,高速时在改善车辆稳定性的同时不增加驾驶员的操作负担。     

全驱车型车速检测误差分析

基于对全轮驱动车辆传动系和检测线实际条件的分析,分析了车速误差的原因,制定了可实施的全轮驱动车辆车速检测方案,应用于检测实践中。     

一种基于加速度及轮速信息的参考车速估计方法

以两轮驱动轿车为研究对象,提出了一种基于加速度及轮速信息的参考车速估计方法。以Kalman滤波为基本算法,结合试验分析,通过估计系统噪声特征和修正量测方程,改进了算法对加速度量测信号静态偏差变化的跟踪能力,提高了参考车速的估计精度。利用该方法估计参考车速具有不依赖大量试验、计算量小的特点,适于实车应用。     

基于自适应卡尔曼滤波的轮速信号处理技术

分析了轮速信号的检测误差,建立了轮速估计的系统状态空间模型,采用了用于轮速估计的自适应卡尔曼滤波算法.利用MATLAB进行了仿真,验证了算法的有效性.实车试验表明,滤波后的轮速信号延时小,响应速度快,平滑效果比较理想,可以用来直接估计车速.     

高速工况下间接式胎压监测的影响因素研究与优化

为解决间接式胎压监测在车辆高速工况下性能波动的问题,通过车辆行驶动力学分析发现波动的主要因素为空气阻力,基于刷子轮胎模型对轮胎纵向力和滑转率进行建模,建立了胎压监测参数随车速变化的轮速信号补偿方程。采用CarSim和Simulink进行联合仿真,通过实车采样数据求解补偿方程的待定系数并计算高速工况下的信号补偿量,同实测数据进行对比,实际预测效果满足要求,提出的方法可以对高速工况下间接式胎压监测完成补偿。     

测功机在大型车辆动力性能检测中的应用

针对大型车辆的动力性能检测,首先介绍汽车动力性能检测方法,包括驱动轮输出功率检测、驱动轮轮边稳定车速检测及判定方法;然后介绍三轴六筒测功机原理,并以大型车辆进行现场测试,得到实时检测数据,验证检测方法的有效性。结果表明:轮边稳定车速60.8km/h,大于额定车速57.9km/h;且在额定车速下发动机功率为203.4kW,小于该车型发动机额定功率248kW,检测结果符合车辆动力性能检测标准。     

ABS轮速信号的采集方法研究

在分析现有轮速信号采集方法的基础上,提出了一种能够将精度和实时性相结合的速度测量方法--自适应的轮速信号采集方法.该方法可根据轮速大小采用变化的采样周期采集轮速信号.通过仿真和路试结果表明,该自适应轮速信号采集方法在全车速范围内均能满足采集精度与实时性要求.     

基于变传动比的全轮线控转向车辆可拓H∞控制方法研究

为了解决传统固定转向传动比以及鲁棒H_∞控制方法无法很好地改善车辆稳定性的问题,提出全轮线控转向车辆的变传动比和可拓H_∞控制策略。首先,建立八自由度车辆动力学模型和轮胎模型。其次,以车辆方向盘转角和车速为输入信息,基于模糊控制方法设计全轮线控转向车辆的转向传动比,并计算出全轮线控转向车辆的前轮转角。然后,以横摆角速度偏差和偏差微分为特征值,基于可拓控制理论将车辆状态划分为3个区域：经典域、可拓域和非域;在经典域中,采用基于横摆角速度反馈的鲁棒H_∞控制方法,实时获取全轮线控转向车辆的后轮转角;在可拓域和非域中,结合可拓控制和H_∞控制策略,动态调整H_∞控制器的输出信号,在保证控制系统鲁棒性的前提下改善车辆的操纵稳定性。最后,基于MATLAB/Simulink仿真平台和自主研制的全轮线控转向特种消防救援车辆,通过正弦转向、单移线、阶跃转向、双移线等典型工况对所提控制方法进行验证,并以平均绝对误差和均方根误差为评价指标,与无控制和H_∞控制方法进行对比分析。仿真和试验测试结果表明：①变传动比控制方法不仅可以提高车辆低速时的转向灵敏度,也能改善车辆高速时的稳定性;②相比传统鲁棒H_∞控制,可拓H_∞控制策略提高了全轮线控转向车辆的操纵稳定性,改善了车辆全轮线控转向控制系统的鲁棒性。     

Distributed and self-adaptive vehicle speed estimation in the composite braking case for four-wheel drive hybrid electric car

Considering the controllability and observability of the braking torques of the hub motor, Integrated Starter Generator (ISG), and hydraulic brake for four-wheel drive (4WD) hybrid electric cars, a distributed and self-adaptive vehicle speed estimation algorithm for different braking situations has been proposed by fully utilising the Electronic Stability Program (ESP) sensor signals and multiple powersource signals. Firstly, the simulation platform of a 4WD hybrid electric car was established, which integrates an electronic-hydraulic composited braking system model and its control strategy, a nonlinear seven degrees-of-freedom vehicle dynamics model, and the Burckhardt tyre model. Secondly, combining the braking torque signals with the ESP signals, self-adaptive unscented Kalman sub-filter and main-filter adaptable to the observation noise were, respectively, designed. Thirdly, the fusion rules for the sub-filters and master filter were proposed herein, and the estimation results were compared with the simulated value of a real vehicle speed. Finally, based on the hardware in-the-loop platform and by picking up the regenerative motor torque signals and wheel cylinder pressure signals, the proposed speed estimation algorithm was tested under the case of moderate braking on the highly adhesive road, and the case of Antilock Braking System (ABS) action on the slippery road, as well as the case of ABS action on the icy road. Test results show that the presented vehicle speed estimation algorithm has not only a high precision but also a strong adaptability in the composite braking case.     

Engine clutch torque estimation for parallel-type hybrid electric vehicles

This paper mainly focuses on the accurate estimation of the torque transferred through the engine clutch installed between the engine and the drive motor in parallel-type hybrid electric vehicles. The estimation of the engine clutch torque primarily relies on the forward-direction observer which uses the nominal engine net torque information. To overcome the limitation of using the nominal engine torque information that it may not be accurate during the transient states or due to the influence of external disturbance such as the road condition and wind, the forward-direction observer is supplemented by the use of reverse-direction observer which uses the driveline model and wheel speed measurements. In addition, the drive motor torque information is used to calibrate the nominal engine torque during the idle charging state, so that the driveline characteristic unique to parallel-type hybrid electric vehicle can be utilized to increase the estimation accuracy. Finally, the estimation performance of the designed observer is tested via simulation and experiments based on a real vehicle.     

4WD汽车应用粘性联轴器分析

粘性联轴器这一新装置以其独有的特性在四轮驱动汽车上得到广泛应用，粘性联轴器一经确定结构，即可通过转速差自动调节传递转矩的特性，分析了四轮驱动汽车采用粘性联轴器的可能性，介绍了采用粘性联轴器连接的四轮驱动形式和工作原理，阐述了汽车速度，轮胎滑移率对粘性联轴器转速差的影响。     

Model-Based Road Friction Estimation

The tire/road friction coefficient, μ, has a significant role in vehicle longitudinal and lateral control, and there has been associated efforts to measure or estimate the road surface condition to provide additional information for stability augmentation systems of automobiles. In this paper, a model based road friction estimation algorithm is proposed from easily measured signals such as yaw rate and wheel speed. For the development of the estimator, a low order vehicle model incorporated with simple but effective tire model. Field tests of the estimator using actual vehicle measurements show promising results.     

Experimental investigations on continuous regenerative anti-lock braking system of full electric vehicle

Functions of anti-lock braking for full electric vehicles (EV) with individually controlled wheel drive can be realized through conventional brake system actuating friction brakes and regenerative brake system actuating electric motors. To analyze advantages and limitations of both variants of anti-lock braking systems (ABS), the presented study introduces results of experimental investigations obtained from proving ground tests of all-wheel drive EV. The brake performance is assessed for three different configurations: hydraulic ABS; regenerative ABS only on the front axle; blended hydraulic and regenerative ABS on the front axle and hydraulic ABS on the rear axle. The hydraulic ABS is based on a rule-based controller, and the continuous regenerative ABS uses the gain-scheduled proportional-integral direct slip control with feedforward and feedback control parts. The results of tests on low-friction road surface demonstrated that all the ABS configurations guarantee considerable reduction of the brake distance compared to the vehicle without ABS. In addition, braking manoeuvres with the regenerative ABS are characterized by accurate tracking of the reference wheel slip that results in less oscillatory time profile of the vehicle deceleration and, as consequence, in better driving comfort. The results of the presented experimental investigations can be used in the process of selection of ABS architecture for upcoming generations of full electric vehicles with individual wheel drive.     

Lateral handling improvement with dynamic curvature control for an independent rear wheel drive EV

The integrated longitudinal and lateral dynamic motion control is important for four wheel independent drive (4WID) electric vehicles. Under critical driving conditions, direct yaw moment control (DYC) has been proved as effective for vehicle handling stability and maneuverability by implementing optimized torque distribution of each wheel, especially with independent wheel drive electric vehicles. The intended vehicle path upon driver steering input is heavily depending on the instantaneous vehicle speed, body side slip and yaw rate of a vehicle, which can directly affect the steering effort of driver. In this paper, we propose a dynamic curvature controller (DCC) by applying a the dynamic curvature of the path, derived from vehicle dynamic state variables; yaw rate, side slip angle, and speed of a vehicle. The proposed controller, combined with DYC and wheel longitudinal slip control, is to utilize the dynamic curvature as a target control parameter for a feedback, avoiding estimating the vehicle side-slip angle. The effectiveness of the proposed controller, in view of stability and improved handling, has been validated with numerical simulations and a series of experiments during cornering engaging a disturbance torque driven by two rear independent in-wheel motors of a 4WD micro electric vehicle.     

基于稳定性和宏观交通流模型的车辆路径规划

为了提升车辆的安全性和能量利用率,从路径规划的层面出发,针对避免车辆遇到极端工况及低效率工况的问题,提出将车辆稳定性判据模型和交通流模型相结合的方法来规划车辆路径,使得车辆在路面湿滑情况下实现快速、安全的行驶。使用交通流模型预测车辆未来将要面临的交通环境变化,再使用稳定性判据模型评估未来交通的安全性,以便为混合动力车辆规划出最快且最安全的路径。具体来讲,为了预测混合动力车辆未来将要面临的车速及车流密度的变化,使用通量矢量分裂格式求解广义Aw-Rascle-Zhang（GARZ）宏观交通流模型。此外,使用驾驶人在环仿真平台PreScan,收集了同一驾驶人在不同车速及不同相对前车距离时给出的前轮转向角响应。基于前轮驱动（FWD）前轮转向（FWS）车辆和全轮转向（AWS）分布式驱动车辆（DDV）的Simulink模型,给出了不同前轮转向角对应的轮胎力饱和因子（δ_TFSC）响应。使用人工神经网络训练不同车速和车流密度对应的δ_TFSC,建立了车辆的稳定性判据模型。使用新建立的稳定性判据模型对交通流模型预测的参数（车流速及车流密度）进行稳定性评估。然后,基于以上的方法优化了车辆行驶路径,以确保车辆在湿滑路面上的行驶安全。最后,使用US-101真实交通流数据来验证交通流模型的预测结果。经实例验证得出：交通流模型与车辆横向稳定性判据模型相结合可以从路径规划的层面保证车辆安全行驶并提升交通系统的通行效率。