电子稳定程序(ESP)(六)

五、适合于制动和传动系统的行车安全系统 1．防抱制动系统(ABS)(1)研究课题在湿滑路面行驶或是驾驶员猛踩制动(由于突然出现意想不到的障碍物或是其他驾驶员的错误)等危机情况，在没有ABS的情况下，车轮在制动时就容易抱死，车辆便不能控制转向，引起打滑。更严重的是偏离道路。在这种情况下，ABS防止车轮抱死．保持其制动时的转向性，从而有效降低打滑。(见图13)     

汽车防抱制动系统的现状及发展趋势

汽车防抱制动系统(简尔 ABS)是最近几年开发使用的一种提高汽车制动安全性的高新技术装置。当汽车在行驶中进行制动时,尤其是在潮湿、泥泞、冰雪路面等低附着系数路面上高速行驶中实施紧急制动,车轮很容易抱死拖滑,一旦有一个以上车轮抱死,就会造成车辆侧滑甩尾,方向失控,导致车辆相撞倾覆,甚至造成车毁人亡的严重事故。ABS 就是针对这一问题而开发的汽车安全性装置。     

汽车ABS使用须知

ABS称为“防抱死”系统。虽然现代的ABS系统可最大限度地提高制动时车辆的稳定性．但不能防止车轮在所有的情．况下都不发生滑移。在积雪结冰或湿滑的路面上行驶上时，汽车稳定性仍是较差的。在此路面行驶时应减慢车速，小心驾驶。     

后驱电制动对ABS触发表现的影响

汽车行驶过程中,在紧急制动和路面湿滑情况下,踩下制动踏板会触发ABS功能,ABS主要作用为控制车轮的滑移率,防止制动过程中车轮发生抱死甩尾.ABS性能的优劣主要通过制动性能测试完成,包括高附路面、低附路面、对开路面、对接路面及绕圆等工况.用户在普通工况下较少触发ABS,所以对ABS误触发、频触发抱怨比较大.重点说明后驱电制动对ABS触发表现的影响.     

使用与检修ABS系统应注意的问题

汽车防抱死制动系统(Anti-LockBrakreSysterm)，简称ABS。它是汽车上的一种主动安全装置，其作用是在汽车制动时，防止车轮抱死在路面上滑拖，以提高汽车制动过程中的方向稳定性、转向控制能力和缩短制动距离。使汽车制动更为安全有效。但是如果使用不当或检修方法不正确，将会导至ABS系统效能降低或丧失。以至发生车辆事故。因此，在使用与检修过程中应注意以下几点问题：     

逻辑门限值的汽车ABS构建与仿真分析

本文采用基于逻辑门限值的ABS控制方法,研究如何提升汽车在湿滑等复杂路面的制动性能。首先建立了单轮汽车系统动力学模型、轮胎模型、制动系统模型等,将汽车滑移率控制在0.17~0.2范围内,在Simulink中搭建制动系统的ABS控制仿真模型并进行离线仿真;仿真结果表明:采用逻辑门限值ABS控制方法可使制动距离减少12.5%,制动时间缩短6.25%,同时可将滑移率控制在最佳滑移率附近,对于提升汽车的制动性能和行驶安全性能有很大帮助。     

汽车防抱死系统的使用和维护

装用ABS的汽车制动时，不仅可使车辆获得较高的制动力，也可使车辆有较好的侧向稳定性和操纵稳定性，从而使驾驶员的制动操作更方便，特别是在湿滑道路上行驶制动时，驾驶员可不必使用点制动的方法来保证汽车的方向稳定性。也就是说汽车装用ABS后，驾驶员只要踩下制动踏板，ABS就可对汽车实施有效制动，制动操作更为简化。     

汽车防抱系系统的使用和维护

装用ABS的汽车制动时，不仅可使车辆获得较高的制动力，也可使车辆有较好的侧向稳定性和操纵稳定性，从而使驾驶员的制动操作更方便，特别是在湿滑道路上行驶制动时，驾驶员可不必使用点制动的方法来保证汽车的方向稳定性。也就是说汽车装用ABS后，驾驶员只要踩下制动踏板，ABS就可对汽车实施有效制动，制动操作更为简化。     

事故ABS车辆典型制动故障分析

从两起装备有ABS事故车辆典型案例入手,分析了该类车辆典型制动故障的产生原因;对装备ABS系统的汽车在转弯行驶制动时的操纵稳定性进行了仿真分析,并提出了ABS车辆行驶中在行驶环境和道路条件等因素发生变化时应注意的问题。     

驾车时容易犯的错误有哪些？

有ABS就放心开快车：有时ABS的制动距离较一般制动系统汽车的制动距离要长，在不好的路面如湿滑路面、粗糙的砂砾路就可能造成危险。电喷车起动急踩油门电喷车型起动日寸，没有必要踩油门，更没有必要在起动前连续急踩，否则反而会造成发动机起动不良。     

汽车ABS中的模糊神经网络模型参考自适应控制策略

针对汽车制动的特点以及汽车防抱死制动系统的性能要求,建立了汽车的数学模型,提出一种模糊神经网络的自适应控制方案,构建了基于模糊神经网络的控制器和辨识器的结构模型。通过对网络参数的离线训练得出其初值,在控制过程中对网络参数进行在线微调,实现对汽车制动过程的有效控制。仿真结果表明:在不同的路面,汽车均能保持在最佳滑移率附近进行制动,制动时间及距离比较理想,满足ABS的安全性能要求。     

基于视觉识别的线控制动压力滑模控制

制动安全是车辆主动安全的关键技术之一。制动决策和执行器控制是影响线控制动系统性能的两个主要因素。路面自适应性和控制器鲁棒性分别对制动决策和执行器控制有着重要影响,制约着线控制动系统的发展。本文中以一种液压调控的线控制动系统为基础,针对路面自适应性和控制器鲁棒性问题,提出一种双层结构的制动系统控制器,上层采用计算机视觉的方法对路面类型进行识别,根据识别结果制定当前路面的最佳滑移率;下层针对制动系统参数不确定性问题,引入滑模控制理论对制动过程中的最佳滑移率进行跟踪控制。通过仿真与实验验证,结果表明,双层结构的制动系统控制器相比传统控制器,路面的自适应性好,制动距离更短,控制器鲁棒性好。     

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.     

汽车电子防抱制动系统仿真的研究

本文分析了汽车车轮制动瞬态动力学，结合精确的１５自由度空间刚体动力学模型，定量地分析了车轮抱死松开所获得的加减速度值，并为防抱制动提供了准确的加减速度阈值，同时考虑到防抱制动系统本身装置的特性，提出了最佳又符合实际的制动矩控制参数，使用仿真结果更接近实际，为电子防抱制动系统的研究提供较完整的理论体系和分析方法，并开发了汽车电子防抱制动系统模型（ＨＶＯＳＭ－ＡＢＳ）及模拟程序，该程序具有１６种不同的     

Optimisation of active suspension control inputs for improved performance of active safety systems

A collocation-type control variable optimisation method is used to investigate the extent to which the fully active suspension (FAS) can be applied to improve the vehicle electronic stability control (ESC) performance and reduce the braking distance. First, the optimisation approach is applied to the scenario of vehicle stabilisation during the sine-with-dwell manoeuvre. The results are used to provide insights into different FAS control mechanisms for vehicle performance improvements related to responsiveness and yaw rate error reduction indices. The FAS control performance is compared to performances of the standard ESC system, optimal active brake system and combined FAS and ESC configuration. Second, the optimisation approach is employed to the task of FAS-based braking distance reduction for straight-line vehicle motion. Here, the scenarios of uniform and longitudinally or laterally non-uniform tyre–road friction coefficient are considered. The influences of limited anti-lock braking system (ABS) actuator bandwidth and limit-cycle ABS behaviour are also analysed. The optimisation results indicate that the FAS can provide competitive stabilisation performance and improved agility when compared to the ESC system, and that it can reduce the braking distance by up to 5% for distinctively non-uniform friction conditions.     

Modeling and control of an anti-lock brake and steering system for cooperative control on split-mu surfaces

The brake and steering systems in vehicles are the most effective actuators that directly affect the vehicle dynamics. In general, the brake system affects the longitudinal dynamics and the steering system affects the lateral dynamics; however, their effects are coupled when the vehicle is braking on a non-homogenous surface, such as a split-mu road. The yaw moment compensation of the steering control on a split-mu road is one of the basic functions of integrated or coordinated chassis control systems and has been demonstrated by several chassis suppliers. However, the disturbance yaw moment is generally compensated for using the yaw rate feedback or using wheel brake pressure measurement. Access to the wheel brake pressure through physical sensors is not cost effective; therefore, we modeled the hydraulic brake system to avoid using physical sensors and to estimate the brake pressure. The steering angle controller was designed to mitigate the non-symmetric braking force effect and to stabilize the yaw rate dynamics of the vehicle. An H-infinity design synthesis was used to take the system model and the estimation errors into account, and the designed controller was evaluated using vehicle tests.     

A practical identifier design of road variations for anti-lock brake system

Emergency brake technologies have always been a major interest of vehicle active safety-related studies. On homogeneous surfaces, traditional anti-lock brake system (ABS) can achieve efficient braking performance and maintain the handling capability as well. However, when road conditions are time variant during the braking process, or different at the bilateral wheels, braking stability performance is likely to be degraded. To address this problem and enhance ABS performances, a practical identifier of road variations is developed in this study. The proposed identifier adopts a statechart-based approach and is hierarchically constructed with a wheel layer and a full vehicle layer identifier. Based on the identification results, modifications are made to a four-phase wheel-behaviour-based ABS controller to enhance its performance. The feasibility and effectiveness of the proposed identifier in collaborating with the modified ABS controller are examined via simulations and further validated by track tests under various practical braking scenarios.     

Improvement of drivability and fuel economy with a hybrid antiskid braking system in hybrid electric vehicles

When braking on wet roads, Antilock Braking System (ABS) control can be triggered because the available brake torque is not sufficient. When the ABS system is active, for a hybrid electric vehicle, the regenerative brake is switched off to safeguard the normal ABS function. When the ABS control is terminated, it would be favorable to reactivate the regenerative brake. However, recurring cycles from ABS to motor regenerative braking could occur. This condition is felt to be unpleasant by the driver and has adverse effects on driving stability. In this paper, a novel hybrid antiskid braking system using fuzzy logic is proposed for a hybrid electric vehicle that has a regenerative braking system operatively connected to an electric traction motor and a separate hydraulic braking system. This control strategy and the method for coordination between regenerative and hydraulic braking are developed. The motor regenerative braking controller is designed. Control of regenerative and hydraulic braking force distribution is investigated. The simulation and experimental results show that vehicle braking performance and fuel economy can be improved and the proposed control strategy and method are effective and robust.     

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,分析所设计策略的控制效果。搭建汽车动力学模型、制动系统模型、轮胎模型和滑移率模型等主要模型,设计基于滑移率的ABS二阶非线性自抗扰控制器。运用MATLAB/Simulink软件对基于自抗扰控制（Active Disturbance Rejection Control,ADRC）的ABS制动过程和基于模糊PID控制的ABS制动过程进行仿真,对比研究最佳滑移率、载荷、水泥-冰对接路面、扰动等对制动过程中的轮速、车速以及滑移率等动态性征反映的稳定性和抗扰能力的影响,同时研究其对最终制动距离和最终制动时间反映的制动性能的影响。最后,将自抗扰控制器和模糊PID控制器装配于试验车辆的ABS,进行水泥路面和冰-水泥对接路面制动过程的实车试验。研究结果表明：基于二阶非线性自抗扰控制算法的ABS制动的最终制动距离和最终制动时间更短、制动效果更优,制动过程中的轮速、车速和滑移率在响应速度、稳定性和抗扰能力等方面均更佳;试验结果与仿真结果吻合,证明了仿真模型及其仿真结果的可行性和正确性。     

分布式驱动电动汽车回馈制动失效的液压补偿控制

分布式驱动电动汽车各驱动轮转速和转矩可以单独精确控制，便于实现整车动力学控制和制动能量回馈，从而提升车辆的主动安全性和行驶经济性。但车辆在回馈制动过程中，一旦1台电机突发故障，其他电机产生的制动力矩将对整车形成附加横摆力矩，从而造成车辆失稳，此时虽可通过截断异侧对应电机制动力矩输出来保证行驶方向，但会使车辆制动力大幅衰减或丧失，同样不利于行车安全。为了解决此问题，提出并验证一种基于电动助力液压制动系统的制动压力补偿控制方法，力图有效保证整车制动安全性。以轮毂电机驱动汽车为例，首先建立了整车动力学模型以及轮毂电机模型，通过仿真验证了回馈制动失效的整车失稳特性以及电机转矩截断控制的不足；然后，建立了电动助力液压制动系统模型，并通过原理样机的台架试验验证了模型的准确性；接着，基于滑模控制算法设计了制动压力补偿控制器，并在单侧电机再生制动失效后的转矩截断控制基础上完成了液压制动补偿控制效果仿真验证；最后，通过实车试验证明了所提控制方法的有效性和实用性。研究结果表明：在分布式驱动电动汽车单侧电机再生制动失效工况下，通过异侧电机转矩截断控制和制动系统的液压主动补偿，能够使车辆快速恢复稳定行驶并满足制动强度需求。