请帮忙翻译成英语在汽车防抱死制动系统出现之前,汽车所用的都是开环制动系统.其特点是制动器制动力矩的大小仅与驾驶员的操纵力、制动力的分配调节以及制动器的尺寸和型式有关.由于没有车轮运动状态的反馈信号,无法测知制动过程中车轮的速度和抱死情况,汽车就不可能据此调节轮缸或气室制动压力的大小.因此在紧急制动时,不可避免地出现车轮在地面上抱死拖滑的现象.当车轮抱死时,地面的侧向附着性能很差,所能提供的侧向附着力很小,汽车在受到任何微小外力的作用下就会出现方向失稳问题,极易发生交通事故.在潮湿路面或冰雪路面上制动时,这种方向失稳的现象会更加严重.汽车防抱死制动系统(Anti-lock Braking System简称ABS)的出现从根本上解决了汽车在制动过程中的车轮抱死问题.它的基本功能就是通过传感器感知车轮每一瞬时的运动状态,并根据其运动状态相应地调节制动器制动力矩的大小以避免出现车轮的抱死现象,因而是一个闭环制动系统.它是电子控制技术在汽车上最有成就的应用项目之一,汽车制动防抱死系统可使汽车在制动时维持方向稳定性和缩短制动距离,有效提高行车的安全性.一、ABS的工作原理汽车制动时由于车轮速度与汽车速度之间存在着差异,因而会导致车轮与路面之间产生滑移,当车轮以纯滚动方式与路面接触时,其滑移率为零；当车轮抱死时其滑移率为100％.当滑移率在8％～35％之间时,能传递最大的制动力.制动防抱死的基本原理就是依据上述的研究成果,通过控制调节制动力,使制动过程中车轮滑移率控制在合适的范围内,以取得最佳的制动效果.ABS系统硬件构成主要由传感器(包括轮速传感器、减速度传感器和车速传感器)、电子控制装置、制动压力调节器三大部分组成,形成一个以滑移率为目标的自动控制系统.传感器测量车轮转速并将这一数据传送至电子控制装置上,控制装置是一个微处理器,它根据车轮转速传感器信号来计算车速.在制动过程中,车轮转速可与控制装置中预先编制的理想减速度的特性曲线相比较.如果控制装置判断出车轮减速度太快和车轮即将抱死时,它就发出信号给液压调节器,液压调节器可根据来自控制装置的信号对制动器的卡钳或轮泵的油压进行控制(作用、保持、释放、重新作用).这一动作,每秒钟能出现10次以上.

Anti-lock braking system in the car before the vehicle is used in open-loop braking system. Its characteristics are the size of brake torque control force only with the driver, and the braking force distribution from the brake on the size and type. In the absence of state feedback wheel movement, can not detect the speed of the wheels during braking and locking case, the car can not be adjusted pursuant to the wheel cylinder or brake pressure chamber size. Therefore, in emergency braking, the wheels inevitably drag on the ground sliding locking phenomenon. When the wheel lock, the ground of the lateral attachment of poor performance, can provide lateral adhesion is very small, small car by any external force direction will appear under the effect of instability problems, prone to traffic accidents. In the wet pavement or snow and ice braking, the phenomenon of instability of this direction will be more serious. Automobile anti-lock braking system (Anti-lock Braking System referred to as ABS) the emergence of a fundamental solution to the car's wheel lock during braking problems. Its basic function is perceived by the sensor instantaneous state of motion of each wheel, and according to its state of motion accordingly adjust the size of brake torque to avoid locking the wheels and, therefore, is a closed-loop braking system.
It is the electronic control technology in the automotive application of the most accomplished one of the items, automotive anti-lock braking system allows the car to maintain directional stability when braking and shorten stopping distances, improve traffic safety.
One, ABS works
Vehicle braking wheel speed and vehicle speed because there are differences between, and thus lead to slip between the wheels and the road surface, when the wheels of pure rolling contact with the road surface, the slip rate is zero; when the wheel lock When the slip rate of 100%. When the slip rate of 8% to 35%, can pass the maximum braking force. ABS is based on the basic principles of research results, by controlling the braking force adjustment, so that during braking the appropriate wheel slip rate control range in order to get the best braking effect. ABS system hardware constituted mainly by the sensors (including the wheel speed sensor, speed sensor and speed sensor less), electronic control unit, brake pressure regulator has three major components, forming a target slip rate of the automatic control system. Wheel speed sensor and the data sent to the electronic control device, the control device is a microprocessor, it is based on wheel speed sensor signal to calculate speed. During braking, wheel speed and control devices can be prepared in advance by the speed of the ideal characteristic curve compared. Determine if the control wheel and the wheel is about to cut too fast locking time, it send a signal to the hydraulic pressure regulator, hydraulic modulator according to the signal from the control unit of brake caliper or wheel of the hydraulic pump control ( role in maintaining, releasing, re-role.) This action can occur more than 10 times per second.