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1、 Unit 14 ABS and TCS第十四课 防抱死制动系统和牵引力控制系统14.1 制动系统基本原理和基本制动There are two usual force inputs to a motor vehicle: engine torque to provide acceleration (+ X acceleration) and brake friction to provide deceleration(-X acceleration).对于汽车，通常有两个输入力：发动机转矩提供加速力（X 正方向加速）和制动摩擦提供减速力（ X 负方向加速） 。幻灯片 5When an oper
2、ator actuates the brake pedal, he or she is actually pushing on a lever that pushes a piston in a master cylinder to generate hydraulic pressure that is transmitted through the brake lines to the wheel actuators (either wheel cylinders or caliper pistons). 当驾驶员动作制动踏板，他（她）实际上推动拉杆，由拉杆推动主缸的活塞来产生液压。液压通过
3、制动管路传送到车轮的作动器上（轮缸或者制动钳活塞） 。幻灯片 6The wheel actuators force a friction material (brake shoes or disk pads) against a rotating surface (brake drums or disk rotors)to generate a force that stops the vehicle.车轮作动器强迫摩擦材料（制动蹄块或制动衬片）与旋转的表面接触（制动鼓或制动盘） ，从而产生使车辆停止的力。幻灯片 7The energy to stop the vehicle is norma
4、lly dissipated as heat in the drums or rotors. Thus, applying the brakes is really the act of dissipating the rolling energy of the vehicle as heat, hence slowing the vehicle down.停止车辆的能量通常被转化为热能形式在制动鼓或制动盘消耗掉。因此，施加制动实际上就是将汽车的动能转为热能并消耗掉，从而使汽车减速。幻灯片 8The operation of the braking system depends on the
5、integrity of the hydraulic system. Modern boosted master cylinders can generate 2000 psi or more, and the hydraulic system must distribute that pressure without leaking.制动系统的操作取决于整个液压系统。现代助力型主缸可以产生 2000psi，甚至更多的压强，液压系统必须要能够将压力分配，并不产生泄漏。幻灯片 9Almost all modern braking systems use a booster (or operato
6、r force amplifier) that uses engine vacuum to increase the force the brake lever applies to the master cylinder.几乎所有的现代制动系统都使用助力器（或操作力放大器） 。它利用发动机真空增加制动拉杆施加在主缸上的力。幻灯片 10Generally, disk brakes require higher application pressure than do drums because they are not self-actuating.一般来说，盘式制动器比鼓式制动器需要施加更多
7、的制动力，因为它不能够自行增力。幻灯片 11When drum brakes are combined with disk brakes in a vehicle (usually with drums in the rear), there is always “a proportioning valve” to proportionally reduce the effective hydraulic pressure at the drum brake wheel cylinders and to always keep the rear wheels turning to preser
8、ve directional stability.当鼓式制动器和盘式制动器在汽车上混合使用（一般鼓式制动器用于后轮）的时候，通常需要一个比例阀按比例减少施加在鼓式制动器轮缸的液压，从而总是使得后轮旋转，保证方向稳定性。幻灯片 1214.2 Antilock Braking Systems14.2 防抱死制动系统A vehicle braking system, including the tires is most effective, i.e., produces the optimum retarding force, when the wheel speeds are approxima
9、tely, 85% to 90% of the vehicle speed. The difference (100%-85%=15%) is called the percent slip of a particular wheel.当车轮速度大约为 85%至 90%的车速时，汽车轮胎制动系统最有效，也就是说它可以产生最优的制动力。这个 15%的差值被称作车轮的滑移率。幻灯片 13The 10% to 15% slip retarding force is greater than the locked wheel retarding force, so optimum braking is
10、 achieved when the slip is 10% to 15% and no more.当滑移率在 10%至 15%之间时，制动力要大于车轮抱死时的制动力，因此只有当滑移率在 10%至 15%之间，系统取得最佳制动效果。幻灯片 14Over-applying foundation brakes can cause wheels to lock (100% slip), so a system that prevents this can improve braking effectiveness. Antilock braking systems (ABS) have been d
11、eveloped to do this. 过多制动会导致车轮抱死（100%的滑移率） 。因此，能够防止这种现象发生的系统就可以提高制动效果。防抱死制动系统(ABS)的设计就是实现这个目的。幻灯片 15However, prevention of lock to improve braking effectiveness is not the most important reason for ABS. Once a wheel is locked, it does not provide any lateral control of the vehicle(+/-Y axis) , and i
12、f multiple wheels lock, the vehicle will start to yaw.但是，通过防止车轮抱死来提高制动效果并不是 ABS 的首要目的。一旦车轮抱死，它无法给汽车提供任何横向控制（正负 Y 方向） ，如果多个车轮抱死，汽车开始偏移。幻灯片 16This means that if the rear wheels lock, the vehicle will tend to spin out (rear end moving forward) , and if the front wheels lock, the vehicle cannot be steer
13、ed. Control of vehicle track is the most important reason for the use of ABS.这意味着如果后轮抱死，汽车趋向侧滑（汽车后端向前运动） 。如果前轮抱死，汽车失去转向能力。因此，控制汽车行驶是 ABS 的首要目的。幻灯片 17It has been shown that for poor road conditions (sand, ice, snow, water, etc.）, a system that prevented wheel lockup and gave significantly increased d
14、irectional control, in exchange for a small loss of absolute stopping distance, provided a major benefit to overall vehicle performance.已经证明，当汽车在较差路面（沙、冰、雪、水等）行驶时，ABS 系统可以防止车轮抱死，显著改善行驶方向控制。这是牺牲较小的制动距离换来的，但对整个汽车性能有大的改善。幻灯片 18 This is accomplished by using an ECU to sense individual wheel speeds, and
15、then isolate and reduce brake fluid pressure to the wheel or wheels that are locking up. The controller is an ECU, the controlled parameter, is wheel cylinder pressure (via electrical solenoid valves), and the feedback elements are individual electronic wheel speed sensors (WSS).这是通过使用 ECU 来检测单个车轮转速
16、，并对锁死的车轮进行保压和减压控制实现的。ABS 系统的控制器是 ECU，受控参数是轮缸压力（通过电磁阀调节） ，反馈元件是单个车轮电子转速传感器。幻灯片 19The WSS signals are typically generated via a pickup coil mounted adjacent to a toothed ring at each controlled wheel, where the pickup coil generates a varying voltage output proportional to the amplitude and frequency of the magnetic flux change as the ring teeth pass by it.轮速传感器信号是由一个靠近每个被控轮齿圈安装的耦合线圈产生的。当齿圈经过耦合线圈，耦合线圈产生一个与磁通量幅值和频率变化成比例变化的电压输出信号。幻灯片 20By monitoring the
