Chapter 10 Braking system制动系统.ppt

Braking System１１. Overview of braking system２２. Brakes３３. Non-power brakes４４. Power-assisted brakes５５. Power brakes６６. Additional retarder brake system ７７. ABS (Antilock Braking system)Energy is required when a vehicle is accelerated from rest to a certain speed. A proportion of that energy is now stored in the vehicle and is called kinetic energy. In order to reduce the speed of the vehicle, the brakes have to convert the kinetic energy to heat energy; the speed of conversion governs the rate at which the vehicle slows down.汽车从汽车从原地起步加速原地起步加速到某一速度需要能量。

储存在汽车中到某一速度需要能量储存在汽车中的那部分能量称为的那部分能量称为动能动能要降低车速要降低车速, ,制动器必须把汽车的制动器必须把汽车的动能转换为动能转换为热能热能；转；转换换的速度的速度决定决定了汽车了汽车减速减速的快慢Qu.1: What’s the main function of braking system?Main parts of braking system1. The energy-supplying device 供能装置供能装置2. The control device 控制装置控制装置3. The transmission device 传动装置传动装置4. The brake 制动器制动器Main parts of braking systemDisc BrakeBrake caliperBrake hose/lineBrake pedalMaster cylinderWheel cylinderDrum BrakeMetering Valve 节压阀节压阀Proportioning Valve 比例阀比例阀 Check Valve 单向阀单向阀Solenoid Valve 电磁阀电磁阀Combination Valve 组合阀组合阀Delay Valve 延迟阀延迟阀Modulator Valve 调节阀调节阀Qu.2: How to differentiate the types of braking system?• Service braking system 行车制动系行车制动系• Parking braking system 驻车制动系驻车制动系• Additional retarding braking system 缓速制动系缓速制动系• muscular energy braking system (non-power braking system)• energy assisted braking system (power assisted braking system)• non-muscular energy braking system (power braking system)• inertial braking system• gravity braking systemAccording to the types of energy used:目前使用的制动系统有三种类型：目前使用的制动系统有三种类型：行车制动系，住车制行车制动系，住车制动系和辅助制动系动系和辅助制动系．行车制动系和住车制动系有．行车制动系和住车制动系有独立的独立的控制和传动装置．行车制动系通常使用脚刹，而驻车制控制和传动装置．行车制动系通常使用脚刹，而驻车制动系通常使用手刹．动系通常使用手刹．The three types of braking systems are in use today: service braking system, parking braking system and additional retarding-braking system. The service braking system and the parking braking system have separate control and transmission devices. The service braking system is normally foot-operated, while the parking braking system is hand-operated.According to transmission device • Single-circuit braking system• Multi-circuit braking systemMechanical braking system 机械制动机械制动Hydraulic braking system 液压制动液压制动Pneumatic braking system 气压制动气压制动Electromagnetic braking system 电磁制动电磁制动Combination braking system目前使用的制动器有两种类型：目前使用的制动器有两种类型：鼓式制动器鼓式制动器和和盘式制动器盘式制动器．从．从19761976年开始，所有的汽车前轮都使用盘式制动器年开始，所有的汽车前轮都使用盘式制动器, , 大部分汽车大部分汽车后轮使用的是鼓式制动器后轮使用的是鼓式制动器. . 在盘式制动器和鼓式制动器中都使在盘式制动器和鼓式制动器中都使用液压系统用液压系统. . 液压系统把制动踏板与每个车轮的制动部件相连液压系统把制动踏板与每个车轮的制动部件相连接接. .Types of the brakeTwo types of brakes are used in modern cars: drum brakes and disc brakes. Since 1976, all cars have used disc brakes on the front wheels. Most cars use drum brakes on the rear wheels . In both drum and disc brakes, a hydraulic system applies the brakes. The hydraulic system connects the brake pedal to the brake parts at each wheel.• Drum brake 鼓式制动器鼓式制动器• Disc brake 盘式制动器盘式制动器• Wheel cylinder brake• Cam actuated brake• Wedge actuated brake•Disc brake with fixed caliper•Disc brake with floating caliperOperation process of drum brakePistonWheel cylinderBrake DrumFriction PadAnchor pinBrake shoeReturn springMaster cylinderThese have two shoes, anchored to a stationary back-plate, which are internally expanded to contact the drum by hydraulic cylinders or a mechanical linkage. 这种制动器有两个这种制动器有两个固定固定在在制动底板制动底板上的上的制动制动蹄蹄，通过，通过液压轮缸液压轮缸或或机械杆系机械杆系作用从内侧向作用从内侧向外推开与制动鼓接触。

外推开与制动鼓接触Main types of Drum brakesSimplex drum brake (Leading trailing shoe brake) 领从蹄式制动器领从蹄式制动器Duo-trailing shoe brake (Two trailing shoe brake) 双从双从蹄式制动器蹄式制动器Double leading shoe brake 单向双领蹄单向双领蹄Duo-duplex drum brake（（Dou two leading shoe brake）　）　双向双领蹄式制动器双向双领蹄式制动器Uni-servo drum brake 单向自增力式制动器单向自增力式制动器Duo-servo drum brake 双向自增力式制动器双向自增力式制动器 Simplex drum brake 领从蹄式制动器领从蹄式制动器Trailing shoeLeading shoeIn the case of the simplex brake, C*(brake factor) is the sum of the values for the individual shoes, and is ≈2.0（（referred to a specific coefficient of friction) A disadvantage of this design is the great difference in the braking effect between the two brake shoes, and the resulting greatly increased wear on the leading shoe. For this reason, the trailing shoe is often equipped with a much thinner lining than the leading shoe.就就领从蹄领从蹄而言而言，， C*(制动因数制动因数)表示各蹄的值的总数，且表示各蹄的值的总数，且≈２２.００(特指某一摩擦系数）．这种设计的特指某一摩擦系数）．这种设计的缺点缺点是两个制动蹄制是两个制动蹄制动效果有很大不同，动效果有很大不同，结果结果大大增加了领蹄上的摩擦．因此，大大增加了领蹄上的摩擦．因此，从蹄的从蹄的摩擦衬片摩擦衬片比领蹄薄．比领蹄薄．Simplex drum brake 领从蹄式制动器领从蹄式制动器Dou-duplex drum brakeAn advantage of this type of brake is the nearly equal brake lining wear on both shoes and the higher internal transmission ratio in comparison to simplex brakes.这种制动器的优点是两个蹄上这种制动器的优点是两个蹄上制动衬片制动衬片磨损几磨损几乎相同，与乎相同，与领从蹄制动器领从蹄制动器相比它的内传动比较相比它的内传动比较高．高．Dou-duplex drum brake 双向双领蹄式制动器双向双领蹄式制动器Many cars have 2 L.S. front brakes and L.&T. rear brakes. The more powerful front brakes take advantage of the transference of weight from the rear to the front which occurs when the brakes are applied. 多数汽车前轮采用多数汽车前轮采用双领蹄式制动器双领蹄式制动器，后轮采用，后轮采用领从蹄式制动器领从蹄式制动器。

前轮制动器制动力很大，充前轮制动器制动力很大，充分分利用利用制动时制动时轴荷轴荷由后轮向前轮由后轮向前轮转移转移的特点Duo-servo drum brakeCam actuated brakeThis type of drum brake has an application mechanism which is simpler, more reliable and insensitive to temperature. It comprises diaphragm cylinder, automatic slack adjuster, brake shaft and S-cam.这类凸轮制动器有一套简单，稳定，这类凸轮制动器有一套简单，稳定，恒温恒温机构．它机构．它包括包括膜片弹簧制动器室膜片弹簧制动器室，，自动调整器自动调整器，制动轴和，制动轴和S S凸凸轮轮. .Cam actuated brakeThe main disadvantage of drum brakes is that the friction area is almost entirely covered by a lining, so most heat must be conducted through the drum to reach the outside air to cool. 鼓式制动器的主要缺点是它的摩擦面几乎鼓式制动器的主要缺点是它的摩擦面几乎完全被完全被摩擦衬片摩擦衬片覆盖了，制动过程中大多覆盖了，制动过程中大多数的热要通过制动鼓数的热要通过制动鼓传传给大气进行冷却。

给大气进行冷却Disc brake 盘式制动器盘式制动器•Disc brake with fixed caliper•Disc brake with floating caliper制动钳体制动钳体calipercaliper活活 塞塞pistonpiston制动块制动块Friction padFriction pad制动盘制动盘discdiscDisc brake with fixed caliperDisc brake with floating caliperExposed to the air, disc brakes radiate the heat to the air better than drum brakes: This means that the brake can be operated continuously for a longer period, i.e. they have a greater resistance to fade (fall-off in brake efficiency due to heat).由于暴露于空气中，盘式制动器的散热效果由于暴露于空气中，盘式制动器的散热效果比鼓式的要好：这意味着盘式制动器能比鼓式的要好：这意味着盘式制动器能持续持续使用使用更长的时间，也就是说其更长的时间，也就是说其抗热衰退性抗热衰退性（因受热导致制动效能下降）要好得多。

因受热导致制动效能下降）要好得多常用在许多常用在许多乘用车乘用车上的盘式制动器正逐渐被用于上的盘式制动器正逐渐被用于商用车商用车. . 它们它们除除用于用于快速客车快速客车外外, , 目前盘式制动器在商用车上的目前盘式制动器在商用车上的用途基本限制在前轴制动用途基本限制在前轴制动, , 因为因为商用车重量商用车重量约等于约等于7.57.5吨吨时，在某种意义上，其驱动时，在某种意义上，其驱动方式方式与乘用车相似与乘用车相似Disc brakes as used in most passenger cars are slowly beginning to be used in commercial vehicles as well. Aside from their use in fast coaches, current use of disc brakes in commercial vehicles is primarily limited to front-axle brakes for commercial vehicles up to a weight of approx. 7.5 t which are driven in a manner similar to passenger cars. Disadvantage ：：• Short brake pad life when used on heavy-duty commercial vehicles;• Higher acquisition and operating costs .Advantage of disc brakes:• Better gradual braking efficiency;• Equal wear of the inboard and outboard brake pads ;• Brake noise is better suppressed ;• Relatively constant brake factor performance with lower susceptibility to fading .The master cylinder contains two separate sections, there is a piston in each section and both pistons are connected to a brake pedal in the driver's compartment. 制动主缸制动主缸由两个分开的由两个分开的管路管路组成，每个管路都组成，每个管路都有一个活塞，两个活塞都与有一个活塞，两个活塞都与驾驶室驾驶室里的制动踏里的制动踏板相连接。

板相连接Non-power brakesMain parts of braking systemDisc BrakeBrake caliperBrake hose/lineBrake pedalMaster cylinderWheel cylinderDrum Brake当驾驶员踩下制动踏板时，主缸两套管路中的两活塞移动．当驾驶员踩下制动踏板时，主缸两套管路中的两活塞移动．迫使迫使制动液流出制动液流出经过制动管路进入各车轮的制动装置中．经过制动管路进入各车轮的制动装置中．在典型制动系统中，制动液流从主缸的一条管路流向两个前轮制在典型制动系统中，制动液流从主缸的一条管路流向两个前轮制动装置中，另一条管路的制动液流向两个后轮制动装置．其目的动装置中，另一条管路的制动液流向两个后轮制动装置．其目的是，如果其中一套管路是，如果其中一套管路失灵失灵，另一条管路仍然能够提供制动．，另一条管路仍然能够提供制动．When the brake pedal is pushed by the driver, the two pistons move in the two sections of the master cylinder. This forces brake fluid out and through the brake lines, or tubes, to the brake mechanisms at the wheels. In a typical system, the brake fluid from one section of the master cylinder goes to the two front-wheel brakes. The brake fluid from the other section goes to the two rear-wheel brakes. The purpose of this is that, if one section fails, the other section will still provide braking.制动踏板制动踏板Brake pedal真空助力器真空助力器Vacuum booster储液室储液室Brake-fluid reservoir盘式制动器盘式制动器Disk brake串列制动主缸串列制动主缸Tandem master cylinder比例阀比例阀Proportioning valve真空管真空管Vacuum connection鼓式制动器鼓式制动器Drum brake Power-assisted brakesThe operating principle of the power-assisted system is the same as for a non-power system. However, braking force is increased through the use of a vacuum booster unit. Atmospheric pressure helps to push the brake pedal. Thus, less muscle effort is required. （（P.108））伺服制动系伺服制动系的工作原理与的工作原理与人力制动系人力制动系相同。

然而，伺服制相同然而，伺服制动系通过采用动系通过采用真空助力装置真空助力装置来增加制动力来增加制动力大气压力大气压力有助有助于踩下制动踏板这样，制动时几乎不需要于踩下制动踏板这样，制动时几乎不需要人力人力(Spark-ignition)(Spark-ignition)点燃式发动机中，点燃式发动机中，通过通过连连接发动机的接发动机的进气支管进气支管产生真空产生真空，而柴油发动，而柴油发动机使用机使用真空泵真空泵．．In SI engines, vacuum is generated via a connection to the engine intake manifold, and diesel engines use a vacuum pump.The vacuum booster is a pedal-force booster which is combined with a tandem master cylinder. The boost factor i can be varied in design by an appropriate choice of lever control. 真空助力器真空助力器是一个与是一个与串列制动主缸串列制动主缸连在一起的踏板助力器．设计连在一起的踏板助力器．设计时时助力因数助力因数i i可选择可选择适当适当的杠杆控制而不同．的杠杆控制而不同．通过杠杆控制，一定通过杠杆控制，一定比例比例的助力的助力叠加叠加在踏板力上并同时对串列式在踏板力上并同时对串列式制动主缸作用．同时，反作用力传给驾驶员，使他能正确的制动主缸作用．同时，反作用力传给驾驶员，使他能正确的估计估计制动行为．制动行为． Via the lever control, a proportional assisting force is superimposed on the pedal force, and both act together on the tandem master cylinder. At the same time, a reactive force is conveyed to the driver, which enables him to meter the braking action correctly.Tandem master cylinder（串列式制动主缸）（串列式制动主缸）双储液室双储液室Two-chamber fluid reservoir补偿孔补偿孔Snifter holeRear brake circuit IFront brake circuit II中间活塞中间活塞Intermediate piston机架机架Housing推杆推杆Push-rodCompression spring工作原理工作原理( (串列式制动主缸串列式制动主缸）：推杆活塞经过）：推杆活塞经过补偿孔补偿孔ⅠⅠ迫使迫使制制动液流入制动回路动液流入制动回路ⅠⅠ．．弹簧压缩及制动回路弹簧压缩及制动回路ⅠⅠ上产生的压力上产生的压力促动促动中间活塞中间活塞，使它经，使它经过补偿孔过补偿孔ⅡⅡ并在制动回路并在制动回路ⅡⅡ上上产生产生压力．压力．Operation principle (Tandem master cylinder): after passing over snifter holeⅠ, the push-rod piston forces the brake fluid into brake circuit Ⅰ. The compression of the spring and the pressure buildup in brake circuit I actuates the intermediate piston, which passes over snifter hole Ⅱ and builds up pressure in brake circuit Ⅱ. Tandem master cylinder （串列式制动主缸）（串列式制动主缸）制动回路制动回路I I上的孔为后轮鼓式制动器提供制动液，上的孔为后轮鼓式制动器提供制动液，其内有一个其内有一个预压阀预压阀，它保证制动踏板释放时有约，它保证制动踏板释放时有约150kPa150kPa残余压力残余压力, ,阻止空气通过轮缸密封处进入阻止空气通过轮缸密封处进入．The port for brake circuit I, which supplies the rear drum brakes, has a pre-pressure valve which assures a residual pressure of approx. 150kPa when the brakes are released. This prevents the entry of air through the wheel-cylinder seals.Matched to the respective vehicle data, there are various kinds of brake-pressure-regulating valve: 1) with fixed changeover pressure; 2) load-sensitive with variable changeover pressure.Brake pressure regulating valve制动调压阀制动调压阀 当前轴总在后轴之前抱死时可获得制动稳定性，它当前轴总在后轴之前抱死时可获得制动稳定性，它与汽车载重无关与汽车载重无关．通过安装在连接后轮的制动管路上的．通过安装在连接后轮的制动管路上的制动调压阀制动调压阀可可以得到正确的制动力分配．以得到正确的制动力分配．The more heavily the driver brakes, the greater is the dynamic shifting of weight from the rear axle to the front axle. With the vehicle empty, the braking force at the rear axle may be so great that the rear axle locks before the front axle. This can lead to instability when braking, i.e. to skidding . Braking stability is obtained when, irrespective of vehicle loading, the front axle always locks before the rear axle. The correct braking-force distribution can be achieved by brake–pressure-regulating valves which are installed in the brake lines to the wheels of the rear axle.驾驶员制动力越大，从后轴到前轴动态转移的重量越大．汽车空载时，驾驶员制动力越大，从后轴到前轴动态转移的重量越大．汽车空载时，后轴上制动力很大以至后轴在前轴之前后轴上制动力很大以至后轴在前轴之前抱死抱死．这导致制动．这导致制动不稳定不稳定，即，即发生滑动．发生滑动．开始开始制动时，控制弹簧使坐在制动时，控制弹簧使坐在阶阶梯形活塞梯形活塞上的阀打开，直上的阀打开，直到制动压力按照阶梯形活塞有效面积，达到与控制弹簧力到制动压力按照阶梯形活塞有效面积，达到与控制弹簧力相同相同的程度．的程度．During initial braking, the control spring keeps the valve seat at the stepped piston open until the brake pressure has reached a level which, according to the active area of the stepped piston, corresponds to the force of the control spring.Inertial braking systemRetarder Braking system缓速制动系统缓速制动系统 Two main categories:1) Exhaust Brakes2) Electrodynamic RetardersThe components of compressed air brakes1、、Energy-supplying device 供能装置供能装置 2、、Control device 控制装置控制装置 3、、Executive device 　　 执行装置执行装置 1 Compressor 空气压缩机空气压缩机 2 brake cylinder 制动气室制动气室3 brake valve 制动阀制动阀 4 water-drain valve 放水阀放水阀5 air reservoir 湿湿储气罐储气罐 6 master reservoir 主主储气罐储气罐 7 pressure regulator 调压阀　　　调压阀　　　 8 barometer 气压计气压计9 bugle 喇叭喇叭压缩机压缩机用做能源一般是用做能源一般是活塞型活塞型的．通过的．通过自动进、排自动进、排气阀气阀进入的空气在其内被压缩．进入的空气在其内被压缩．A compressor is used as the energy source, and is usually of the plunger type; the intake air is compressed via automatic suction and delivery valves.Service brake valve行车制动阀行车制动阀组合式组合式制动室制动室由由行车制动器行车制动器的的单室膜片弹簧制动气室单室膜片弹簧制动气室和和驻驻车制动器车制动器弹簧助力装置弹簧助力装置组成．制动气室和弹簧助力装置串组成．制动气室和弹簧助力装置串联在一起并对联在一起并对压力杆压力杆作用．作用．The combination brake cylinder consists of a single-chamber diaphragm cylinder for the service brakes and a spring-brake actuator for the parking brakes. The cylinder and spring brake actuator are in tandem and act on a common pressure rod.Electrohydraulic braking systems are designed to allow electonic control of vehicle braking while retaining a reduced hydraulic system. The EHB control unit receives inputs from sensors connected to the brake pedal. 电液制动系统电液制动系统允许电子控制汽车制动允许电子控制汽车制动, ,同时同时保留保留了了简化简化的液压系的液压系统统. .电液制动系统控制单元接受与制动踏板连接的传感器的输入电液制动系统控制单元接受与制动踏板连接的传感器的输入. .正常正常工作时工作时, , 后备阀后备阀关闭关闭, , 控制器通过由液压泵驱动的电动机控制器通过由液压泵驱动的电动机控制控制制动器制动器. . 当控制器进入当控制器进入失效安全模式失效安全模式时时, ,后备阀打开后备阀打开, , 并允并允许传统的液压回路控制制动器许传统的液压回路控制制动器. . In normal operation, a backup valve is closed and the controller activates the brakes of the wheel through an electric motor driven hydraulic pump. When the controller goes into a fail-safe mode, the backup valve is opened, which allows the brakes to be controlled through a conventional hydraulic circuit.（P.122） Additional retarder brake system辅助缓速制动系统辅助缓速制动系统a. Exhaust retarder 　　　　　　　　 排气缓速器排气缓速器b. Hydrodynamic retarder 　　 液力缓速器液力缓速器c. Electromagnetic retarder 电磁缓速器电磁缓速器d. Traction motor retarder 牵引电机缓速器牵引电机缓速器e. Aerodynamic retarder　　　　 空气动力缓速器空气动力缓速器为了刹车，用电池或发电机给为了刹车，用电池或发电机给励磁线圈励磁线圈供电从而产生供电从而产生磁磁场场．当转子经过磁场时感应生成．当转子经过磁场时感应生成感应电涡流感应电涡流．这样产生．这样产生的的制动力矩制动力矩的的大小大小是定子线圈中是定子线圈中励磁电流励磁电流的函数．的函数．In order to brake the vehicle, the field coils are supplied with current (from the battery or alternator) and generate a magnetic field. Eddy currents are induced in the rotors as they pass through this field. This generates a braking torque whose magnitude is a function of the excitation of the stator coils.Brake slip 滑动率滑动率 （（P.112P.112））λ＝＝ [(νF－－ νR)/ νF] ×100%　　　　　　　　 λ＝０；　　＝０；　　 λ＝＝100％．％．μB－－Braking-force coefficient 制制动力系数力系数μS－－Lateral-force coefficient　　 侧向力系数侧向力系数μBμsλ轮缸轮缸 电控电控 单单元元电电动动机机液压泵液压泵主缸主缸线线圈圈电磁电磁阀阀轮速传感器轮速传感器Wheel cylinderWheel-speed sensorElectronic controllersolenoid-valvecoilmotorhydraulic pumpplunger Main parts of ABSThe function of an anti-lock, or anti-skid, braking system is to prevent the wheels from locking under hard braking. Maximum braking force is obtained just before the wheels lock and skid. Such anti-skid systems are useful on slippery surfaces, such as ice and snow, where the wheels may lock easily. 防抱死制动系统的作用是防止在防抱死制动系统的作用是防止在强制动强制动条件下车轮条件下车轮抱死。

只在车轮抱死拖滑时才会获得最大制动力只在车轮抱死拖滑时才会获得最大制动力这类防滑系统在冰、雪等这类防滑系统在冰、雪等光滑路面光滑路面非常实用，因为非常实用，因为在这些路面上车轮容易抱死在这些路面上车轮容易抱死 The wheel-speed sensor monitors the motion of the wheel. If one wheel shows signs of locking, there is a sharp rise in peripheral wheel deceleration and in wheel slip. If these exceed defined critical values, the controller sends commands to the solenoid-valve unit to stop or reduce the buildup of wheel-brake pressure until the danger of lock-up has passed. 轮速传感器轮速传感器监控着车轮的运动，如果一个车轮出现抱死信号，监控着车轮的运动，如果一个车轮出现抱死信号，也就是也就是外车轮外车轮减速度急剧增大且车轮开始滑动．如果超出定减速度急剧增大且车轮开始滑动．如果超出定义的义的临界值临界值，，控制器控制器给给电磁阀电磁阀发送命令来停止或降低制动压发送命令来停止或降低制动压力，直到抱死的危险消除．然后制动力再增大确保车轮制动力，直到抱死的危险消除．然后制动力再增大确保车轮制动力不会力不会不足不足．． The brake pressure must then be built up again in order to ensure that the wheel is not under-braked.轮速传感器由运动的轮速传感器由运动的齿圈齿圈和和磁感应传感头磁感应传感头构成．齿圈构成．齿圈安装在安装在轮毂轮毂上，车轮转动时，在上，车轮转动时，在传感头传感头上产生频率与上产生频率与轮速成正比的轮速成正比的交流电压交流电压．．A wheel-speed sensor consists of a toothed pulse ring and an inductive wheel-speed pickup. The pulse ring is mounted on the hub and , as the wheel rotates, produces in the wheel-speed pickup an A.C. voltage, the frequency of which is proportional to the wheel speed. A.C. Alternating Current 交流电交流电通过来自通过来自传感头传感头的信号，的信号，微机微机不仅计算出车速，还计算出减速不仅计算出车速，还计算出减速度和加速度．参考度和加速度．参考车速车速由由两对角线位置车轮两对角线位置车轮的轮速构成．用这的轮速构成．用这个参考速度和个参考速度和单个单个轮速可以计算出每个车轮的轮速可以计算出每个车轮的滑动率滑动率．车轮是．车轮是否有抱死否有抱死趋势趋势决定于车轮的加速度和滑动信号．决定于车轮的加速度和滑动信号．From the signals from the wheel-speed pickups, these microcomputers calculate the wheel speeds as well as the wheel decelerations and accelerations. A vehicle reference speed is formed from the wheel speeds of two diagonally opposite wheels. With this reference speed and the individual wheel speeds it is possible to calculate the brake slip for each wheel.　　If a wheel has a tendency to lock, this is determined from the wheel-acceleration and slip signals. (P.120)ABSABS系统的工作原理系统的工作原理①①常规制动（升压）过程常规制动（升压）过程轮轮柱柱塞塞电控电控单单元元电电动动机机液压泵液压泵主缸主缸线线圈圈电磁阀电磁阀轮速传感器轮速传感器②②轮缸减压过程轮缸减压过程③③轮缸保压过程轮缸保压过程④④轮缸增压过程轮缸增压过程。