Tài liệu đào tạo ABS TCS ESP book Hyundai

Tài liệu đào tạo ABS TCS ESP book Hyundai Tài liệu đào tạo ABS TCS ESP book HyundaiTài liệu đào tạo ABS TCS ESP book HyundaiTài liệu đào tạo ABS TCS ESP book HyundaiTài liệu đào tạo ABS TCS ESP book HyundaiTài liệu đào tạo ABS TCS ESP book HyundaiTài liệu đào tạo ABS TCS ESP book HyundaiTài liệu đào tạo ABS TCS ESP book HyundaiTài liệu đào tạo ABS TCS ESP book HyundaiTài liệu đào tạo ABS TCS ESP book HyundaiTài liệu đào tạo ABS TCS ESP book HyundaiTài liệu đào tạo ABS TCS ESP book HyundaiTài liệu đào tạo ABS TCS ESP book HyundaiTài liệu đào tạo ABS TCS ESP book HyundaiTài liệu đào tạo ABS TCS ESP book Hyundai

ABS/TCS/ESP TRAINING GUIDE

1 HYDRAULIC FUNDAMENTALS

-1.1 PASCAL’S LAW

-1.2 FORCE

-1.3 PRESSURE

-1.4 PRESSURE ON A CONFINED FLUID

-1.5 FORCE MULTIPLICATION

-1.6 PISTON

TRAVEL -1.7 HYDRAULIC SYSTEM

-1.8 THE FLUID RESERVOIR

-1.9 THE PUMP

-1.10 VALVE MECHANISM

-1.11 AN ACTUATING MECHANISM

-2 ABS GENERAL

-2.1 A BRIEF HISTORY OF ABS

-2.2 ADVANTAGES OF ABS

-2.3 ABS TYPES

-2.4 ABSCM

-2.5 TYPICAL ABS CONTROL CYCLES

-2.6 PHYSICAL PRINCIPLES

-2.7 SELECT LOW CONTROL FOR THE REAR WHEEL

-2.8 ABS GENERAL CONSTRUCTION

-2.9 WHEEL SPEED SENSOR

-2.11 G SENSOR

-2.12 SYSTEM LINE-UP

-3 LUCAS (F2, WITHOUT EBD)

-3.1 LUCAS ABS CONTENTS

-3.2 LUCAS ABS HCU & ABSCM

-3.3 LUCAS ABS CONSTITUTION

-3.4 SPECIFICATIONS

-3.5 LOCATION

-3.6 COMPONENTS

-3.7 LUCAS ABS OPERATION

-3.8 LUCAS ABS HYDRAULIC CIRCUIT

-3.9 LUCAS ABS OPERATION

-3.10 CONNECTORS

-3.11 SRI LAMP FLASH CODE

-3.12 INPUTS / OUTPUTS

-3.13 LUCAS ABS TROUBLESHOOTING

-3.14 LUCAS ABS WIRING DIAGRAM 1 (KEY OFF)

-3.15 LUCAS ABS WIRING DIAGRAM 2 (KEY ON)

-3.16 LUCAS ABS WIRING DIAGRAM 2

-3.17 LUCAS ABS WIRING DIAGRAM 3 (ABS FAILURE)

-3.18 LUCAS ABS WIRING DIAGRAM 3

-4 INTEGRATED ABS/TCS

-4.1 HYDRAULIC CONTROL UNIT(HCU)

-4.2 HCU OPEATION

4.3 EBD OPERATION

-4.4 ACTIVE WARNING LAMP MODULE

-5 MGH-10 (Mando, with EBD)

-5.1 ABS NEW ACCENT(LC)

-5.2 PRACTICE SHEET

-5.3 ABS (SANTA FE)

5.4 BTCS (SANTA FE)

-6 MGH-20 (Mando, with EBD)

-6.1 ABS (Hyundai coupe: GK)

-6.2 BTCS Matrix(FC)

-6.3 FTCS (Hyundai coupe: GK)

-7 MK-20 (TEVES)

-7.1 ABS (EF SONATA, XG)

7.2 FTCS (EF SONATA, XG)

-8 BOSCH 5.3 (with EBD)

-8.1 ABS 5.3 (NEW EF SONATA)

-8.2 ABD 5.3 (BTCS - NEW EF SONATA)

8.3 ASR 5.3 (FTCS - NEW EF SONATA)

-9 NISSHINBO ABS (with EBD)

-9.1 NT20S2 (TRAJET)

-9.2 NT20Si (TERRACAN)

-9.3 NTY3 (ATOS)

-10 ESP (Electronic Stability Program, TEVES MK25)

-10.1 MK25(CENTENNIAL)

-HYDRAULIC FUNDAMENTALS

From the laboratory data that Pascal collected, he formulated Pascal’s Law, which states :

“Pressure on a confined fluid is transmitted equally in all directions and acts with equal force onequal areas.” This law is a little complex to completely understand as it stands right now Thefollowing illustrations and explanations break down each concept and discuss them thoroughlyenough for easy understanding and retention

1.2 FORCE

A simplified definition of the term force is : the push or pull exerted on an object There are twomajor kinds of forces : friction and gravity The force of gravity is nothing more than the mass, orweight of an object In other words, if a steel block weighing 100 kg is sitting on the floor, then it isexerting a downward force of 100 kg on the floor The force of friction is present when two objectsattempt to move against one another If the same 100 kg block were slid across the floor, there is

a dragging feeling involved This feeling is the force of friction between the block and the floor.When concerned with hydraulic valves, a third force is also involved This force is called springforce Spring force is the force a spring produces when it is compressed or stretched Thecommon unit used to measure this or any force is the kilogram (kg), or a division of the kilogramsuch as the gram (g)

1.3 PRESSURE

Pressure is nothing more than force (kg) divided by area (m2), or force per unit area Given thesame 100kg block used above and an area of 10m2 on the floor ; the pressure exerted by theblock is : 100kg/10m2 or 10kg per square meter

1.4 PRESSURE ON A CONFINED FLUID

Pressure is exerted on a confined fluid by applying a force to some given area in contact with thefluid A good example of this would be if a cylinder is filled with a fluid, and a piston is closely fitted

to the cylinder wall having a force applied to it, thus, pressure will be developed in the fluid Ofcourse, no pressure will be created if the fluid is not confined It will simply “leak” past the piston.There must be a resistance to flow in order to create pressure Piston sealing, therefore, isextremely important in hydraulic operation The force exerted is downward (gravity) ; although, theprinciple remains the same no matter which direction is taken

The pressure created in the fluid is equal to the force applied ; divided by the piston area If theforce is 100 kg, and the piston area is 10m2, then pressure created equals 10kg/m2 =100kg/10m2 Another interpretation of Pascal’s Law is that : “Pressure on a confined fluid istransmitted undiminished in all directions.” Regardless of container shape or size, the pressure will

be maintained throughout, as long as the fluid is confined In other words, the pressure in the fluid

is the same everywhere

The pressure at the top near the piston is exactly same as it is at the bottom of the container, thus,the pressure at the sides of the container is exactly the same as at top and bottom

1.5 FORCE MULTIPLICATION

Going back to the previous figure and using the 10kg/m2 created in the illustration, a force of1,000kg can be moved with another force of only 100kg The secret of force multiplication inhydraulic systems is the total fluid contact area employed The figure shows an area that is tentimes larger than the original area The pressure created with the smaller 100kg input is 10kg/m2.The concept “Pressure is the same everywhere”, means that the pressure underneath the largerpiston is also 10 kg/m2 Reverting back to the formula used before : Pressure = Force/Area or P =F/A, and by means of simple algebra, the output force may be found Example : 10kg/m2 = F(kg) /100m2 This concept is extremely important as it is used in the actual design and operation of allshift valves and limiting valves in the valve body of the transaxle It is nothing more than using adifference of area to create a difference in pressure in order to move an object

1.6 PISTON TRAVEL

Returning to the small and large piston area discussion The relationship with a mechanical lever isthe same, only with a lever it’s a weight-to-distance output rather a pressure-to-area output.Referring to following figure, using the same forces and areas as in the previous example ; it isshown that the smaller piston has to move ten times the distance required to move the largerpiston 1m Therefore, for every meter the larger piston moves, the smaller one moves ten meters.This principle is true in other instances, also A common garage floor jack is a good example Toraise a car weighing 1,000kg, an effort of only 25kg may be required But for every meter the carmoves upward, the jack handle moves many times that distance downward

A hydraulic ram is another good example where total input distance will be greater than the totaloutput distance The forces required in each case are reversed That is, very little effort is required

to produce a greater effort

1.7 HYDRAULIC SYSTEM

Now that some of the basic principles of hydraulics have been covered and understood, it is time toexplore hydraulic systems and see how they work Every pressure type hydraulic system hascertain basic components This discussion will center on what these components are and whattheir function is in the system Later on, the actual systems in the transaxle will be covered indetail The figure reveals a basic hydraulic system that can be used in almost any situationrequiring work to be performed The basic components in this system are : Reservoir, Pump,Valving, Pressure lines, Actuating mechanism or mechanisms

1.8 THE FLUID RESERVOIR

Since almost all fluids are nearly incompressible, the hydraulic system needs fluid to functioncorrectly The reservoir or sump, as it is sometimes called, is a storehouse for the fluid until it isneeded in the system In some systems, (also in the automatic transaxle), where there is aconstant circulation of the fluid, the reservoir also aids in cooling of the fluid by heat transfer to theoutside air by way of the housing or pan that contains the fluid The reservoir is actually a fluidsource for the hydraulic system The reservoir has a vent line, pressure line, and a return line Inorder for the oil pump to operate correctly, the fluid must be pushed up from the reservoir to thepump The purpose of the vent line is to allow atmospheric pressure to enter the reservoir As thepump rotates, an area of low pressure results from the pump down to the reservoir via the pressureline The atmospheric pressure will then push the oil or fluid up to the pump due to a pressuredifference existing in the system

The return line is important because with a system that is constantly operating, the fluid has to bereturned to the reservoir for re-circulation through the system

1.9 THE PUMP

The pump creates flow and applies force to the fluid Remember flow is needed to create pressure

in the system The pump only creates flow If the flow doesn’t meet any resistance, it’s referred to

as free flow, and there is no pressure built up There must be resistance to flow in order to createpressure

Pumps can be the reciprocating piston type (as in a brake master cylinder) or, they can be of therotary type The figure shows three major types of hydraulic oil pumps employing the rotary design

The internal-external type of pump design is used almost exclusively in today’s automatictransaxle.

1.10 VALVE MECHANISM

After the pump has started to pump the oil, the system needs some sort of valving, which will directand regulates the fluid Some valves interconnect passages, directing the fluid where to go andwhen On the other hand, other valves control or regulate pressure and flow The pump will pumpoil to capacity all the time It is up to the valves to regulate the flow and pressure in the system.One important principle to learn about valves in automatic transaxle hydraulics is that the valvescan move in one direction or the other in a passage, opening or closing another passage

The valve may either move left or right, according to which force can overcome the other Whenthe spring force is greater than the hydraulic force, the valve is pushed to the left, closing thepassage

When the hydraulic force builds up enough force to overcome the spring force, the hydraulic forcewill push the valve to the right compressing the spring even more, and re-directing the fluid up intothe passage When there is a loss of pressure due to the re-direction of oil, the spring force willclose the passage again This system is called a balanced valve system A valve that only opensand closes passages or circuits, is called a relay valve

1.11 AN ACTUATING MECHANISM

Once the fluid has passed through the lines, valves, pump, etc., it will end up at the actuatingmechanism This is the point where the hydraulic force will push a piston causing the piston to dosome sort of mechanical work This mechanism is actually the dead end that the oil pump flow willfinally encounter in the system This dead end causes the pressure to build up in the system The pressure works against some surface area (piston) and causes a force to be applied Inhydraulics and transaxle technology, the actuating mechanism is also termed a servo A servo isany device where an energy transformation takes place causing work as a result The clutchassemblies found in the alpha automatic transaxle are actually servos, but they are termed “clutch”for ease of identification

ABS GENERAL

2 ABS GENERAL

2.1 A BRIEF HISTORY OF ABS

▪ 1952 ABS for aircraft by Dunlop

▪ 1969 Rear-wheel-only ABS by Ford & Kelsey Hayes

▪ 1971 Four-wheel ABS by Chrysler & Bendix

▪ 1978 Mass production of Bosch ABS Systems with Mercedes Benz

▪ 1984 Integrated ABS system by ITT-Teves

▪ Since the early 1990s

ABS began to be offered on the mid-size and compact cars due to a significant cost reductionand increased efficiency of the system

2.2 ADVANTAGES OF ABS

Anti-lock Brake Systems are designed to prevent wheel lockup under heavy braking conditions onany type of road condition

The result is that, during heavy braking, the driver :

• retains directional stability(Vehicle Stability)

• stops faster (Shortened Stopping distance, except gravel, fresh snow )

• retains maximum control of vehicle (Steerability)

① If the front wheels lock

▶ it is no longer possible to steer the car

② If the rear wheels lock

▶ the car can become unstable and can start to skid sideways

BRAKING AT CORNERING

<Braking without ABS> <Braking with ABS>

If a car on the different conditions of surface brakes, the wheels on the slippery surface easily lock

up and the vehicle begins to spin But ABS provides vehicle stability until it stops

2.3 ABS TYPES

2.3.1 4-SENSOR 4-CHANNEL TYPE

This type is generally used for FF(Front engine Front driving) car which has X-brake lines Frontwheels are independently controlled and rear wheel control usually follows a select-low logic for

<Braking without ABS> <Braking with ABS>

Low μ road High μ roadSurface

Low μ road

High μ roadSurface

vehicle stability while ABS operation.

2.3.2 4-SENSOR 3-CHANNEL TYPE

This type is generally used for FR(Front engine Rear driving) car which has H-brake lines Frontwheels are independently controlled and rear wheels are controlled together by on brake pipe onthe basis of select-low logic

2.3.3 3-SENSOR 3-CHANNEL TYPE

Front wheels are controlled independently but rear wheels are controlled together by one wheelspeed sensor(ex On the differential ring gear)

2.3.4 1-SENSOR 1-CHANNEL TYPE

Only control the rear wheel pressure by one sensor

2.3.5 SYSTEM EVALUATION

line

Steerability Stability Stopping

Rear : Select Low

4-Sensor 3-Channel H Line Front : Independent control Good Good Fair

Rear : Select Low3-Sensor 3-Channel H Line Front : Independent control Good Good Fair

Rear : Select Low1-Sensor 1-Channel H Line Rear : Select Low No Fair No

1) 4-Sensor 4-Channel type ( Independent control type )

This type has four wheel sensors and 4 hydraulic control channels and controls each wheelindependently Steering safety and stopping distance maintains optimum condition on thehomogeneous road surface

However, on the split-μ road surface, uneven braking force between left wheels

and right wheels generates a Yawing Moment of the vehicle body resulting in vehicle instability.Therefore, most of vehicles with a 4 channel ABS incorporates a select low logic on rear wheels tomaintain the vehicle stability at any road conditions

2) 4-Sensor 3-Channel type (Front wheels: independent control, Rear wheels: Select low control )

In case of FF(Front engine Front driving) car, most vehicle weight concentrated on front wheelsand the center of the mass of vehicle also moves forward while braking allowing almost 70% ofbraking force to be controlled by front wheels

This means that most braking power is generated by front wheels and to get a maximum brakingefficiency while ABS operation, independent control of front wheels is necessarily required

However, rear wheels which performs relatively less braking force are very important to guaranteesvehicle safety while braking That is, while ABS operation of rear wheels on the split road surface,independent control of rear wheel generates uneven braking force resulting in vehicle yawingmoment

To prevent this yawing and to maintain vehicle safety with ABS operation on any kinds of roadsurface, rear wheel braking pressure is managed according to the wheel which shows more lock-

up tendency This control concept is called ‘Select-low control’

3) 4-Sensor 3-Channel type (Front wheels;indendent control,Rear wheels ; Select contnrol )

Vehicle with H-bake line system has this ABS control system 2 channels are for front wheels andthe other one is for rear wheel control Rear wheels are controlled together by a select low controllogic

In case of X-brake line system, 2 channels (2 brake ports in the ABS unit) are required to controlrear wheel pressure because each rear wheel belongs to different brake line

4) 1-Sensor 1-Channel type ( Rear wheels: Select low control )

Vehicle with H-bake line system Only controls rear wheel pressure

One wheel speed sensor is installed on a rear differential detecting rear wheel speed Front wheelsare locked up while heavy braking, vehicle loses its steering stability and stopping distance on alow-μ road surface also increases This system helps vehicle have a straight stop

2.4 ABSCM

ABS consists of wheel speed sensors which detects a wheel lock-up tendency, on the basis ofwheel speed sensor signal a ABSCM(Control Module) which outputs control signal andHCU(Hydraulic Control Unit) which supplies brake pressure to each wheel according to theABSCM output signals

ABSCM(CONTROL MODULE)

From the wheel speed sensor signals, ABSCM calculates an estimated acceleration, decelerationand slip ratio This controls solenoid valves and return pumps to prevent a wheel lock-up.Moreover, ABSCM manages a system monitoring circuit and turn off itself to protect the system if asystem faulty is detected Driver can recognize a system malfunction when ABS warning lampcomes on

1) Basic Composition of ABSCM

Once ABS fails, ABSCM should inhibit the system operation to guarantee the system safety.Because abnormal solenoid valve operation can affect the brake pressure on wheels With thisreason, ABSCM can analyze and prepare all kinds of possible faulty causes

To install the ABSCM directly on the HCU(Hydraulic Control Unit), semiconductors inside ABSCMshould resist at the temperature range of –40 ~ +125 degrees Celsius Owing to the enhancedtechnology on semiconductor and size reduction, Integrated type (ABSCM+HCU) is popularly usedworldwide For example, Bosch ABS version 5.0 or higher, version MK-20i or higher of TEVES andEBC 325 of Kelsey Hayes are representative integrated ABS

All inputs are double-monitored and double-calculated Inputs are also double-monitored.Moreover, to prevent a improper operation of ECU, two microprocessors compare and monitorstheir results And ECU is additionally monitored by SAS(Safety Assurance System) or intelligentWatch-Dog to prevent a ECU’s wrong operation One IC controls solenoids at each channel and aPower MOSFET with a very reliable protect circuit is substituted for relays which handled solenoidoperation and big current while motor operation Furthermore, motor speed control is beingemployed to reduce excessive pumping and Kick-Back 16 bit of microprocessor is used for thebetter ABS performance and wheel speed calculation which requests around 5msec of one cycleoperating time

ABSCM consists of several basic circuits below

a) Wheel Speed Sensor Input Amplification circuit

From each wheel speed sensors installed each wheel, alternating current waveforms in proportion

to the vehicle speed come in the circuit The waveforms are amplified and converted into thesquare waveforms, and are sent to the Microcontroller According to ABS types, the numberofwheel speed sensors changes and the number of amplification circuit also changes

b) Microcontroller

From each wheel speed information, this calculates a Reference Speed, Slip Ratio,Acceleration/Deceleration rates and performs solenoid valve & motor operation This circuit detectsthe wheel speed sensor waveforms generated by the teeth of sensor rotor at every moment.Microcontroller calculates a reference speed by integrating a momentary wheel speed and thencompares the reference speed and a momentary wheel speed to estimate a slip ratio and anacceleration/deceleration rates

Solenoid valve activation circuit outputs pressure dump, hold, increasing signals to the lock-upwheels’ solenoids according to the estimated control signals like a slip ratio, acceleration/deceler-ration rates

c) Solenoid Valve activation circuit

This circuit controls the solenoid valve current and turns it on or off on the basis of the pressuredump, hold, increasing signal from the Microcontroller

d) Voltage Regulator, Motor Relay & Failsafe Relay Driver circuit, Lamp Driver circuit,

Communication circuit

Monitors the supply voltage(5V, 12V) being used for ABSCM is stable within the threshold voltagerange This detects a system failure and activates valve relay, motor relay System faulty isdetected, ABS system is down because a valve/motor relay comes off and ABS warning lamp turns

on to inform the driver of system failure While ABS failure, normal braking is available

ABS ECU Block Diagram

Processor 2 (8bit) Solenoid

Wheel Sensors

ABS W/L EBD W/L

- ABS ECU Block Diagram

Processor 1 (16bit)

Valve Relay

BTCS ECU Block Diagram

IGNITION Voltage

Reg.

Processor 1 (16bit) Processor 2 (8bit)

Solenoid

ABS W/L BTCS Lamp

K-Line EBD W/L

VCC

- BTCS ECU Block Diagram

BLS Wheel Sensors FR Speed Out

8 × Valve Driver 2 × Valve Driver

Valve Relay

2) Safety Circuit

Ignition switch turns on, ABSCM performs a self-test until the vehicle speed reaches certain speedand also monitors system while driving When a system failure is detected, firstly stops the ABSfunction and illuminates ABS warning lamp to inform the driver of system breakdown Even in case

of an ABS breakdown, conventional brake is still available After turn the IG off and turn it on, if asystem faulty is not detected, warning lamp turns off and system comes normal

a) Initial Self-Testing after the IG on,(vehicle stops)

When the IG switch turns on and the voltage comes in ABSCM, followed procedures performs

▪ Microprocessor function check

 Makes an Watchdog Error and check if the error is detected

 Checks the ROM data

 Checks the RAM data whether data reading, writing is normal

 Checks the A/D(Analog /Digital) Converter operation

 Checks the communication between two microprocessor

▪ Valve Relay function check

 Activates a valve relay and check the operation

▪ Fail Memory function check

 Checks the fail memory circuit of a microprocessor

b) Initial Self-Testing while a vehicle begins to move

A vehicle begins to move, ABSCM performs actuators’ function test

▪ Solenoid Valve function test

 Checks the solenoid valve function and monitors its operation

▪ Motor function test

 Operates a motor and check its condition According to the ABS makers, the self-testingtime of motor can be considerably different But mostly, self-testing is performs at thebeginning of vehicle driving or at the end of ABS operation

▪ Wheel Speed Sensor signal check

 Checks whether all wheel speed sensor signals

c) System test while driving

After completing the initial self-test, ABS system is check by two microprocessor and other circuitssurrounding If a faulty is detected, microprocessor finally confirms it and the corresponding errorcode is memorized in ABSCM

▪ Voltage test (12V, 5V)

 Checks the supplied 12 voltage and 5 voltage inside ABSCM is normal But themomentary voltage drop caused by ABS operation or motor operation is considered whilemonitoring 12 voltage

▪ Valve Relay operation test

 While ABS operation, valve relay is activated ABSCM watchdogs a valve relay operation

▪ Calculation Result comparison between two microprocessor

 Usually, there are two microprocessors inside ABSCM and they perform the sameoperation at the same time They compare their results each other and identify theirsameness This comparison concept guarantees the system trust and can detect thesystem failure at an early stage

▪ Microprocessor operation test

 Monitors microprocessor’s normality

▪ ROM Data check

 Performs a Check Sum of ROM data and confirms the program’s normality

d) Display Self Diagnosis

When a system faulty is detected by a safety circuit, ABS function stops illuminating the ABSwarning lamp ABSCM displays trouble codes via a scan tool With the scan tool, activatessolenoid valves and motor

2.5 TYPICAL ABS CONTROL CYCLES

2.5.1 BRAKING CONTROL ON A HIGH-GRIP ROAD SURFACE (HIGH BRAKING FORCE

The speed falls below the threshold(-a) again at the end of phases 3 and a pressure holdphase of a certain length follows The wheel acceleration increases within this time to such anextent that the threshold(+a) is exceeded The pressure remains constant At the end of phases

4, the acceleration exceeds the relatively high threshold(+A) The brake pressure thenincreases as long as the threshold(+A) is exceeded

In phase 6, the brake pressure is kept constant again because the threshold(+a) is exceeded

At the end of this phase, the peripheral wheel acceleration falls below the threshold(+a) This is

an indication that the wheel has entered the stable range of the braking force coefficient/brakeslip curve and is slightly under-braked

The brake pressure is now built up in stages(phase 7) until the wheel deceleration exceeds thethreshold(-a)(end of phase 7) This time, the brake pressure is decreased immediately withoutgeneration of a λ1 signal

2.5.2 BRAKING CONTROL ON A SLIPPERY ROAD (LOW BRAKING FORCE COEFFICIENT)

With this surface condition, slight pressure on the brake pedal is often sufficient to make a

wheel-up on a slippery road and the wheels require much more time to accelerate out of a phase of highslip again

The logic circuit in the ECU recognizes the prevailing road conditions and adapts the ABScharacteristics accordingly

In phase 1 and 2, braking control occurs in the same way as for high braking force coefficients.Phase 3 commences with a pressure holding phase of short duration The wheel speed is thenvery briefly compared with the slip switching threshold λ1 Since the wheel speed is less than thevalue of the slip switching threshold, the brake pressure is reduced for a short, fixed time This isfollowed by a further short pressure hold phase A renewed comparison between the wheel speedand slip switching threshold λ1 is then made, and this leads to a pressure drop during a short, fixedtime period The wheel accelerates again in the following pressure hold phase and its wheelacceleration exceeds the threshold(+a)

This leads to further pressure hold until the acceleration is below the threshold(+a) again (end ofphase 4) This is followed in phase 5 by the step-type build-up in pressure familiar from theprevious section until a new control cycle is initiated by pressure reduction in phase 6 In thepreviously described cycle, the controller logic recognized that a further two pressure decreasesteps were necessary to accelerate the wheel again after the reduction in pressure initiated by the

v F Vehicle speed,

V ref Reference speed,

v

R wheel speed,

λ 1 Slip switching threshold,

signal(-a) The wheel runs in the range of high slip for a relatively long time, and this is not optimalfor driving stability and steerability In order to improve both of these factors, a comparison is madecontinuously between the wheel speed and slip switching threshold λ1 in this and also thefollowing control cycles

Consequently, the brake pressure is constantly reduced in phase 6 until the wheel accelerationexceeds the threshold(+a) in phase 7 Owing to the constant decrease in pressure, the wheel runswith high slip for only a brief period, thus increasing vehicle stability and steerability compared withthe first cycle

v F Vehicle speed,

V ref Reference speed,

v R wheel speed,

λ 1 Slip switching threshold,

- driving force FD caused by the drive,

- lateral force FS caused by the steering, and

- normal force FN as a result of the vehicle weight

The lateral force FS transfers the steering movement to the

road and makes the vehicle turn The normal force FN is

determined by the vehicle weight and its load, that is, it is the

weight component acting perpendicularly on the road The

degree to which the forces can actually come into effect

depends on the condition of the road and tires and on the

weather condition, that is, on the friction force between the

tires and road surface

2.6.2 RELATIONSHIP AMONG FORCES

The relationship between frictional force, side force, braking force and driving force can beexpressed using a “friction circle” The friction circle assumes frictional force between the tire androad surface to be identical in all directions It can be used to visualize the relationship betweenside forces, braking force, and driving force

While cornering at a fixed speed, for example, all of the tire’s frictional force is the side force that isturning the vehicle When brake are applied during cornering, however, part of the frictional force ofthe tire is used for braking force, which reduces the size of the side force Conversely, turning thesteering wheel while applying the brakes reduces braking force, because part of the tire frictionalforce normally used for braking becomes cornering force

<Figure1>

FN

FSF

D

Braking force

Fractional force generated at tire patch

Portion of frictional force

acting as braking force

Cornering force(Fy’)

Cornering

resistance(F Friction force(F)

Side force(Fy)Self aligning torque

i ng

forc

e [kgf]

Cornering forceSide force

The friction FR is proportional to the normal force FN:

FR = μB x FN

The factor μB is the braking force coefficient (or Frictional coefficient) The factor can be influenced

by the characteristics of the different tire/road material pairings The braking force coefficient isthus a measure of the transferable braking force For vehicle tires, the braking force coefficientreaches its maximum values on a dry and clean road surface and its lowest on ice

The braking force coefficient depends greatly on the vehicle speed When braking at high speeds,and under certain road conditions, the wheels may lock if the braking force coefficient is so low thatthe grip of the wheels to the road surface can no longer be available

2.6.6 SLIP

While vehicle driving or braking, complex physical forces occurs in the tire’s contact area with theroad The tire’s rubber elements become distorted and are exposed to partial sliding movements,even if the wheel has not yet locked The measure of the sliding components of the rollingmovement is the slip λ:

λ = (VV - VW)/ VV

 Slip Ratio

Maximum braking force → Approximately 10~30% Slip

This means that some tire rotation is necessary to achieve maximum braking

The optimum slip value decreases as tire-road friction decreases.

<Example>

Road condition Braking force coefficient(μB)Dry concrete 0.8 ~ 1

Wet asphalt 0.2 ~ 0.65Ice 0.05 ~ 0.1

Slip Ratio = (VV - VW)/ VV × 100 VV : Vehicle Speed VW : Wheel Speed

0% → When a tire is rolling freely

100% → When a tire locks up completely

Tire shape when vehicle is cornering

Where Vv is the vehicle speed and VW is the circumferential speed of the wheel

The formula shows that brake slip occurs as soon as the wheel starts to rotate more slowly thanthe wheel speed which corresponds to the driving speed Braking forces can be generated only inthis condition

Figure 1 [Braking force coefficient as a function of brake slip for straight-ahead braking] applies to

straight-ahead braking where no lateral forces occur so that the whole friction available betweenthe tire and road surface can be used for braking The braking force increases steeply from a brakeslip zero, and reaches its maximum between about 10% and 30% brake slip, depending on theroad and tire conditions The rising part of the curves shows a stable area, while the falling partrepresents the instable area When driving straight ahead, ABS prevents a vehicle entering thisinstable area during braking

2.6.7 LATERAL FORCE (SIDE FORCE)

In addition to the braking force and driving force acting on the contact area in the direction that thetire is rotating, there is also a “Lateral force” that acts laterally on the tire Side force is the basicforce that occurs when the vehicle turns The basic force during cornering by a vehicle is the force

of the part of the tire in contact with the road surface wanting to return its normal shape from itscurrently deformed state This force pushes the tire sideways against the road surfaces, and istherefore called “Side force” And the moment generated at the deformed tire is called “ Overturning moment

2.6.8 UNDERSTEERING AND OVERSTEERING

Keeping the steering wheel turned at a fixed angle and traveling at a fixed speed causes thevehicle to move in a circle with a fixed radius Increasing the vehicle’s speed at this point causesthe vehicle to move either outside the original circle due to “Understeering”, or inside the originalcircle due to “Oversteering” The actual steering characteristic (Understeering or Oversteering)produced by a particular vehicle depends on the interrelationship between the weight distributionbetween its front and rear wheels, tire specifications, suspension characteristics, and drive system (FF or AWD)

Tire shape when vehicle

is traveling straight

2.6.9 BRAKING FORCE COEFFICIENT AS A FUNCTION OF BRAKE SLIP FOR

STRAIGHT-AHEAD BRAKING

2.6.10 BRAKING FORCE AND LATERAL FORCE COEFFICIENT AS A FUNCTION OF BRAKE

SLIP

2.6.11 BRAKING FORCE AND LATERAL FORCE COEFFICIENT AS A FUNCTION OF BRAKE

SLIP AND SLIP ANGLE α WITH ABS CONTROL RANGES

1.Radial tires on dry concrete2.Bias-ply tires on wet asphalt3.Radial tires on snow:

(a lock-up wheel pushes a wedge of snow in front of it which increases the braking force.)

4.Radial tires on wet ice(Ice to freezing point)

a: Stable range b: Unstable range A: No slip (Free rolling) B: 100% slip (Blocked)

The lateral force coefficient is themaximum value when a brake slip is zero.With increasing brake slip, it falls slowlyreaching the lowest point when the wheel

Center point

During curve braking, the braking forces increases so quickly that the overall braking distance isonly slightly longer than for straight-ahead braking under the same condition.

2.7 SELECT LOW CONTROL FOR THE REAR WHEEL

Most vehicle with ABS system, whether it has a 4-channel system or a 3-channel system,incorporates a Select Low Control logic for rear wheels while ABS operation That’s because toguarantee the vehicle stability which can be easily obtained by avoiding the rear wheel lock-up.One of the ABS benefits is to get an optimal braking force at all kinds of road conditions and abraking situation For this, independent control of the front wheels is necessary Because, firstly,front wheels generate almost 70 % braking power while braking, therefore independent control canprovide a short stopping distance while ABS control Secondly, uneven grip of each front wheeldoesn’t make a serious vehicle stability problem while ABS operation comparing with the problemfrom rear wheels

ABS control ranges

As the two curves for braking forcecoefficient μB and lateral force coefficient

μS, the ABS control range must beextended for larger slip angle α = 10˚ (that

is high lateral force owing to high lateralacceleration of the vehicle) compared withthe small slip angle α = 2˚

The ABS permits increasingly greater slipvalues in accordance with the degree bywhich the speed and thus lateralacceleration decrease during lateralbraking

When there is a differential in braking force between the left and right tires, the vehicle tends toswerve in the direction of the stronger

braking force When there is uneven

left-right braking force in the front

wheels, the vehicle can be kept in a

straight line relatively easily by turning

the steering wheel

In the case of rear wheels, however, it

is much difficult to compensate for

left-right braking force differential by

turning the steering wheel, so vehicle

handling become quite unstable

To counteract this, ABSCM reduces

the brake pressure to the other rear

wheel as well as rear wheel beginning

to lock This maintains the side force of

the tires are their current levels while

equalizing the left-right braking force to

provide better stability

2.8 ABS GENERAL CONSTRUCTION

Uneven braking forceHigh frictional surface Low frictional surface

Equal braking force

ABS/TCS/ESP TRAINING GUIDE

When the Tone Wheel rotates, the magnetic field changes and induces a voltage in the winding

- Permanent magnetic ▶ produce a voltage

- Higher speeds ▶ produce a higher frequency

- Lower speeds ▶ produce a lower frequency

2.10 FEATURE OF G-SENSOR

ABS control for 4WD uses the signal of G-sensor to solve the problems that is early all wheel-lock

on Lm and that late response in case of m change of road surface G-sensor signal is got every7ms, and filtered ABSCM sets m-flags (High, Medium, Low) to calculate detailed gradient ofreference velocity and control threshold compared with 2WD

2.10.1 GENERAL SPECIFICATION

Operating voltage DC 8 ~ 16 V

Operating temperature range -30°C ~ +85°C

Storage temperature range -40°C ~ +100°C

Current consumption 10 mA MAX

2.10.2 G SENSOR OPERATION

The four wheels of an AWD(All Wheel Drive)/4WD vehicle are linked by the center differential, sothe engine brake acts on all the wheels Because of this, in case that any of the tires of an AWDvehicle begin to lock-up, the control torque of the tire that is beginning to lock-up is distributed tothe other tires, making the rotation speed of all the tires virtually identical Since the signal beingsent to the ABSCM from the four ABS sensors at this time are almost similar, the reference vehiclespeed calculated by the ABSCM is less than actual vehicle speed Using the calculated result as abasis for ABS control would result in error that would increase the danger of wheel lock-up

In order to overcome the problem described above, an AWD vehicle is equipped with a G sensor,which is used to determine the friction between tires and the road surface For example, if a driverslams the brake pedal on the ice making all wheels lock-up, the vehicle begin to slide and the G

WAVE FORM 3 (At high speed)

value(deceleration) will be low Because all wheels lost their grip on the the ice and they cannotmake a frictional force which increase the G value Therefore the ABSCM can recognize all wheellock-up tendency by referring to the low G value In other case, even if all wheel speed is reducedbecause of one wheel or two wheels’ lock-up, if the G sensor value remains high, ABSCM correctsthe reference vehicle speed that comes from only wheel speed information So, ABS control can bemore accurate.

2.10.3 G SENSOR FUNCTION FOR 4WD VEHICLE

When driving in 4WD, all four wheels are mechanically locked, so all wheel speed decrease withalmost same rate in many case This phenomenon is more notable when driving on low μ(friction)road, so ABS control become unstable To prevent this happening, G sensor is installed

With this signal, ABSCM recognize that the vehicle is now stopping on a low μ road or high μroad, thereby modifying the ABS operating cycle(algorism) That is,

Small(or Great) G braking → G value Low (or High) → Low (or High) μ road detected → ABSCMadvances(or delays) to decrease hydraulic pressure → Wheel lock is delayed(or advanced) →Stopping distance increases(or Decreases)

2.10.4 INSTALLATION

Install the G-sensor with the arrow mark facing forward direction

2.10.5 SENSOR INSPECTION

38 Chonan Technical Service Training Center

[Top view]

1 Connect a T-connector to the G-sensor and check the voltage

2 Turn ‘IG ON’ and check the output voltage of G-sensor on the plane

▪ Standard value: 2.5 V

3 Measure the output voltage while leaning the sensor forward or backward And make sure theoutput value varies normally

▪ Regarding sensor output characteristic, refer to

the graph next slide

Dummy vehicle speed When G sensor is not equipped

Vout (V)

4.003.503.252.501.751.501.25

-14.7[-1.5] -9.80[-1]

-90°

-7.35[-0.75]

-48.6°

0[0]

0°

+7.35[+0.75]

48.6°

+9.80[+1]

90°

+14.7[+1.5] Acceleration (m/s

2)Acceleration (G)Angle (°)

2.11 SYSTEM LINE-UP