Anti Lock Braking System (ABS) of cars

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PROJECT

PROJECT

REPORT

REPORT

A

A

NTI

NTI

-

-

LOCK

LOCK

B

B

RAKING

RAKING

S

S

YSTEM

YSTEM

SUBMITTED

SUBMITTED BY:

BY:

SUBMITTED

SUBMITTED TO:

TO:

NS

NS BILAL

BILAL WASEEM

WASEEM

SIR

SIR AKHTAR

AKHTAR KHURSHID

KHURSHID

NS ESAAM JAMIL

NS ESAAM JAMIL

NS

NS SOHAIL

SOHAIL TANVEER

TANVEER

SUBJECT:

SUBJECT:

NS

NS BILAL

BILAL TAHIR

TAHIR

CONTROL SYSTEMS

CONTROL

SYSTEMS

NS HAFIZ M. NOUMAN 

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1.

1.

ACKNOWLEDGEMENT:

ACKNOWLEDGEMENT:

F

First of all thanks to Allah Almighty who has given human beings brilliantirst of all thanks to Allah Almighty who has given human beings brilliant

minds and made us the crown of the creation. minds and made us the crown of the creation.

Secondly, we would like to honor our respected sir Akhtar Khurshid for his Secondly, we would like to honor our respected sir Akhtar Khurshid for his advice and encouragement in making this project. We would also like to thank advice and encouragement in making this project. We would also like to thank him for always being available for our guidance and help inside and outside him for always being available for our guidance and help inside and outside the class.

the class.

F

Finally, we would like to thanks our parents for their love. We would alsoinally, we would like to thanks our parents for their love. We would also

like to acknowledge with appreciation of their support in our studies. like to acknowledge with appreciation of their support in our studies.

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TABLE

TABLE OF

OF CONTENTS:

CONTENTS:

TOPICS

TOPICS

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                                   

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INTRODUCTION:

INTRODUCTION:

An

An Anti-LockAnti-Lock brabrakingking syssystemtem ((ABS)ABS) is a safety system on motor vehiclesis a safety system on motor vehicles which prevents the wheels from locking while braking.

which prevents the wheels from locking while braking.

The Anti-lock Braking System is designed to maintain vehicle control, The Anti-lock Braking System is designed to maintain vehicle control, directional stability and optimum deceleration under severe braking conditions on directional stability and optimum deceleration under severe braking conditions on most road surfaces

most road surfaces

It does so by monitoring the rotational speed of each wheel and controlling It does so by monitoring the rotational speed of each wheel and controlling the brake line pressure to each wheel during braking. This prevents the wheels the brake line pressure to each wheel during braking. This prevents the wheels from locking up.

from locking up.

A rotating road wheel allows the driver to maintain steering control under A rotating road wheel allows the driver to maintain steering control under heavy braking.

heavy braking.

4.

4.

HH

ISTORY:

ISTORY:

19

192299 Anti-lock braking systems were first developed for aircraft, by Gabriel Voisin.Anti-lock braking systems were first developed for aircraft, by Gabriel Voisin.

195

19500 Dunlop's Maxaret introduced a system and still in use on some aircraftDunlop's Maxaret introduced a system and still in use on some aircraft

models. models. 196

19600 A fully mechanical system used in theA fully mechanical system used in the FFerguson P99 racing car, the Jensenerguson P99 racing car, the Jensen FFFF

and the

and the FFord Zodiac, but saw no further use; the system proved expensive and, inord Zodiac, but saw no further use; the system proved expensive and, in

automobile use, somewhat unreliable. automobile use, somewhat unreliable. 196

19644 Limited form of ABS in Austin 1800, utilizing a valve which could adjust frontLimited form of ABS in Austin 1800, utilizing a valve which could adjust front

to rear brake force distribution when a wheel locked. to rear brake force distribution when a wheel locked. 1971

1971 Chrysler and Bendix Corporation introduced imperial called "Sure Brake".Chrysler and Bendix Corporation introduced imperial called "Sure Brake". 1971

1971 ABS Systems based Mercedes design were later introduced on other cars.ABS Systems based Mercedes design were later introduced on other cars. 1975

1975 FFord also introduced ABS on the Lincoln Continental Mark III and theord also introduced ABS on the Lincoln Continental Mark III and the FFordord

LTD station wagon, called "Sure Trak LTD station wagon, called "Sure Trak 1978

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4-wheel multi-channel ABS system in trucks and the Mercedes-Benz S-Class. wheel multi-channel ABS system in trucks and the Mercedes-Benz S-Class. 1988

1988 BMW became the world's first motorcycle manufacturer to introduce anBMW became the world's first motorcycle manufacturer to introduce an electronic/hydraulic ABS system, this on their BMW K100.

electronic/hydraulic ABS system, this on their BMW K100. 199

19922 Honda launched its first ABS system, this on the ST1100 Pan European.Honda launched its first ABS system, this on the ST1100 Pan European.

1997

1997 Suzuki launched its GSSuzuki launched its GSFF1200SA (Bandit) with ABS.1200SA (Bandit) with ABS.

Today ABS has become standard equipment even for small cars. Today ABS has become standard equipment even for small cars.

5.

5.

INSPIRATIONS

INSPIRATIONS BE

BE

HH

IND ABS:

IND

ABS:

The basic design of a braking system has been around and in use in other The basic design of a braking system has been around and in use in other applications for many years. The brakes in a car use the simple principle of  applications for many years. The brakes in a car use the simple principle of  hydraulics. This principle reduces the amount of work required by the user.

hydraulics. This principle reduces the amount of work required by the user. FFigureigure

below illustrates the basic design of a modern braking system. below illustrates the basic design of a modern braking system.

F

Figure: Basic braking system designigure: Basic braking system design

The problem with the traditional braking system is that the force exerted by The problem with the traditional braking system is that the force exerted by the brakes on the wheel cannot exceed the force of friction between the wheel the brakes on the wheel cannot exceed the force of friction between the wheel and the road. If the braking force exceeds the force of friction from the road the and the road. If the braking force exceeds the force of friction from the road the vehicle will begin to slide. This problem brought about the invention of the vehicle will begin to slide. This problem brought about the invention of the

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anti-locking breaking system (ABS). The ABS detects drastic changes in the speed of  locking breaking system (ABS). The ABS detects drastic changes in the speed of  the wheels. When a sharp deceleration is detected the ABS will reduce the the wheels. When a sharp deceleration is detected the ABS will reduce the hydraulic pressure supplied to the braking system until the wheel begins to hydraulic pressure supplied to the braking system until the wheel begins to accelerate again. When the acceleration is detected the pressure is again accelerate again. When the acceleration is detected the pressure is again increased until an unusual amount of deceleration is detected. The process is increased until an unusual amount of deceleration is detected. The process is repeated until the user removes their foot from the brake pedal or the vehicle repeated until the user removes their foot from the brake pedal or the vehicle comes to a complete stop.

comes to a complete stop.

6.

6.

BASIC

BASIC COMPONENTS

COMPONENTS OF

OF ABS

ABS AND

AND T

T

HH

EIR

EIR FUNCTIONS:

FUNCTIONS:

The ABS consists of speed sensors, valves, a pump, and a controller. The The ABS consists of speed sensors, valves, a pump, and a controller. The location of these devices within a vehicle is shown in figure below:

location of these devices within a vehicle is shown in figure below:

F

Figure: Anti-Lock Braking System Designigure: Anti-Lock Braking System Design

a

a)) SPEED

SPEED SENSORS:

SENSORS:

The speed sensor is used to determine the acceleration The speed sensor is used to determine the acceleration or deceleration of the wheel. A picture of this sensor is or deceleration of the wheel. A picture of this sensor is shown in figure right:

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These sensors use a magnet and a coil of wire to generate a signal. The These sensors use a magnet and a coil of wire to generate a signal. The rotation of the wheel or differential induces a magnetic field around the sensor. rotation of the wheel or differential induces a magnetic field around the sensor. The fluctuations of this magnetic field generate a voltage into the sensor. A The fluctuations of this magnetic field generate a voltage into the sensor. A schematic of this system is shown in figure below. The ABS controller interprets schematic of this system is shown in figure below. The ABS controller interprets this signal.

this signal.

F

Figure: Speed Sensor Schematicigure: Speed Sensor Schematic

Since the voltage inducted on the sensor is a result of the rotating wheel, this Since the voltage inducted on the sensor is a result of the rotating wheel, this sensor can become inaccurate at slow speeds. The slower rotation of the wheel sensor can become inaccurate at slow speeds. The slower rotation of the wheel can cause inaccurate fluctuations in the magnetic field and thus cause inaccurate can cause inaccurate fluctuations in the magnetic field and thus cause inaccurate readings to the controller.

readings to the controller.

b

b))

VV

AL

AL

VV

ES:

ES:

The valves within an ABS serve three distinct functions. The first function of  The valves within an ABS serve three distinct functions. The first function of  the valves is to open and allow the hydraulic fluid from the brake pedal or the the valves is to open and allow the hydraulic fluid from the brake pedal or the pump to reach the braking system. The second function of the valves is to pump to reach the braking system. The second function of the valves is to maintain the current pressure provided to the braking system. This is maintain the current pressure provided to the braking system. This is accomplished by closing the valve to resist further pressure from the brake accomplished by closing the valve to resist further pressure from the brake pedal. The third function of these valves is to reduce the amount of hydraulic pedal. The third function of these valves is to reduce the amount of hydraulic pressure at the braking system. This is accomplished by opening the valves to pressure at the braking system. This is accomplished by opening the valves to allow the hydraulic fluid to be released from the braking system. A picture of a allow the hydraulic fluid to be released from the braking system. A picture of a standard ABS valve and pumping system is show in figure below.

standard ABS valve and pumping system is show in figure below.

The majority of problems with the valve system occur due to clogged The majority of problems with the valve system occur due to clogged valves. When a valve is clogged it is unable to open, close, or change position. valves. When a valve is clogged it is unable to open, close, or change position.

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An inoperable valve will prevent the system from modulating the valves and An inoperable valve will prevent the system from modulating the valves and controlling pressure supplied to the brakes.

controlling pressure supplied to the brakes.

F

Figure: ABS Valves and Pumping Systemigure: ABS Valves and Pumping System

c)

c) PUMPS:

PUMPS:

The pump in the ABS is used to restore the pressure to the hydraulic brakes The pump in the ABS is used to restore the pressure to the hydraulic brakes after the valves have released it. A signal from the controller will release the valve after the valves have released it. A signal from the controller will release the valve at the detection of wheel slip. After a valve release the pressure supplied from the at the detection of wheel slip. After a valve release the pressure supplied from the user, the pump is used to restore a desired amount of pressure to the braking user, the pump is used to restore a desired amount of pressure to the braking system. The controller will modulate the pumps status in order to provide the system. The controller will modulate the pumps status in order to provide the desire amount of pressure and reduce slipping. A picture of the pumping system desire amount of pressure and reduce slipping. A picture of the pumping system is shown in figure above.

is shown in figure above.

Similar to the valves, the major limitation or mode of failure is due to blockage Similar to the valves, the major limitation or mode of failure is due to blockage within the pump. A blockage within the pump will prevent the pump from within the pump. A blockage within the pump will prevent the pump from supplying the correct pressure to the pumping system

supplying the correct pressure to the pumping system.. d

d

)) CONTROLLER:

CONTROLLER:

The entire system is observed and manipulated by the ABS controller. A The entire system is observed and manipulated by the ABS controller. A detailed control system used in ABS is shown in figure below.

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F

Figure: ABS Control Systemigure: ABS Control System

7.

7.

MAT

MAT

HH

EMATICAL MODELLING

EMATICAL

MODELLING AND

AND TRANSFER

TRANSFER

FUNCTIONS:

FUNCTIONS:

The parts described above produce the control loop shown in figure below: The parts described above produce the control loop shown in figure below:

F

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F

For the purpose of the analysis the pump and valves will be combined inor the purpose of the analysis the pump and valves will be combined in

the system to form the actuator and the controller will be modified to a P, PD, or the system to form the actuator and the controller will be modified to a P, PD, or a PID controller. The control loop shown in figure below will be used for the a PID controller. The control loop shown in figure below will be used for the remainder of the analysis.

remainder of the analysis.

F

Figure: Control Loop Evaluated for the ABSigure: Control Loop Evaluated for the ABS

The basic equation of rotational motion will be used to evaluate the plant. The basic equation of rotational motion will be used to evaluate the plant. This formula is shown below in Equation 1.

This formula is shown below in Equation 1.

Where J is the moment of inertia of tire about the axis of rotation Where J is the moment of inertia of tire about the axis of rotation



 is the angular acceleration of the tireis the angular acceleration of the tire

is the angular velocity of the tireis the angular velocity of the tire

b is the rotational damping of the tire (bearings). b is the rotational damping of the tire (bearings).

F

For the purpose of this analysis the values below will be used:or the purpose of this analysis the values below will be used:

Tire Weight = 75 Kg Tire Weight = 75 Kg Tire Radius = 33 cm Tire Radius = 33 cm

F

From these values the moment of inertia is calculated to be J = 4.1 Kg*m^2.rom these values the moment of inertia is calculated to be J = 4.1 Kg*m^2.

Since the wheel has bearing and the bearings are well lubricated the assumption Since the wheel has bearing and the bearings are well lubricated the assumption is that the rotational damping factor is b = 1. Equation 2, Equation 3, and Equation is that the rotational damping factor is b = 1. Equation 2, Equation 3, and Equation 4 show how the equation above is converted into a transfer function with the 4 show how the equation above is converted into a transfer function with the appropriate J, b, and

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Laplace

Laplace((EquationEquation11)) == J  J [[ss((ss))  ( (00)])] ++ bb((ss)) == T ((ss))

Where

Where  (0) is the initial angular velocity(0) is the initial angular velocity

The valves and pumping system are combined in this analysis to represent The valves and pumping system are combined in this analysis to represent the actuator. The actuator can be modeled as a servo system. The servo system the actuator. The actuator can be modeled as a servo system. The servo system has the transfer function shown in Equation 5.

has the transfer function shown in Equation 5.

The same values used to define Equation 4 are valid for Equation 5. The same values used to define Equation 4 are valid for Equation 5. Equation 6 is the servo motor transfer function with the appropriate values for Equation 6 is the servo motor transfer function with the appropriate values for the rotational damping and the moment of inertia.

the rotational damping and the moment of inertia.

The sensor used for the ABS application converts the velocity of the The sensor used for the ABS application converts the velocity of the rotating wheel into a voltage. This application can be modeled as a tachometer. rotating wheel into a voltage. This application can be modeled as a tachometer. Equation 7 is the transfer function of a tachometer.

Equation 7 is the transfer function of a tachometer.

The new control loop obtained from the transfer functions above is shown The new control loop obtained from the transfer functions above is shown in figure below.

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F

Figure: ABS Control Loop Including System Transferigure: ABS Control Loop Including System Transfer FFunctionsunctions

The controller in the revised control loop is then tested under P, PD, and The controller in the revised control loop is then tested under P, PD, and PID control. In the analysis the gain of the sensor (Ktach) is assumed to be 25. This PID control. In the analysis the gain of the sensor (Ktach) is assumed to be 25. This assumption is based on the fact that the voltage produced by the sensor is small. assumption is based on the fact that the voltage produced by the sensor is small. The controller will require a higher voltage signal in order to receive the The controller will require a higher voltage signal in order to receive the information from the sensor. Therefore the voltage from the sensor must be information from the sensor. Therefore the voltage from the sensor must be amplified and thus the gain is high. The gain of the actuator (Kact) is assumed to amplified and thus the gain is high. The gain of the actuator (Kact) is assumed to be 0.25 in the controller analysis. This is due to the high pressures of the hydraulic be 0.25 in the controller analysis. This is due to the high pressures of the hydraulic system. The valve and pumping system will not have to do much work in order to system. The valve and pumping system will not have to do much work in order to achieve the desired pressures at the braking system.

achieve the desired pressures at the braking system.

The results of the P control analysis are shown in figures below. In first The results of the P control analysis are shown in figures below. In first figure the proportional gain (Kp) is 1000 and the transfer function shown in figure the proportional gain (Kp) is 1000 and the transfer function shown in Equation 8 is used. In latter figure the proportional gain (Kp) is 1 and the transfer Equation 8 is used. In latter figure the proportional gain (Kp) is 1 and the transfer function shown in Equation 9 is used. As seen in the graphs, the braking effects function shown in Equation 9 is used. As seen in the graphs, the braking effects are liner with a higher proportional gain. When Kp is reduced the braking pattern are liner with a higher proportional gain. When Kp is reduced the braking pattern is non-linear. The non-linear results are due to slipping.

is non-linear. The non-linear results are due to slipping.

F

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F

Figure: ABS Proportional Control w/ Kp = 1000igure: ABS Proportional Control w/ Kp = 1000

F

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The results of the PD control analysis are shown in figure below and the The results of the PD control analysis are shown in figure below and the results of the PID control analysis are shown in last figure. These graphs show that results of the PID control analysis are shown in last figure. These graphs show that linear braking can be achieved through the use of PD and PID control.

linear braking can be achieved through the use of PD and PID control.

F

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F

Figure: igure: ABS Proportional, ABS Proportional, Derivative, and IntDerivative, and Integral Controlegral Control

8.

8.

CONCLUSION/DISCUSSION:

CONCLUSION/DISCUSSION:

The control analysis shows that a proportional (P), proportional / derivative The control analysis shows that a proportional (P), proportional / derivative (PD), and the proportional / Integral / Derivative (PID) is able to control the ABS. (PD), and the proportional / Integral / Derivative (PID) is able to control the ABS. Since all of the control systems will achieve the desired results, the best design Since all of the control systems will achieve the desired results, the best design must be determined by another method. Since the proportional control is the must be determined by another method. Since the proportional control is the least complex, the ABS controller should use this method. The ABS is responsible least complex, the ABS controller should use this method. The ABS is responsible for preventing car accidents and personal injury. A simplified system should for preventing car accidents and personal injury. A simplified system should reduce the complexity, cost, as well as increase the easy of serviceability.

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9.

9.

REFERENCES:

REFERENCES:

Online resources for ABS Braking Systems Online resources for ABS Braking Systems Georgia Institute of Technology

Georgia Institute of Technology

George W. Woodruff School of Technology

George W. Woodruff School of Technology

Article Introduction and History Article Introduction and History www.scribd.com

www.scribd.com

Motorola

Motorola for the article Anti-Lock Braking Systemsfor the article Anti-Lock Braking Systems

http://www.motorola.com/webapp/sps/site/application.jsp?nodeId=04M0ym4Ky

http://www.motorola.com/webapp/sps/site/application.jsp?nodeId=04M0ym4Ky

5P

5P

Controls Tutorial for Matlab Controls Tutorial for Matlab

http://www.engin.umich.edu/group/ctm/index.html

http://www.engin.umich.edu/group/ctm/index.html

How Stuff Works for the article

How Stuff Works for the article How Anti-Lock Brakes Work How Anti-Lock Brakes Work 

http://www.howstuffworks.com/

http://www.howstuffworks.com/

Magneto-Resistive Wheel Speed Sensors, New Active Wheel Speed Sensors Magneto-Resistive Wheel Speed Sensors, New Active Wheel Speed Sensors Changing ABS Diagnostic Procedures, David W. Gilbert.

Changing ABS Diagnostic Procedures, David W. Gilbert. http://www.asashop.org/autoinc/aug2001/mech.cfm

http://www.asashop.org/autoinc/aug2001/mech.cfm

Heavy Truck Pneumatic Braking System Modeling, Analysis and Anti-lock Braking Heavy Truck Pneumatic Braking System Modeling, Analysis and Anti-lock Braking Robust Controller Design, Prof. Umit Ozgumer.

Robust Controller Design, Prof. Umit Ozgumer.

http://car.eng.ohio-state.edu/consortium/proposals/hdv/h02pneu.pdf 

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