Anti Brake System

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Software Requirement Specification

Automobile Anti braking System Design

Software Requirements Specification

Version

Auhor: Renu Shinde , SKNCOE, M.E.(I. T.), Pune

Issue Date: 15/10/2011

Document Class:


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Document Revision History

Date Version Description Author

05/10/2011 Detail of system requriment specification Renu Shinde

SKNCOE, M.E.(I. T.)

13/10/2011 Detail of system requirement specification Renu Shinde

SKNCOE, M.E(I.T)

Approvals

Name Role Date

Prof. L.V.Patil SEM-FACULTY MEMBER 15/10/2011


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Table of Contents

1. Introduction

1.1 Purpose of project

1.2 Scope

1.3 Definitions, Acronyms and Abbreviations:

1.4 References

1.5 Business Overviews

2. Overall Description2.1 Product perspective

2.2 Product functions

2.3 User characteristics

2.4 Constraints

2.5 Assumptions

2.6 Dependencies

3. System Objectives

3.1 Functional Requirements.

3.2 Non-Functional Requirements.

3. 3 Design constraints.


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1. Introduction

1.1. Purpose of project

The purpose of this project is to develop a safety system that allows thewheels on a motor vehicle to continue interacting tractively with the road

surface as directed by driver steering inputs while braking , preventing the

wheels from locking up and therefore avoiding skidding.

This system is meant to provide the security for cars, two wheelers, heavyloaded vehicles etc.

1.2 Scope

The main objective of this project is to design, construct and test an

automobile based anti brake system, that can be used to provide a high level of

security and security to the driver by preventing the wheels from locking , which

maintains directional stability. An antilock brake system provides a high level of

safety to the driver by preventing the wheels from locking which maintains directional

stability. A professional driver may be capable of modulating the brakes

approximately once per second, ABS is capable of modulating the brakes pressure at a

given wheel up to fifteen times per second. An ABS system does the same things than

a professional driver can do , it controls each front brake separately and the rear

brakes as a pair whenever one of the wheels start to lock.

In order to carry out the objectives of the project , the following works were carried

out.

Design and development of speed sensors. Design and development of valves. Design and development of pump. Design and development of Controller.


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1.3 Definitions, Acronyms, and Abbreviations

Acronym Description

ABS Anti Brake System

ECU Electronic Control Unit

EBD ElectronicBrakeforce

Distribution

ESC Electronic Stability Control

TCS Transaction Control System

CBC Concerning Brake Control

1.4 Reference Antilock Brake System With a Continuous Wheel Slip Control

to Maximize the Braking Performance and the Ride Quality by

Choi, S.B at Grad. Sch. of Automobile Technol., Korea Adv.

Inst. of Sci. & Technol., Daejeon in issue 5 in volume 16,

year sept 2008

Anti-lock braking system simulation and modelling in ADAMSby Ozdalyan, B.; Blundell, M.V at Sch. of Eng., Coventry

Univ, year sept 2009

1.5 Business Overviews

All of us must have faced a situation many times in our

lives when driving even at a relaxed pace, you had to stomp on braking

due to sudden arrival of an object in front of us or simply because of a

deep pothole or speed breaker above average height. What is the common

thinking in such situations? Simply thrash the brake padel with full force. But in


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most of the cases, the vehicles refuse to stop in time and keep skidding and/or

sliding and also all of a sudden, the steering and/or handle also get so tight that we

could not steer the car away from the object and eventually end up in crashing in or

on a pothole or a speed breaker or hit an object. Efforts failed, result met. In worse

cases, if the object was big or we were at speeds above than normal, it did also

pose risk to our life. In fact most of the accidents, take place due to head on crash

for which, failure in stopping power is responsible. In most of these cases, the

accident could have been avoided if the car was able to be stopped just a feet or so

before the point of collision.Based onthese reasons it is necessary for the design

and development of Anti- Brake System in an automobile to make human lives

more and more secure.

Below are the two diagrams that shows us, how an ABS system can help human

lives to control an accident.

Figure 1.1: The left car is without the ABS and the right car is with ABS


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Figure 1.2 : An abs installed in a two wheeler can be more secure.


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2. Overall Description

2.1. Product Perspective:

The proposed system is Automobile Anti Braking System. It can be work in the

following way.

I: Speed Sensors

II: Valves

III.Pump

IV.Controller

V.User automobile

2.2 Product Function

Product can be perform following types of functions.

Speed Sensors:

The anti-lock braking system needs some way of knowing when a

wheel is about to lock up. The speed sensors, which are located at each wheel, or in

some cases in the differential, provide this information.

Valves:

There is a valve in the brake line of each brake controlled by the

ABS. On some systems, the valve has three positions:

In position one, the valve is open; pressure from the master cylinder is passed rightthrough to the brake.

In position two, the valve blocks the line, isolating that brake from the mastercylinder. This prevents the pressure from rising further should the driver push the

brake pedal harder.

In position three, the valve releases some of the pressure from the brake.


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Pump

Since the valve is able to release pressure from the brakes, there has to

be some way to put that pressure back. That is what the pump does; when a valvereduces the pressure in a line, the pump is there to get the pressure back up.

Controller

The controller is an ECU type unit in the car which receives

information from each individual wheel speed sensor, in turn if a wheel loses traction

the signal is sent to the controller, the controller will then limit the brake force (EBD)

and activate the ABS modulator which actuates the braking valves on and off.

2.3 User Characteristics

User may be male or female. It acts as the owner of the system. The end user can be the driver of the car, or the admin of the car. The system is interacting with owner of the car.

2.4 Constraints

There are different ways in which a an ABS system works. The one

simple system is given below.

The controller monitors the speed sensors at all times. It is looking for decelerations

in the wheel that are out of the ordinary. Right before a wheel locks up, it will

experience a rapid deceleration. If left unchecked, the wheel would stop much more

quickly than any car could. It might take a car five seconds to stop from 60 mph

(96.6 km/h) under ideal conditions, but a wheel that locks up could stop spinning in

less than a second.

1. The ABS controller knows that such a rapid deceleration is impossible, so it reducesthe pressure to that brake until it sees an acceleration, then it increases the pressure

until it sees the deceleration again. It can do this very quickly, before the tire can

actually significantly change speed. The result is that the tire slows down at the same

rate as the car, with the brakes keeping the tires very near the point at which they will

start to lock up. This gives the system maximum braking power.


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2. When the ABS system is in operation the driver will feel a pulsing in the brake pedal;this comes from the rapid opening and closing of the valves. This pulsing also tells

the driver that the ABS has been triggered. Some ABS systems can cycle up to 16

times per second

2.5 Assumptions & dependencies:

The following assumptions are made in anti lock breaking system:

1. The speed sensors should determine the acceleration or deacceleration ofwheels.

2. The valves should provide three functions.i)It should maintain the current pressure provided to the braking

system.

ii) It should reduce the amount of hydraulic pressure at the breaking

system.

iii) It should open and allow the hydraulic fluid from the brake pedal

or the pump to reach the braking system.

3 .The pump should provide following functions.

The pump in the ABS is used to restore the pressure to the hydraulic

brakes after the valves have released it

4.The entire system should be observed and manipulated by the ABS

controller.


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3.System Objectives3.1. Functional Requirements

This section gives the list of functional and non functional

requirements which are applicable to Automobile anti brake system. Functional

requirements are nothing but the services provided by the system to its users. The

services provided to the users by means of following concepts.

1.Brake control module.

2.Solenoid valve assembly.

3.Speed sensors.

4.Wiring and the amber ABS brake warning light.

3.1.1 Brake Control Module: The brake control module is a compute that receives

information from the speed sensor and compares it to the

speed of other wheels.

When one wheel is approaching lock-up pressure can bevented allowing the wheel nearing lock-up to speed up.

The brake control module is a compute that receivesinformation from the speed sensor and compares it to the

speed of other wheels.

When one wheel is approaching lock-up pressure can bevented allowing the wheel nearing lock-up to speed up.

3.1.2 Solenoid valve assembly

Is a pair of valves that can:

Increase pressure Hold pressure steady Decrease pressure


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3.1.3 Speed sensorsBasically there are sensors at each of the four wheels. These sensors

watch the rotation of the wheels, when any one of the wheels stops rotating due to too

much brake application, the sensors tell the cars computes which then releases some

of the brake line pressure that we have applied-allowing the wheel to turn again.

Then, just as it released the pressure , the computer allows the pressure to be applied

againwhich stops the rotation of the wheel again. Then it releases again and so on.

3.1.4 ABS brake warning light

When a fault occurs in the signal transmission system, the ABS

warning light and brake warning light in the combination meter come on. At the same

time ,the current to the hydraulic control unit is interrupted . The brake system then

functions in the same manner as a system without without ABS. The warning light

utilizes a dual circuit design.

Figure 3.1: ABS warning light


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3.2 Non functional Requirements

The non functional requirement of the system are:

Performance: performance is a combination of softperformance metrices such as approximate time to perform

a user level function and hard deadlines by which a

particular operation , here for example applying the brakes,

must be completed.

Cost: the target cost or purchase price for the system isalmost always a consideration. Cost typically has two major

components: manufacturing cost includes the cost of

components and assembly ; nonrecurring engineering

(NRE) costs include the personnel and other costs of

designing the system.

3.3 Design constraints

Constraints to the anti-lock braking system include the following:

The wheel speed sensor gives input to the controller. Rapiddeceleration causes the ABS system to start. The system

must check for skidding hundreds of times a second. If one

wheel is decelerating faster than the others, lockup can be

caught before it happens.

The system must need to control a value that interfaceswith the wheel cylinders. It results in 'pumping' of the

brakes, as much as 10 times per second.

This relieving of pressure which occurs within the wheelcylinder can be accomplished by diverting some of the

fluid into a small reservoir.

The ABS must re-pump this reservoir's fluid back into themain fluid reservoir.


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Anti Brake System