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By
PRATEEK M NAIK
1RE08ME036
MECHANICAL DEPARTMENT
REVA ITM
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INTRODUCTION
Vehicle skid can be defined as the loss of traction between a
vehicles tires and the road surface due to the forces acting on the
vehicle. This skid of car causes loss of control and resulting in
OVERSTEER and UNDERSTEER problem.
To reduce OVERSTEER and UNDERSTEER effect on a
motor vehicle , modern technologies such as ANTILOCK BRAKING
SYSTEM , ELECTRONIC STABILITY PROGRAM , TRACTION CONTROL
SYSTEM & ELECTRONIC BRAKE FORCE DISTRIBUTION systems are
utilized . The thesis displays the use of such system on vehicle
stability and remedial measures to be taken.
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OVERSTEER
A car that oversteer turns very sharply, moving the rear of the car to slide outside
of a corner while its front points towards the inside.
Oversteer occurs when a cars front tires have more traction than the rear tyres,particularly with rear wheel drive cars.
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UNDERSTEER
When a car understeer, the front end of the car slides to the outside of a turn
instead of taking the turn.
Understeer occurs when the rear tires have more traction than the front tires, whichoften happens with frontwheel drive cars.
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VEHICLE SKID
CONTROL
The Vehicle Skid Control (VSC) is made possible by the combination of different
electronic and mechanical components.
Main objective is to , sense the onset of traction loss and keep the driver on track.
These skid control systems are often integrated with the engine management
system to cut power in even more tricky situations.
Here a complex system of sensors and microprocessors that continually monitor
the vehicle for any signs of instability.
Once detected (usually in the form of a slide or skid), the system automatically
applies selective braking to specific wheels thereby stabilizing the vehicle.
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Yaw rate sensor
G-sensor
Steering angle sensor
Electronic throttle control
Slip indicator
Computer
COMPONENTS OF
Vsc
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ANTILOCK BRAKING
SYSTEM
An anti-lock braking system (ABS, from German: Antiblockiersystem) is a safety
system that allows the wheels 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 (that is, ceasing rotation)
and therefore avoiding skidding.
An ABS generally offers improved vehicle control and decreases stopping
distances on dry and slippery surfaces for many drivers; however, on loose
surfaces like gravel or snow-covered pavement, an ABS can significantly increase
braking distance, although still improving vehicle control
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COMPONENTS OF ABS
There are four main components to an ABS:
SPEED SENSOR
ABS VALVES
ABS PUMP
ABS ACTUATORS
ABS CHANNEL
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WORKING OF ABS
The ECU constantly monitors the rotational speed of each wheel; if it detects a
wheel rotating significantly slower than the others, a condition indicative of
impending wheel lock, it actuates the valves to reduce hydraulic pressure to the
brake at the affected wheel, thus reducing the braking force on that wheel; the
wheel then turns faster.
Conversely, if the ECU detects a wheel turning significantly faster than the others,
brake hydraulic pressure to the wheel is increased so the braking force is reapplied,
slowing down the wheel. This process is repeated continuously and can be
detected by the driver via brake pedal pulsation.
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TYPES OF ABS
FOUR CHANNEL , FOUR SENSOR ABS
THREE CHANNEL , FOUR SENSOR ABS
THREE CHANNEL , THREE SENSOR ABS
ONE CHANNEL , ONE SENSOR ABS
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ELECTRONIC STABILITY
PROGRAM
ESP systems are an evolution of the ABS concept. Here, a minimum of two
additional sensors are added to help the system work: these are a steering wheel
angle sensor, and a gyroscopic sensor.
When the gyroscopic sensor detects that the direction taken by the car does not
coincide with what the steering wheel sensor reports, the ESC software will brake
the necessary individual wheel(s) , so that the vehicle goes the way the driver
intends.
The steering wheel sensor also helps in the operation of Cornering Brake Control
(CBC), since this will tell the ABS that wheels on the inside of the curve should
brake more than wheels on the outside, and by how much.
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A traction control system (TCS), also known as anti-slip regulation (ASR), is typically
(but not necessarily) a secondary function of the anti-lock braking system (ABS) on
production motor vehicles, designed to prevent loss of traction of driven road
wheels.
When invoked it therefore enhances driver control as throttle input applied is mis-
matched to road surface conditions (due to varying factors) being unable to
manage applied torque.
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OVERSTEER & UNDERSTEER CAUSED BY TRACTION LOSS
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When the traction control computer detects one or more driven wheels spinningsignificantly faster than another, it invokes ABS ecu to apply brake friction to wheels
spinning with lessened traction.
Braking action on slipping wheel(s) will cause power transfer to wheel axle(s) with
traction due to the mechanical action within a differential.
All-wheel drive AWD vehicles often have an electronically controlled coupling
system in the transfer case or transaxle engaged (active part-time AWD), or locked-
up tighter (in a true full-time set up driving all wheels with some power all the
time) to supply non-slipping wheels with (more) torque.
This often occurs in conjunction with the powertrain computer reducing available
engine torque by electronically limiting throttle application and/or fuel delivery,
retarding ignition spark, completely shutting down engine cylinders, and a number
of other methods, depending on the vehicle and how much technology is used to
control the engine and transmission.
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Electronic brake force distribution (EBD or EBFD), Electronic brake force limitation
(EBL) is an automobile brake technology that automatically varies the amount of
force applied to each of a vehicle's brakes, based on road conditions, speed,
loading, etc.
Always coupled with anti-lock braking systems, EBD can apply more or less braking
pressure to each wheel in order to maximize stopping power while maintaining
vehicular control.
The front end carries the most weight and EBD distributes less braking pressure to
the rear brakes so the rear brakes do not lock up and cause a skid.
In some systems, EBD distributes more braking pressure at the rear brakes during
initial brake application before the effects of weight transfer become apparent
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EBD may work in conjunction with ABS and Electronic Stability Control ("ESC") tominimize yaw accelerations during turns.
ESC compares the steering wheel angle to vehicle turning rate using a yaw rate
sensor. "Yaw" is the vehicle's rotation around its vertical center of gravity
If the yaw sensor detects more/less yaw than the steering wheel angle shouldcreate, the car is understeering or oversteering and ESC activates one of the front
or rear brakes to rotate the car back onto its intended course
If a car is making a left turn and begins to understeer (the car plows forward to the
outside of the turn) ESC activates the left rear brake, which will help turn the car
left.
The sensors are so sensitive, and the actuation is so quick that the system may
correct direction before the driver reacts. ABS helps prevent wheel lock-up and EBD
helps apply appropriate brake force to make ESC work effectively.
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ADVANTAGEs &
DISADVANTAGEs
ADVANTAGES
Monitors each wheel independently maximizing the performance of the car.
Increases comfort, both physical and psychological.
Improves safety aspects of the car and the driver.
Helps save money long term.
Enhances the ability to dodge a renegade object in its pathways.
DISADVANTAGES
High initial costs.
Overdependence.
Not perfect.
Repairing cost may be high.
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REMEDIAL MEASURES
In each case, the cause can be removed by taking the foot off the accelerator or brake
and depressing the clutch. The reasons are as follows:-
By decelerating, the vehicles speed is lowered, which in turn will start to reduce the
magnitude of the skid.
Relaxation of the pressure on the brake pedal will unlock the wheels and allow the tyres
to regain traction, enabling the vehicle to be steered.
Depressing the clutch pedal has 3 beneficial effects:
(i) The engine will not stall, enabling the vehicle to be moved quickly from the danger
area.
(ii) The link between engine & transmission is broken, there is no drive to any of the
wheels, therefore the vehicle is no longer a front, rear or four wheel drive model.
(iii) A very slippery surface can cause the drive to lock up which in turn causes the wheels to
lock, keeping the vehicle in a skid situation.
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conclusion
Latest generation of stability control systems offer drivers increased protection
for both themselves and the vehicle, they can never overcome poor judgment or
the laws of physics
When we drive, it not only affects our safety but the safety of
everyone around us whether driving or not. With increasing development in the
field of automobiles, it is only imperative that we go for vehicles that have these
technologies installed in them. Vehicle Skid Control would not, in anyway,
eliminate all road accidents; however it would lower the percentage of crashes
thereby lowering the number of fatalities.
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BIBLIOGRAPGHY
www.experiencemad.co.uk
www.trailer-bodybuilders.com
www.graham-sykes.co.uk
www.lexus.com
www.howstuffworks.com
Heitner Joseph,Automobile Mechanics,2nd ed ,East West press, New
Delhi, 2001
Sing Harbans , The Automobile,1st editions Chand, New Delhi,2001
http://www.experiencemad.co.uk/http://www.trailer-bodybuilders.com/http://www.graham-sykes.co.uk/http://www.lexus.com/http://www.howstuffworks.com/http://www.howstuffworks.com/http://www.lexus.com/http://www.graham-sykes.co.uk/http://www.graham-sykes.co.uk/http://www.graham-sykes.co.uk/http://www.trailer-bodybuilders.com/http://www.trailer-bodybuilders.com/http://www.trailer-bodybuilders.com/http://www.experiencemad.co.uk/8/2/2019 1 Re 08 Me 036
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