The document discusses anti-lock braking systems (ABS). It provides an overview of ABS, including its history, components, principles of operation, types, and advancements like electronic stability control. ABS prevents wheel locking under heavy braking, allowing the driver to steer and maintain vehicle control. It modulates brake pressure to keep wheels rotating at an optimal slip rate for maximum braking force. ABS improves safety by reducing skidding and keeping vehicles stable during emergency stops on slippery surfaces.

1. Shaheem
TM Reg. No.
90012064
DOI ,
Anti-lockBrakingS
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2. Overvie
w
 Introduction
 What is ABS
 Timeline of ABS
 Motivation for development
 Simple hydraulic braking
system
 Principles of ABS
 Components
 Working
 Types
 Advancements
 Advantages & Disadvantages
 summary

3. Introductio
n
 Conventional braking system - Wheel lockup
 Reduces steering ability - vehicle slides out of control
 Anti-lock Braking system (ABS) – Driver can break hard- No
locking of
wheels

4. What is ABS
?
 Anti-lock braking system (ABS) - automobile
safety
system
 Prevent wheel locking
 Skidding wheel - less traction than a Non-skidding
wheel
 Anti-lock brakes benefit
Can stop faster
Steer while you
stop
Preventing skidding
Maintain traction

5. Motivation for ABS
development
Under hard braking – Ideal system
should
 Provide the shortest stopping
distances
on all surfaces
Maintain vehicle stability and steer
ability.

6. Compariso
n

7. Simple Hydraulic Braking
system
Consists of
 Master cylinder
 Four wheel
cylinders

8. Simple Hydraulic Braking
system
Brake
s
Applie
d
Pistons
pushes
fluid
from
Master
cylinde
r
Fluid
pushes
pistons
of
wheel
cylinder
s
Brake
shoes
pushe
d out
Wheel
s get
locked
Vehicl
e
stops

9. Principles of
ABS
 When brakes applied- vehicle speed comes down
 Decrease in vehicle speed not always proportional to decrease in wheel
speed
 Non-correspondence - Slip
 Magnitude measured as Slip ratio
Slip ratio = [(Vehicle speed – Wheel speed)/Vehicle speed ]× 100%
When
Slip ratio = 0% : Vehicle speed corresponds exactly to wheel speed
Slip ratio = 100% : Wheels locked - vehicle moves

10.  Best braking action
between
10-20%.
 If vehicle speed and
wheel speed is the
same wheel slippage is
0%
 A lock-up wheel will
have a wheel slippage
of 100%
(A) Slip ratio
(B)Coefficient of friction
between tire and road
surface
(1) Icy road
(2) Asphalt-paved
road
(3)Control range by

11. Pressure Modulation in
ABS
 Release and reapply of the brake pedal – avoid locking of wheels -
avoid the
skidding
 Antilock braking system does the same
 Brakes applied - pressure is quickly applied & released at the wheels -
pressure modulation
 Pressure modulation prevent the wheel locking
 ABS modulate the pressure 15 times per seconds
 ABS precisely controls the slip rate of wheels - ensure maximum grip force
from the tyre - ensures maneuverability and stability

12. ABS Components
Overview
1.Hydraulic Unit
2.Electronic Brake Control Module
[EBCM] 3.Four wheel speed sensors
4.Interconnecting wiring
5.ABS indicator

13. ABS
components
ABS systems
are
 Integrated
 Non-
integrated

14. ABS
components
ABS has four Primary
Components
 ABS Controller
 ABS Speed Sensors
 ABS Modulator/Valves
 ABS Pumps

15. Working of
ABS
Under normal braking
 Brakes applied
 No current flow from ECU to hydraulic unit
 Solenoid valves not energized – brake master cylinder
pressure
reaches wheels Vehicles stops
 ABS not involved - Still ECU monitors each wheel for
lock- up

16. Working of
ABS
When wheel lock-up sensed
 Wheel sensors senses a wheel lock-up
 ECU sends a current to hydraulic unit
 The solenoid valve gets energised
 Valve isolates the brake circuit from master cylinder
 Stops the braking pressure at wheel rising – kept it
constant

17. Working of
ABS
Still wheel deceleration is rapid
 ECU sends larger current to hydraulic unit
 Armature of Hydraulic unit moves faster
 Opens a passage : Brake circuit – Master
cylinder
 Pressure in brake caliper reduced

18. Working of
ABS
When wheel is accelerated again
 ECU stops current to Hydraulic unit
 De-energises the solenoid valve
 Pressure is build up
 The cycle repeats several times in a
second
 Vehicle stops safely

20. Working of solenoid valve in
ABS
It has 3 modes
 Increase
pressure
 Hold pressure
 Decrease
pressure

21. Solenoid 1
Pressure
increase
Solenoid 2
Pressure decrease/Vent
solenoid
Brake line under pressure
Brake fluid line not under
Increase
pressure

22. Solenoid 1
Pressure
increase
Solenoid 2
Pressure
decrease/Vent
Pressure
hold

23. Solenoid 1
Pressure
increase
Solenoid 2
Pressure
decrease/Vent
Pressure
decrease

24. Types of
ABS
Three types
 Four channel – Four sensor
ABS
 Three channel – Three sensor
ABS
 One channel – One sensor
ABS

26. Advancemen
ts
 Automatic Stability Control / Electronic Stability
Control
(Program) - ESP
 Automatic Traction Control - ATC

27. Automatic Stability Control / Electronic Stability Program -
ESP
Component
s
Yaw rate sensor
ESP hydraulic control
unit
Steering angle sensor
G sensor
Wheel speed
sensors
ECU

28. Operatio
n
Under normal driving
 ESC works in background- monitors steering & vehicle
direction
 Determines intended direction – steering angle sensor
 Determines vehicle’s actual direction- yaw sensor- wheel speed
sensors
 Compares the obtained data

29. Operatio
n
When detects a loss of steering control
 Detects – Understeer or Oversteer
 ESC estimates direction of speed
 Applies brakes to individual wheels asymmetrically
 Create torque about vehicle’s vertical axis- oppose skid
 Brings vehicle back to control
 Additional operation – reduces engine power, operate
transmission

30. Overstee
r
Understee
r

31. Automatic Traction Control -
ATC
 Apply brakes when drive wheel attempts to spin and lose
traction
 A secondary function of ESP
 Activated when throttle input & engine torque is mismatched to
road
surface conditions

32. Automatic Traction Control -
ATC
ATC intervention consists of the following
 Brake force applied to one or more wheels
 Reduction or suppression of spark sequence to one or more
cylinders
 Reduction of fuel supply to one or more cylinders
 Closing the throttle

33. Components of traction
control
 The main hardware for traction control and ABS are
same
 Wheel sensors
 ECU
 ATC valve

34. Advantages of
ABS
 Reduce the stopping distance.
 Steer while the brakes are firmly applied.
 Maintain directional stability and control over steering during
braking.
 Safe and effective.
 Automatically changes the brake fluid pressure at each wheel to
maintain
optimum brake performance.
 ABS absorbs the unwanted turbulence shock waves.

35. Disadvantages of
ABS
 Increased braking distances under some limited
circumstances
 cost
 Maintenance cost of a car equipped with ABS is
more
 System damage

36. Summar
y
The antilock braking system controls braking force by controlling the
hydraulic pressure of the braking system, so that the wheels do not
lock during braking.
The antilock braking system prevents wheels locking or skidding, no
matter how hard brakes are applied, or how slippery the road surface.
Steering stays under control and stopping distances are generally
reduced.