1. Anti-lock braking systems (ABS) prevent wheels from locking up during braking, allowing the driver to steer and maintain control. 2. The main components of ABS are speed sensors to detect wheel slippage, valves to regulate brake fluid pressure, a pump to restore pressure, and a controller to process sensor data and operate the other components. 3. When ABS detects impending wheel lock, it rapidly pumps the brakes on and off up to 15 times per second to maintain traction between the tires and road surface.

1. GUJARAT TECHNOLOGICAL
UNIVERSITY
L.D. COLLEGE OF ENGINEERING,
AHMEDABAD.

2. M. E. (I. C. E. & AUTO.)
SEMESTER – 3rd
YEAR 2014 - 15.
AUTOMOTIVE AERODYNAMICS
& SAFETY (2731104)

3. ANTI-LOCK BRAKE
SYSTEM (ABS)
Prepared By: G. A. KAPADIA (140280711009)
A. H. SHUKLA (140280711016)

4. ANTI-LOCK BRAKE SYSTEM:
Introduction:
 Wheel lockup during braking causes skidding which in
turn cause a loss of traction and vehicle control
 This reduces the steering ability to change direction. So
the car slides out of control
 With ABS system, the driver can brake hard, take the
evasive action and still be in control of the vehicle in
any road condition at any speed and under any load.

5. ANTI-LOCK BRAKE SYSTEM:
 Anti-lock braking system (ABS) is an automobile safety system
that allows the wheels on a motor vehicle to maintain tractive
contact with the road surface according to driver inputs while
braking, preventing the wheels from locking up (ceasing rotation)
and avoiding uncontrolled skidding.
 ABS generally offers improved vehicle control and decreases
stopping distances on dry and slippery surfaces; however, on
loose gravel or snow-covered surfaces, ABS can significantly
increase braking distance, although still improving vehicle
control.

6. CONCEPT OF ABS
 A skidding wheel (where the tire contact patch is
sliding relative to the road) has less traction than a non-
skidding wheel
 By keeping the wheels from skidding while you slow
down, anti-lock brakes benefit you in two ways:
 Vehicle will stop faster, and it will be able to steer while
you stop.

7. COMPARISON

8. COMPONENTS OF ABS
There are four main components of ABS: speed sensors, valves, a
pump, and a controller.
1. Speed sensors:
A speed sensor is used to determine the acceleration or
deceleration of the wheel. 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. The fluctuations of this
magnetic field generate a voltage in the sensor. Since the voltage
induced in the sensor is a result of the rotating wheel, this 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 readings to the controller.

9. 2. 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 right through to the brake.
 In position two, the valve blocks the line, isolating that
brake from the master cylinder. This prevents the pressure
from rising further should the driver push the brake pedal
harder.

10. Continue…
 In position three, the valve releases some of the
pressure from the brake.
 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. An inoperable valve will prevent the
system from modulating the valves and controlling
pressure supplied to the brakes.

11. 3. Pump
 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 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
system. The controller will modulate the pumps status in
order to provide the desired amount of pressure and
reduce slipping.

12. 4. 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.

13. ABS TYPES
1. Four-channel, four-sensor ABS
2. Three-channel, four-sensor ABS
3. Three-channel, three-sensor ABS
4. Two-channel, four sensor ABS
5. One-channel, one-sensor ABS

14. WORKING PRINCIPLE OF ABS:

15. WORKING PRINCIPLE OF ABS:

16. ADVANTAGES
 It allows the driver to 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 and
modulates the pulses thus permitting the wheel to
continue turning under maximum braking pressure.

17. DISADVANTAGES
 It is very costly
 Maintenance cost of a car equipped with ABS is
more.

18. REFERENCE:
 http://en.wikipedia.org/wiki/Anti-
lock_braking_system
 http://www.engin.umich.edu/group/ctm/index.html
 How Stuff Works from the article “How Anti-Lock
Brakes Work” http://www.howstuffworks.com/