The document summarizes an intelligent braking system called an Anti-lock Braking System (ABS). It discusses what ABS is, the motivation for its development to prevent locked wheels and maintain stability, provides a history of ABS from its invention in 1936 to widespread adoption. It then outlines the key components of ABS including wheel speed sensors, electronic control unit, hydraulic modulator unit, and how ABS works by rapidly pulsing the brakes to prevent locking. Design challenges and limitations that ABS does not allow for faster driving, braking later or cornering are also covered.

1. Major Assignment on
intelligent braking system
Submitted by Submitted to
Sagar Bhardwaj Mr. Amardeep singh
K10692 (asst. prof. ME dept)

3. Presentation Outline
• What is an Anti-Lock Braking System (ABS)?
• Motivation for ABS Development
• History of ABS
• Overview
• Principles for ABS Operation
• ABS Components Overview
• ABS Components
• How does ABS work?
• Design Challenges
• Limitations
• Summary

4. 1. What is ABS?
• “An anti-lock brake system is a feedback
control system that modulates brake pressure
in response to measured wheel deceleration,
preventing the controlled wheels from
becoming fully locked.”

5. 2. Motivation for ABS
• Under hard braking, an ideal braking system should:
 provide the shortest stopping distances on all surfaces
 maintain vehicle stability and steerability
Anti-lock braking systems were developed to
best meet these needs.

6. 3. History of ABS
• 1936: German company Bosch is awarded a patent for
an “Apparatus for preventing lock-braking of wheels
in a motor vehicle”.
• 1936-: Bosch and Mercedes-Benz partner - R&D into ABS.
• 1972: WABCO partners with Mercedes-Benz developing first ABS
for trucks.
• 1978: First production-line installation of ABS into Mercedes and
BMW vehicles.
• 1981: 100,000 Bosch ABS installed.
• 1985: First ABS installed on US vehicles.

7. • 1986: 1M Bosch ABS installed.
• 1987: Traction control - in conjunction with ABS - used
on passenger
vehicles.
• 1989: ABS hydraulic unit combined with standard hydraulic
brake unit
• 1992: 10M Bosch ABS installed.
• 1995: Electronic Stability - in conjunction with ABS and
TCS - for passenger cars.
• 1999: 50M Bosch ABS installed.
• 2000: 6 of 10 new cars on the road are ABS equipped.
• 2003: 100M Bosch ABS installed.

8. 4. Overview
• Anti-Lock Braking Systems (ABS) are designed to maintain
driver control and stability of the car during emergency
braking. Locked wheels will slow a car down but will not
provide steering ability. ABS allows maximum braking to be
applied while retaining the ability to
'steer out of trouble‘ . The operation of ABS can slightly
reduce stopping distance in some cases like on wet road
surfaces, but it can increase the stopping distance in others,
as may be the case in deep snow or gravel.

9. • An ABS system monitors four wheel speed sensors to
evaluate wheel slippage. Slip can be determined by
calculating the ratio of wheel speed to vehicle speed, which is
continuously calculated from the four individual wheel
speeds. During a braking event, the function of the control
system is to maintain maximum possible wheel grip on the
road - without the wheel locking - by adjusting the hydraulic
fluid pressure to each brake by way of electronically
controlled solenoid valves.

10. 5. Principles for ABS Operation
 Design Goals:
• attain minimum stopping distance
• maintain stability and steerability
 Design Solution:
Develop a system that rapidly modulates the
braking force under hard braking conditions to:
• maintain the ideal tire slip percentage to
maximize braking force (≈ 15%), recalling
that Fbrake = µBN
• permit the vehicle to be steered with
stability maintained by preventing skidding

11. 6. ABS Components Overview
Typical ABS Components:
 Wheel Speed Sensors (up to 4)
 Electronic Control Unit (ECU)
 Brake Master Cylinder, Hydraulic
Modulator Unit with Pump and Valves
 Vehicle’s Physical Brakes

12. ABS Components
• Wheel Speed Sensor (WSS)
• Hydraulic Modulator Unit

13. a) Wheel Speed Sensor (WSS)
Teeth on the sensor ring
rotate past the magnetic
sensor, causing a reversal
of the magnetic field
polarity, resulting in a signal
with frequency related to
the angular velocity of the
axle.

14. Electronic Control Unit
The signal from the WSS is
proportional to angular velocity. By
differentiating this signal,
acceleration of each wheel is known.
If a wheel is decelerating too quickly
the brake pressure is modulated.
A fifth input to the ECU is from a
brake pedal switch. This signal can
shift program execution from a
standby to an active state

15. b) Hydraulic Modulator Unit
The hydraulic modulator unit
contains the ABS pump as
well as solenoid valves for
each brake line.
The fifth line - far right - is
from the brake master
cylinder, which is connected
to the brake pedal.

16. Valves and Brakes
The valves modulate the
brake pressure up to 20 times
per second, effectively
realizing the ideal tire slip
percentage.
ABS ‘pumps’ the brakes much
faster than any driver could.

17. 7. How does ABS work?
Basically, there are sensors at each of the four wheels (or in the case of the
less sophisticated three-channel system, one on each of the fronts and only one
for the pair of rears). 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 car's computer, which then releases some of the brake line pressure that
you've applied - allowing the wheel to turn again. Then, just as fast as it released
the pressure, the computer allows the pressure to be applied again - which stops
the rotation of the wheel again. Then it releases it again. And so on. With most
ABS, this releasing and re-application - or pulsing - of the brake pressure
happens 20 or more times per second.
Practically speaking, this keeps the wheel just at the limit - the threshold - before
locking up and skidding. ABS prevents you from ever locking up the brakes and
skidding - no matter how hard you apply the brakes. Obviously, this is going to
mean much more steering control.
With ABS, all you have to do in an emergency is quickly squeeze the brake
pedal as hard as you can and hold it there. And when I say hard, I mean HARD.
Let the system do the finesse work for you. This may not be as easy as it sounds.
After years of being told (and practising) not to press too hard on the brake pedal,
this may not feel very natural.

18. 8. Design Challenges
Because of the safety-related nature of the ABS application,
special emphasis is placed on functions designed to detect
system faults and ensure that a fail-safe state occurs during
faults. These functions may be implemented with techniques
such as dual processors and specialized self test and
watchdog modules.
ABS systems typically include eight electric solenoid valves
and other electrical loads, such as relays and pump motors,
that require considerable drive currents. Electronic drive
circuitry is often required to sense any failure of these
components during operation.

19. 9. Differences between ABS and Rear
Anti-lock Brakes.
• Finally, there is a great difference between ABS and Rear
Anti-lock Brakes. ABS is on all four wheels. Rear Anti-lock
Brakes, as the name suggests, are only on the rear wheels.
This system is often used on pick-up trucks and vans, and is a
less-expensive compromise. It is used because the weight
load on the rear of a truck or van can vary so much. The
brakes needed to handle a heavily loaded vehicle are too
effective for when it is lightly loaded. Therefore, the rear
brakes are much more susceptible to locking-up.

20. 10. Limitations
Three points should be obvious, but don't appear to
when looking at the type of crashes some drivers
have with ABS-equipped vehicles. Contrary to
popular belief, ABS :-
• does not allow you to drive faster;
• does not allow you to brake later; and
• does not allow you to corner faster.

21. 11. Summary
• An ABS typically consists of:
– Up to 4 wheel speed sensors
– An ABS ECU
– A Brake Master Cylinder, with accompanying Hydraulic
Modulator Unit and Solenoid Valves
– The vehicle’s physical brakes
• An ABS is designed to modulate braking pressure to attain the peak
coefficient of kinetic friction between the tire and the road, and to
avoid total wheel lockup.
• An ABS, under hard braking conditions, is designed to reduce
stopping distances under most conditions, while maintaining
vehicle stability and steerability.

22. •You have to understand that ABS does not raise the
traction limits of your vehicle. It only helps you stay within
the limits. Period. So, don't get caught up in believing that
ABS will allow you to drive any faster, brake later or go
around a corner any faster - or allow you to safely follow
any closer.

23. THANK YOU