anti lock breaking system

1. PRESENTED BY:
Srinivasa Raju.O
16881A0342
4th Year
Mechanical
Technical Seminar on:

2. CONTENTS
 What is an ABS
 How abs can replace conventional brake
 principle for ABS
 ABS Components
 Working of ABS
 Working of ABS (video)
 Anti lock brake types
 Advantages & Disadvantages
 Conclusion

3. WHAT IS AN ABS..?
An anti-lock braking system (ABS) is a safety anti-skid braking
system used on aircraft and on land vehicles, such as cars, motor
cycles, trucks and buses
ABS is a system operates by preventing the wheels from locking up
during braking, This enables the driver to have steering control,
preventing sliding and loss of traction thereby
maintaining tractive contact with the road surface.

4. HOW ABS CAN REPLACE CONVENTIONAL BRAKE
• Braking forces are transferred depends on the traction and this in turn
on the brake slip (sliding motion) between tires and road.
• As slip increases, the usable traction also initially increases (stable
range). As greater braking force is applied, the slip continues to increase
and traction is reduced. This ultimately results in the wheels locking
(unstable range).
• An anti-lock braking system (ABS) is a safety anti-skid braking system
prevents the wheels from locking by reducing the braking force. Any
vehicle equipped with ABS remains directionally stable and steerable
even during emergency braking on slippery road surfaces, since the
wheels do not lock (exception: Off-road ABS).

5. Principle of ABS
An anti-lock brake system is a feedback control system that
modulates brake pressure (release and re-apply) in response to
measured wheel deceleration, preventing the controlled wheels
from becoming fully locked thus avoiding uncontrolled skidding.
Wheel speed
Sensor
d/dt
Software
ABS Logic
& Control
ABS ECU
Modulation
Valves
Brake Application
Hydraulic Pressure
Ang. Vel Ang. Acc
Solenoid
Signal
Axil or
Wheel
Rotation

6. COMPONENTS OF ABS
An anti-lock braking system consists of
1) operating brake valve
2) pressure control valve
3) control unit
4) brake cylinder and
5) speed sensor.
Its working is similar to that of hydraulic
breaking system

7.  When the brakes are applied ,fluid is forced from the master cylinder
to the each wheel.
 After the fluid in inserted in each wheel, the wheel starts locking-up.
 ABS consists ECU unit, which monitors the vehicle speed (i.e.., each
tire speed) there by slipping is calculated, during braking if the wheels
are advancing towards lockup, signals are sent to release the brakes.
Once the tire regains the speed, the pressure is increased again, there
by maintaining traction contact.
 During ABS operation, the target slip rate is 10 to 30%
 0% slip means the wheel is freely rotating while
100% slip means the wheel is fully locked
WORKING

8. Working of ABS

9. BRAKE TYPES
ABS has different types of brakes based on number of channels used.
FOUR-CHANNEL
This scheme is employed in most of the modern cars. In this scheme all the
four wheels have there own individual speed sensors and valves. This gives
best result as all the four wheels can be controlled individually which
ensures the maximum braking force.
THREE CHANNEL
Three channel comes with two combination,
1.Three channel with four sensors and
2.Three channel and three sensors.

10. In three channel and four sensor scheme, along with the four sensors on the each
wheel there is a separate valve for each of the front wheels and a common valve for
the rear wheels.
The three channel and three sensor scheme is mostly employed in pickup trucks.
There are individual sensors and valves for both the front wheels with a common
valve and sensor for both of the rear wheel.
TWO CHANNEL
This system works with four sensors and two valves. It uses a speed sensors at each
wheel, with one control valve for both of the front wheels and the other one for the
rear wheels.
ONE CHANNEL
This system is found on pickup trucks which uses rear wheel ABS. It has one valve
and one sensor for both of the rear wheels. This system is not very effective
because as there is a possibility that one of the rear wheel will lock, reducing the
effectiveness of brakes.

11. 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

12. DIS-ADVANTAGES
• Stop Times – Anti-lock brakes are made to provide for surer
braking in slippery conditions. However, some drivers report
that they find the stopping distances for regular conditions are
lengthened by their ABS system ,either because there may be
errors in the system.
• Cost – An ABS can be expensive to maintain (error in sensors
due to dust, out of calibration)
• Noisy

13. CONCLUSION
 Statistics show that approximately 40% of automobile accidents
are due to skidding
 The antilock braking system controls braking force by controlling
the hydraulic pressure of the braking system, which 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
 If there is an ABS failure, the system will revert to normal brake
operation. Normally the ABS warning light will turn on and let the
driver know there is a fault