- The document discusses anti-lock braking systems (ABS) which allow wheels to maintain traction with the road surface under heavy braking to prevent skidding and allow steering control. ABS monitors wheel speed and regulates brake pressure to keep wheels rotating just before the point of lockup. - The key components of ABS are wheel speed sensors, hydraulic valves, an electronic control unit, and a hydraulic control unit. The ECU receives sensor signals, compares wheel speeds, and controls the valves to rapidly modulate brake pressure as needed. - ABS allows shorter braking distances, maintains vehicle stability and steering ability during hard braking, and is useful in wet or icy conditions where standard braking could

1. Anti-Lock Braking System
[ABS]
Presented By
VIKASH KUMAR(B160089ME)
Student of B. Tech, 4th Year, 8th Semester
Mechanical Engineering of 2016-2020 batch
National Institute of Technology Sikkim
Under the Guidance of
MR. SHITENDU SOME
Assistant Professor
Department of Mechanical Engineering
National Institute of Technology Sikkim
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2. Content
 Introduction to Seminar
 Braking System in Automobile
 Principle of Anti Lock Braking System
 Objective of ABS
 Components
 Operation of ABS
 Uses of ABS
 Types of ABS
 Advantage and Disadvantage
 References
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3. Introduction to Seminar
About ABS
• 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 and avoiding uncontrolled
skidding.
• ABS allows the driver to maintain steering control while braking
and shorten braking distances on slippery surfaces like wet or icy
surfaces. But it increases the stopping distances in simple
surfaces.
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4. • ABS is recognized as an important contribution to road safety as it is
designed to keep a vehicle steerable and stable during heavy braking
moments by preventing wheel lock
• It is a hard-real time system. It handles all events even in worst case
in given time constraint.
• Anti-lock braking systems were first developed for aircraft in 1929
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5. Schematic of simple Braking System
Fig 1. Braking System
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6. Braking System in Automobile
• In an automobile System, the brakes are actuated by
hydraulic pressure.
• In simple breaking system, your applied force by depressing
the break pedal simply transmit to the wheel(break) through
incompressible fluid.
• But a simple force applied by human seems to be difficult to
stop a huge running vehicle.
• To multiply the applied force, a hydraulic system is used.
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7. • Under braking, if one or more of a vehicle’s wheels lock (begins to
skid) then this has number of consequences: a) braking distance
increases, b) steering control is lost, and c) tire wear will be
abnormal.
• ABS systems are designed around system hydraulics, sensors and
control electronics. These systems are dependent on each other
and the different system components are interchangeable with
minor changes in the controller software.
Principle of Anti Lock Braking System
Figure-2, Block representation of an
ABS
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8. Objective of ABS
The major role played by ABS in automobile are:
• To reduce stopping distance: The wheel slip is regulated so that the
road adhesion coefficient is maximized. By keeping all of the wheels
of a vehicle near the maximum friction coefficient, an antilock system
can attain maximum fictional force
• Stability: The basic purpose of a conventional ABS system is thus to
prevent any wheel from locking and to keep the longitudinal slip in an
operational range by cycling the braking pressure.
• Steerability: With ABS car remains steerable even during emergency
braking, and thus the obstacle can be safely avoided.
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9. Components of ABS
ABS has major four main components:
• Speed sensor: -This sensor monitors the speed of each wheel and
determines the necessary acceleration and deceleration of the
wheels. It consists of an exciter and a wire coil/magnet assembly,
which generates the pulses of electricity as the teeth of the exciter
pass in front of it.
Figure-3: ABS Speed Sensors
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10. .
• Valves: -The valves regulate the air pressure to the brakes during
the ABS action. There is a valve in the brake line of each brake
that is controlled by ABS. 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
Figure-4 Partially disassembled four-channel
hydraulic control unit containing motor, pump
and valves
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11. • Electronic control unit (ECU): -ECU that receives
amplifies and filters the sensor signals for calculating the
wheel rotational speed and acceleration. It receives the
signals from the sensors in the circuit and control the
brake pressure.
Figure-5: Electronic Control Module
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12. • Hydraulic control unit: -It receives the signals from the ECU
to apply or release the brakes under the anti-lock
conditions.
• Wheel sensor unit :Speed sensors are comprised of a
magnet wrapped in a coil and a toothed sensor ring. An
electrical field given off by the contact between the magnet
and the toothed ring creates a AC voltage.
.
Figure-6, Hydraulic Control Unit
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13. • First of all wheel speed sensor detects speed based on speed
of rotating toothed wheel
• Increase in no. of pulses generated if wheel speed increases
• Decrease in no. of pulses generated if wheel speed
decreases
• No change in no. of pulses generated if wheel speed remains
same
• No. of pulses generated is sent to ECU
• ECU compares the inputs coming from different channels
• ECU generates suitable control signals
Operation of ABS 13

14. Uses of ABS
• . The controller monitors the speed sensor at all the times. It is
looking for deceleration in the wheel that are out of the ordinary.
Right before wheel locks up, it’ll accelerate a rapid deceleration. If.
• The ABS controller knows that such a rapid deceleration is impossible,
so, it reduces the pressure to that brake until it sees and acceleration,
then it increases the pressure until it sees the deceleration again. left
unchecked, the wheel would stop much more quickly than any car
would.
• When the ABS system is in the operation the driver will feel a pushing
in the brake pedal; this comes from the rapid opening and closing of
the valves
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15. Types of ABS
• Four Channel, Four Sensor ABS
• Three Channel, Three Sensor ABS
• One Channel, One Sensor ABS
Figure-8, Types of ABS (Block Diagram)
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16. Advantage
• It allows the driver to maintain the 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.
• ABSs are compatible with industry standard hand-held and computer-
based diagnostic tools
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17. Disadvantage
• It is very costly.
• Maintenance cost of car equipped with ABS is more.
• Since the primary objective of ABS is to give steer ability
and hence the stopping distance may not necessarily
decrease every time.
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18. References
• Antilock Braking System Modeling and Development, Indian Institute of Technology
Hyderabad.
• Tianku Fu, “Modeling and performance analysis of ABS system with non-linear control”,
2000.
• Tobias Eriksson, “Co-simulation of full vehicle model in Adams and anti-lock brake system
model in Simulink”, 2014.
• An Investigation Into New ANS Control Strategies, 2016-04-05, Journal Article 2016-
01-1639,Jonathan Loyola,Francis Assadian.
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