1.1 Types
of Braking System
Brakes can be broadly classified into
following types;
Ø
Mechanical
brakes
·
Disc
brake
·
Drum
brake
Ø
Hydraulic
Brakes
Ø
Power
Brakes
·
Air
brake
·
Air
Hydraulic brake
·
Vacuum
brakes
·
Electro-mechanical
brake or electric brake
·
1. MECHANICAL
BRAKES
a) Disc
Brake
It is a type of
brake that uses calipers to squeeze pair of pads against disc or rotor which is
attached to the wheel by creating frictional force between them and retards the
motion of rotating shaft connected to it. A disc brake work on the principle of
transmission of fluid pressure. This law states that,” the pressure exerted
anywhere in a confined incompressible fluid is transmitted in all directions
throughout the fluid such that the pressure ratio remains same.”
b) Drum
Brakes
A drum brake is
that brake which uses friction caused by set of shoes or pads that press
outward against a rotating cylinder part called as brake drum. It is commonly used in vehicles where high
amount of brake force is required like heavy duty vehicles, medium vehicles,
etc.
c) Hydraulic
Brakes
A hydraulic braking
system is piston cylinder arrangement consisting of incompressible fluid
typically glycol ethers or diethylene glycol which multiplies force
significantly. It works on Pascal’s law and transfers hydraulic pressure.
d) Power
Brakes
Ø
Air
brakes
Ø
Air
hydraulic brakes
Ø
Vacuum
brakes
Ø
Electro-mechanical
brakes
Brakes
A brake is a device
which inhibits motion. Its opposite component is a clutch. Most commonly brakes
use friction to convert kinetic energy into heat, though other methods of
energy conversion may be employed. The principle of braking in road
vehicles involves the conversion of kinetic energy into thermal energy (heat).
When stepping on the brakes, the driver commands a stopping force several times
as powerful as the force that puts the car in motion and dissipates the
associated kinetic energy as heat. Brakes must be able to arrest the speed of a
vehicle in a short periods of time regardless how fast the speed is. As a
result, the brakes are required to have the ability to generating high torque
and absorbing energy at extremely high rates for short periods of time. Brakes
may be applied for a prolonged periods of time in some applications such as a
heavy vehicle descending a long gradient at high speed. Brakes have to have the
mechanism to keep the heat absorption capability for prolonged periods of time.
Electromagnetic
Brakes
Electromagnetic brakes (also called
electro-mechanical brakes or EM brakes) slow or stop motion using
electromagnetic force to apply mechanical resistance (friction). Since becoming
popular in the mid-20th century especially in trains and trams, the variety of
applications and brake designs has increased dramatically, but the basic
operation remains the same. Electromagnetic brakes have been used as
supplementary retardation equipment in addition to the regular friction brakes
on heavy vehicles. Electromagnetic brakes are the brakes working
on the electric power & magnetic power. They works on the principle of
electromagnetism. The working principle of this system is that when the
magnetic flux passes through and perpendicular to the rotating wheel the eddy
current flows opposite to the rotating wheel/rotor direction. This eddy current
trying to stop the rotating wheel or rotor. This results in the rotating wheel
or rotor comes to rest/ neutral.
Electronic Brake
Force Distribution
Electronic brake force
distribution (EBD or EBFD) or electronic brake force limitation (EBL) is an
automobile brake technology that automatically varies the amount of force
applied to each of a vehicle's wheels, based on road conditions, speed,
loading, etc. EBD is an
active vehicle safety feature designed to make braking as efficient as
possible. EBD prevents wheel from locking under
various driving condition by regulating brake pressure. This is because the car
will have less braking distance or maximum deceleration when both wheels retard
at same rate, this is where EBD kicks in by applying right pressure to each
wheel. EBFD reduces these dangers by automatically balancing the brake
force applied to each wheel according to the overall weight distribution of the
vehicle.
Electromagnetic brakes when coupled with electronic brake force
distribution(EBD) help us in swift driving as it satisfy all the energy
requirement of braking without the use of friction, reduce slip ratio on the
tyres. EBD helps to distribute the brake force equally on both front and rear
wheel which results in effective braking that reduce the risk of fishtailing,
spinning, over steering, and understeering. A special function of antilock
braking systems (ABS), EBFD makes the amount of brake force applied to a wheel
proportional to that wheel’s load at the time.
The principle of
braking in road vehicles involves the conversion of kinetic energy into thermal
energy (heat). When stepping on the brakes, the driver commands a stopping
force several times as powerful as the force that puts the car in motion and
dissipates the associated kinetic energy as heat. Brakes must be able to arrest
the speed of a vehicle in a short periods of time regardless how fast the speed
is. As a result, the brakes are required to have the ability to generating high
torque and absorbing energy at extremely high rates for short periods of time.
Brakes may be applied for a prolonged periods of time in some applications such
as a heavy vehicle descending a long gradient at high speed. Brakes have to
have the mechanism to keep the heat
absorption capability
for prolonged periods of time. Electromagnetic Braking system works on the
principle of electromagnetism.
EBD distributes the necessary amount of brake force required for
effective braking. According to the weight distribution over the vehicle except
dead load, it provides necessary brake force to each brake. Under no load condition, small brake force is
provided to rear wheel and when loads i.e passengers and their luggage is
added, then for vehicle to stop at safest distance in emergency braking, it is
required to provide rear wheel greater brake force which is provided by EBD.
History
It is found that
electromagnetic brakes can develop a negative power which represents nearly
twice the maximum power output of a typical engine, and at least three times
the braking power of an exhaust brake (Reverdin 1994). These performance of
electromagnetic brakes make them much more competitive candidate for
alternative retardation equipment’s compared with other retarders. By using by
using the electromagnetic brakes are supplementary retardation equipment, the
friction brakes can be used less frequently, and therefore practically never
reach high temperatures. The brake linings would last considerably longer
before requiring maintenance and the potentially brake fade problem could be
avoided. In research conducted by a truck manufacturer, it was proved that the
electromagnetic brake assumed 80% of the duty which would otherwise have been
demanded of the regular service brake (Reverdin 1974). The installation of an
electromagnetic brake is not very difficult if there is enough space between
the gearbox and the rear axle. If did not need a subsidiary cooling system. Electronic
brake force distribution (EBFD) is a braking system that monitors factors like
vehicle weight and road condition and adjusts the vehicle's braking force
accordingly. Some vehicle manufacturers provide EBFD as a standard feature. EBD
has been used in some vehicles with anti-locking braking system(ABS) but some
test have been conducted with EM brakes and it has not been installed for
commercial use.
2.
Significance/Scope
Ø EM
brakes are already in use under some railway system.
Ø EM
brakes are equally applicable to heavy and light vehicles.
Ø EBD
can deduce the car from the slip ratio of the wheels and compensate accordingly
in icy or watery roads.
Ø When
a truck with heavy loads apply brakes EBD becomes aware of it through its
effect on the slip ratio of the tires and distributes equal amount of brake
force to all wheels.
Ø Heavy
braking will be more comfortable: since braking is more effective with EBFD,
your vehicle will stop faster.
3. Limitations
Ø The
installation of an electromagnetic brake is very difficult if there is not
enough space between the gearbox and the rear axle.
Ø Due to residual magnetism present in
electromagnets, the brake shoe takes time to come back to its original
position.
Ø EBFD
cannot warn of impending collisions or of bad road conditions, so it is up to
us to assess road conditions and notice any potential hazards.
YV Nitesh
10th Jan 2019
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