DESIGN AND FABRICATION COMPUTER CONTROLLED WIRELESS ROPOT WITH
WIRELESS CAMERA
DESIGN AND FABRICATION OF AUTOMATIC ULTRASONIC SENSOR OPERATED
PNEUMATIC BRAKING SYSTEM
DESIGN AND FABRICATION OF AUTOMATIC ULTRASONIC SENSOR OPERATED
PNEUMATIC BRAKING SYSTEM
ANNA UNIVERSITY CHENNI 600 025 BONAFIDE CERTIFICATE Certified
that this project DESIGN AND FABRICATION OFAUTOMATIC ULTRASONIC
SENSOR OPERATED PNEUMATIC BRAKING SYSTEM is the bonafide work of
N.RAJA who carried out the project work under my supervision
SIGNTURE SIGNTURE Mr.S.BENJAMENLAZARUS ME.,(Ph.D) Mr.N.RANJITH .ME
HEAD OF THE DEPARTMENT Assistant professor Associate professor
Department of mechanical enggDepartment of Mechanical Engg The
Kavery Engineering collegeThe kavery Engineering college Submitted
for the University Viva-voce Examination held
on____________________INTERNAL EXAMINER EXTERNAL EXAMINER
CONTENTS
CHAPTER 1SYNOPSIS The brake system on a tractor-trailer is an
"S-Cam Air Brake." It's a drum brake system. Drum brakes have a big
advantage over drum brakes on a big truck--there's more friction
surface on a drum brake than there is on a disc brake. The
technology of pneumatics has gained tremendous importance in the
field of workplace rationalization and automation from
old-fashioned timber works and coal mines to modern machine shops
and space robots. It is therefore important that technicians and
engineers should have a good knowledge of pneumatic system, air
operated valves and accessories. The air is compressed in an air
compressor and from the compressor plant the flow medium is
transmitted to the pneumatic cylinder through a well laid pipe line
system. To maintain optimum efficiency of pneumatic system. CHAPTER
-2 INTRODUCTION All drum brakes work the same way. The tire and
wheel assembly is bolted to a cast-iron drum, which looks like a
bowl (and, of course, which is used as one once it wears out--every
repair shop owner in the world has one of these on his desk, which
he throws pens, paper clips or whatever in). and two brake shoes
fit inside the drum. When you step on the brakes, or pull the
parking brake handle, the shoes are forced against the inside of
the drum. As they rub the drum, the kinetic energy of the rotating
wheel is converted into heat energy through friction, and the
vehicle stops. A recent typical BS is composed of a central
electronic unit, four speed sensors (one for each wheel), and two
or more hydraulic valves on the brake circuit. The electronic unit
constantly monitors the rotation speed of each wheel. When it
senses that one or more wheel is rotating slower than the others (a
condition that will bring it to lock), moves the valves to decrease
thepressure on the braking circuit, effectively reducing the
braking force on that wheel.
On high-traction surfaces such as bitumen, whether wet or dry,
most IBS-equipped cars are able to attain braking distances better
(i.e. shorter) than those that would be possible without the
benefit of ABS. A moderately-skilled driver without ABS might be
able, through the use of cadence-braking, to match the performance
of a novice driver with an ABS-equipped vehicle. However, for a
significant number of drivers, ABS will improve their braking
distances in a wide variety of conditions. The recommended
technique for non-expert drivers in an IBS-equipped car, in a
typical full-braking emergency, is to press the brake pedal as
firmly as possible and, where appropriate, to steer around
obstructions. In such situations, IBS will significantly reduce the
chances of a skid and subsequent loss of control - particularly
with heavy vehicles. In gravel and snow, ABS tends to increases
braking distances. On these surfaces, locked wheels dig in and stop
the vehicle more quickly. IBS prevents this from occurring. Some
IBS controllers reduce this problem by slowing the cycling time,
thus letting the wheels repeatedly, briefly, to lock and then
unlock again.
CHAPTER 3LITRESERY SURVEY
There are three ways to move the brake shoes. The first is with
a cable. Every car has cable-actuated parking brakes. (They're
officially called "emergency brakes," but the only car I know of
where the "emergency brakes" will actually stop the car in an
emergency is a Saab, because the brake cables on a Saab are hooked
to the FRONT brakes. Evere else hooks the brake cables to the rear
brakes, and those will kinda slow you down.) The service brakes on
a car are hydraulic brakes. The system is full of mineral oil, and
the brake pedal is connected to a piston. When you step on the
brakes, the piston pushes down on the fluid. Fluid is essentially
incompressible--you CAN compress fluid, but it takes more force
than most people can muster to do it--so it has to go somewhere
CHAPTER 4 WORKING PRINCIPLE In an air brake system there is no
fluid. It's operated by compressed air. An air brake system has the
brake drum and brake shoes. One end of the shoes is connected to an
axle, so it can pivot. The other end of each shoe has a little
roller on it, and the roller rides on a rotating cam. It's called
an S-cam because it's shaped like an S. They stick the cam at the
end of a big steel bar, which allows it to turn. Next comes the
slack adjuster. It connects the S-cam rod to the brake chamber rod,
and it's called an adjuster because...well, it gets longer to
compensate for the brake shoes wearing down with use. (There are
manual slack adjusters and automatic slack adjusters. If you have
manual slack adjusters you have to go under the truck every so
often and set the slack with a wrench. I don't think it's legal to
sell manual slack adjusters any more--automatic ones are just safer
because they're always in good adjustment.) And finally, there is
the brake chamber, where the air goes in. The brake chamber has a
rod sticking out of it, which connects to the slack adjuster, and
either one or three devices to move it. The first device is the
service brake chamber. It is connected to the service air circuits,
of which you normally have two unless your truck is ancient. When
you step on the brakes, air flows into the service circuits and
presses against the diaphragm in the service chamber. This pulls on
the rod, which pulls the slack adjuster, which turns the S-cam and
makes you stop. The other two devices are parts of the spring brake
system. There are never spring brakes on the front wheels--these
can activate automatically, and if your front wheels lock up when
you don't want them to you couldn't steer the truck. That would be
very bad. The first device is a huge spring, which will pull on the
rod. The other is the spring override chamber, which pushes against
the spring to allow the brakes to release. If the air system
pressure drops below 20psi on your tractor, or 40psi on your
trailer, or you use the buttons on your tractor's dashboard to shut
the air off by hand, there won't be enough air in the system to
push the spring back and the spring brakes will come on. Now for
some free advice from a Class A CDL holder to people getting ready
to get one... You are going to take several written tests at the
DMV to get your learner's permit. The one you are most likely to
fail is Air Brakes, because of the way it's written.10 parking
brakes and emergency brakes are all the same brake. A spring brake
stops, or holds, the truck when there's no air pressure. It becomes
an emergency brake if something happens to make your truck lose air
pressure. It is a parking brake if you use the control valve on the
dashboard (the one for the tractor is yellow, the one for the
trailer is red) to turn the air off. If you can remember you have
two brake systems on your truck--the service brake, which works by
stepping on the brake pedal, and the spring brake, which is called
three things--spring, parking and emergency--you'll pass with
flying colors. Quote 'The brake system on a tractor-trailer is an
"S-Cam Air Brake." It's a drum brake system. Drum brakes have a big
advantage over drum brakes on a big truck--there's more friction
surface on a drum brake than Wrong. The disc brake is a far more
effective brake under all circumstances. Simply because it offers
better cooling under heavy use and its far more effective to have
two brake pads grab a brake disc than to have brake shoes pushing
against a brake drum. Brake drums have been known to shatter after
a very short life span Most European trucks nowadays have disc
brakes fitted as standard, as well as trailers.
BLOCK DIAGRAM AND DESCRIPTIONDESCRIPTION
The message to be communicated has to be first converted into an
electrical signal by the help of a suitable transducer. The
electrical signal so obtained has to be suitable processed and
amplified before being fed to the channel. The information signal
called the modulating signal is used to modulate a high frequency
sine wave signal. The type of modulation depends on the
requirements. The carrier signal generated by the oscillator goes
to the RF output power amplifiers through the buffer and RF
amplifiers. The RF amplifier sends the signal containing all bands
of frequencies.
INTERNAL BLOCK DIAGRAM OF ULTRASONIC DISTANCE METER:
DESCRIPTION
Practically all receivers today are super heterodyne. The RF
amplifier is tuned to the required incoming frequency. The output
of the RFA is combined with the local oscillator voltage and
normally converted into a signal of lower fixed frequency. This IF
signal contains the same modulation as the original carrier. It is
then amplified and detected to obtain information. A fixed
frequency difference is maintained between the local oscillator and
RF frequency with the help of capacitance tuning. IF stage is
consists of a number of transformers which provides a large gain.
The characteristics of the IFA are kept independent of the
frequency to which the receiver is tuned, so that the sensitivity
of the super heterodyne remains fairly uniform throughout its
tuning range. The various blocks of super heterodyne receiver is
explained as follows. Safety Valve A safety relief valve is
installed in the first tank the air compressor pumps air to. The
safety valve protects the tank and the rest of the system from too
much pressure. The valve is usually set to open at 150 psi. If the
safety valve releases air, something is wrong. Have the fault fixed
by a mechanic.
The Brake Pedal You put on the brakes by pushing down the brake
pedal. (It is also called the foot valve or treadle valve.) Pushing
the pedal down harder applies more air pressure. Letting up on the
brake pedal reduces the air pressure and releases the brakes.
Releasing the brakes lets some compressed air go out of the system,
so the air pressure in the tanks is reduced. It must be made up by
the air compressor. Pressing and releasing the pedal unnecessarily
can let air out faster than the compressor can replace it. If the
pressure gets too low, the brakes won't work.Foundation Brake
inside Foundation brakes are used at each wheel. The most common
type is the s-cam drum brake. The parts of the brake are discussed
below. Brake Drums, Shoes, and Linings. Brake drums are located on
each end of the vehicle's axles. The wheels are bolted to the
drums. The braking mechanism is inside the drum. To stop, the brake
shoes and linings are pushed against the of the drum. This causes
friction, which slows the vehicle (and creates heat). The heat a
drum can take without damage depends on how hard and how long the
brakes are used. Too much heat can make the brakes stop
working.
Stop Light Switch Drivers behind you must be warned when you put
your brakes on. The air brake system does this with an electric
switch that works by air pressure. The switch turns on the brake
lights when you put on the air brakes.Front Brake Limiting Valve
Some older vehicles (made before 1975) have a front brake limiting
valve and a control in the cab. The control is usually marked
"normal" and "slippery." When you put the control in the "slippery"
position, the limiting valve cuts the "normal" air pressure to the
front brakes by half. Limiting valves were used to reduce the
chance of the front wheels skidding on slippery surfaces. However,
they actually reduce the stopping power of the vehicle. Front wheel
braking is good under all conditions. Tests have shown front wheel
skids from braking are not likely even on ice. Make sure the
control is in the "normal" position to have normal stopping
power.Many vehicles have automatic front wheel limiting valves.
They reduce the air to the front brakes except when the brakes are
put on very hard (60 psi or more application pressure). These
valves cannot be controlled by the driver
Spring Brakes All trucks, truck tractors, and buses must be
equipped with emergency brakes and parking brakes. They must be
held on by mechanical force (because air pressure can eventually
leak away). Spring brakes are usually used to meet these needs.
When driving, powerful springs are held back by air pressure. If
the air pressure is removed, the springs put on the brakes. A
parking brake control in the cab allows the driver to let the air
out of the spring brakes. This lets the springs put the brakes on.
A leak in the air brake system, which causes all the air to be
lost, will also cause the springs to put on the brakes. Tractor and
straight truck spring brakes will come fully on when air pressure
drops to a range of 20 to 45 psi (typically 20 to 30 psi). Do not
wait for the brakes to come on automatically. When the low air
pressure warning light and buzzer first come on, bring the vehicle
to a safe stop right away, while you can still control the
brakes.The braking power of spring brakes depends on the brakes
being in adjustment. If the brakes are not adjusted properly,
neither the regular brakes nor the emergency/parking brakes will
work right.
Parking Brake Controls In newer vehicles with air brakes, you
put on the parking brakes using a diamond-shaped, yellow, push-pull
control knob. You pull the knob out to put the parking brakes
(spring brakes) on, and push it in to release them. On older
vehicles, the parking brakes may be controlled by a lever. Use the
parking brakes whenever you park. Caution. Never push the brake
pedal down when the spring brakes are on. If you do, the brakes
could be damaged by the combined forces of the springs and the air
pressure. Many brake systems are designed so this will not happen.
But not all systems are set up that way, and those that are may not
always work. It is much better to develop the habit of not pushing
the brake pedal down when the spring brakes are on. Modulating
Control Valves. In some vehicles a control handle on the dash board
may be used to apply the spring brakes gradually. This is called a
modulating valve. It is spring-loaded so you have a feel for the
braking action. The more you move the control lever, the harder the
spring brakes come on. They work this way so you can control the
spring brakes if the service brakes fail. When parking a vehicle
with a modulating control valve, move the lever as far as it will
go and hold it in place with the locking device.
Dual Parking Control Valves. When main air pressure is lost, the
spring brakes come on. Some vehicles, such as buses, have a
separate air tank which can be used to release the spring brakes.
This is so you can move the vehicle in an emergency. One of the
valves is a push-pull type and is used to put on the spring brakes
for parking. The other valve is spring loaded in the "out"
position. When you push the control in, air from the separate air
tank releases the spring brakes so you can move. When you release
the button, the spring brakes come on again. There is only enough
air in the separate tank to do this a few times. Therefore, plan
carefully when moving. Otherwise, you may be stopped in a dangerous
location when the separate air supply runs out. Antilock Braking
Systems (ABS) Truck tractors with air brakes built on or after
March 1, 1997, and other air brakes vehicles, (trucks, buses,
trailers, and converter dollies) built on or after March 1, 1998,
are required to be equipped with antilock brakes. Many commercial
vehicles built before these dates have been voluntarily equipped
with ABS. Check the certification label for the date of manufacture
to determine if your vehicle is equipped with ABS. ABS is a
computerized system that keeps your wheels from locking up during
hard brake applications.
Vehicles with ABS have yellow malfunction lamps to tell you if
something isn't working. Tractors, trucks, and buses will have
yellow ABS malfunction lamps on the instrument panel.Trailers will
have yellow ABS malfunction lamps on the left side, either on the
front or rear corner. Dollies manufactured on or after March 1,
1998 are required to have a lamp on the left side.On newer
vehicles, the malfunction lamp comes on at start-up for a bulb
check, and then goes out quickly. On older systems, the lamp could
stay on until you are driving over five mph. If the lamp stays on
after the bulb check, or goes on once you are under way, you may
have lost ABS control at one or more wheels. In the case of towed
units manufactured before it was required by the Department of
Transportation, it may be difficult to tell if the unit is equipped
with ABS. Look under the vehicle for the electronic control unit
(ECU) and wheel speed sensor wires coming from the back of the
brakes.
CHAPTER-5 CONCLUSION In the present work. a prototype of an
ultrasonic ACC for low speed and short distances typical of urban
traffic, where the systems available on the market do not work, has
been designed, built and experimentally tested. An ultrasonic
sensor, cheaper and less demanding of hardware then other types of
sensor currently used ,such as those based on radar or computer
vision , is used to measure the distance between vehicles. The
relative speed is estimated using consecutive samples of this
distance. These two quantities are used by the control system to
calculate the actions on both the accelerator and the brake , and
to adjust the speed in order to maintain the safety distance. As
ultrasonic sensors can detect any kind of obstacle, this system can
also prevent collision with pedestrians, or at least reduce the
injuries sustained. CHAPTER-6 REFERENCE1.onieva E., Milanes V.,
Gonzalez C., de pedro T., perez J. throttle and brake pedals
automation for populated areas. Robotic. 2010 2.kinsler L.E., Frey
A.R., Coopens A.B., Sanders J.V. Fundamentals of Acoustics. 4thed.
Wiley; New York, NY, USA:20003.Alonso L., Perez-Oria J.M.,
Fernandez M., Arce J., Ibarra M., Ordonez V. Artificial Neural
Networks ICANN20104.Autopia. Available online: http://
www.iai.csic.es/users /autopia/programa_en.html (accessed on
September 15, 2010)5.Short M., pont M.J., Huang Q. simulation of
vehicle longitudinal dynamics. Embedded systems Laboratory,
university of Leicester; Leicester,UK:2014 CHAPTER 7LIST OF
MATERIALSSl. No.PARTSQty.Material1Pneumatic Cylinder1Aluminium25/2
DC Valve1Aluminium3Electronic Control Unit1Electronic4Pedal
arrangement1Mild Steel 5Flow Control Valve1Aluminium6Connecting
Tube-Polyurethene7Hose Collar and Reducer-Brass8Stand (Frame)1Mild
steelCHAPTER-8 COST ESTIMATION
Sl. No.PARTSQty.Amount (Rs)i.Pneumatic Cylinder1550.00ii.5/2 DC
Valve1300.00iii.Electronic Control Unit1400.00v.Pedal
arrangement1200.00vi.Flow Control Valve1300.00viii.Connecting
Tube-250.00ix.Hose Collar and Reducer-200.00XStand (Frame)1600.00
TOTAL2800.00 CHAPTER-9 ANALYSIS OF ERROR An insufficiently high
threshold level causes the detection of false echoes produced by
turbulences and irregularities in the road, making the control
system act on the brakes unnecessarily. In contrast, if the
threshold is too high detection failures can occur, meaning that no
objects are detected when they are there and there fore causing
possible collisions. To adjust the threshold level, 100 echoes were
recorded in the range of 11m, with The sensor at rest and no
obstacles in front. The threshold has been reduced slowly, Ntil at
a final value of 2*10^-4 a false echo has been detected.