AUTOMATIC PNEUMATIC BRAKING AND BUMPER SYSTEM Submitted in partial fulfillment of the requirement for the award of DIPLOMA IN MECHANICAL ENGINEERING BY
Under the guidance of
------------------------
2005-2006 DEPARTMENT OF MECHANICAL ENGINEERING
CERTIFICATE
Register number : _________________________
This is to certify that the project report titled “PNEUMATIC BUMPER FOR FOUR WHEELER” submitted by the following students for the award of Diploma engineering is record of bonafide work carried out by them.
Done by Mr. /Ms._______________________________
In partial fulfillment of the requirement for the award of Diploma in Mechanical Engineering During the Year – (2004-2005) _________________ Head of Department
_______________ Guide
Coimbatore –641651. Date: Submitted for the university examination held on ___________
_________________ Internal Examiner Examiner
________________ External
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ACKNOWLEDGEMENT ---------------------------------------------------------------------------------
ACKNOWLEDGEMENT
At this pleasing moment of having successfully completed our project, we wish to convey our sincere thanks and gratitude to the management of our
college
and
our
beloved
chairman
…………………………………………………, who provided all the facilities
to us.
We would like to express our sincere thanks to our
principal
forwarding us
………………………………………, to
do our
for
project and offering
adequate duration in completing our project. We are also grateful to the Head of Department Prof.
……………………………………..,
for
her
constructive suggestions & encouragement during our project. With deep sense of gratitude, we extend our earnest
&
sincere
thanks
to
……………………………………………………..,
our
guide
Department
of
Mechanical
for
her
kind
guidance
&
encouragement during this project. We also express our indebt thanks to our TEACHING MECHANICAL
and
NON
TEACHING
ENGINEERING
……………………….(COLLEGE NAME).
staffs
of
DEPARTMENT,
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PNEUMATIC BUMPER FOR FOUR WHEELER -------------------------------------------------------------------------------------
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CONTENTS ---------------------------------------------------------------------------------
CONTENTS
ADKNOWLEDGEMENT
1.
SYNOPSIS
2.
INTRODUCTION
3.
LITERATURE SURVEY
4.
TYPES OF BRAKING
5.
IR SENSOR
6.
PROXIMITY SENSOR
7.COMPONENTS AND DESCRIPTION
8.
BLOCK DIAGRAM
9.WORKING PROCEDURE
10.
PROGRAM
11.
APPLICATION AND ADVANTAGES
12.
LIST OF MATERIAL
13.
COST ESTIMATION
14.
CONCLUSION
BIBLIOGRAPHY PHOTOGRAPHY
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Chapter-1
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SYNOPSIS --------------------------------------------------------------------------------CHAPTER-1 SYNOPSIS
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 aim is to design and develop a control system based an intelligent electronically controlled automotive bumper activation system is
called
“AUTOMATIC
PNEUMATIC
BRAKING
AND
BUMPER
SYSTEM”. This system is consists of IR transmitter and Receiver circuit, Control Unit, Pneumatic bumper system. The IR sensor is used to detect the obstacle. There is any obstacle closer to the vehicle (with in 4 feet), the control signal is given to the bumper activation system. The pneumatic bumper system is used to product the man and vehicle. This bumper activation system is only activated the vehicle speed above 40-50 km per hour. This vehicle speed is sensed by the proximity sensor and this signal is given to the control unit and pneumatic bumper activation system.
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Chapter-2 ---------------------------------------------------------------------------------------
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INTRODUCTION ---------------------------------------------------------------------------------
CHAPTER-2 INTRODUCTION
We have pleasure in introducing our new project “AUTOMATIC PNEUMATIC BUMPER”, which is fully equipped by IR sensors circuit and Pneumatic bumper activation circuit. It is a genuine project which is fully equipped and designed for Automobile vehicles. This forms an integral part of best quality. This product underwent strenuous test in our Automobile vehicles and it is good.
NEED FOR AUTOMATION:
Automation can be achieved through computers, hydraulics, pneumatics, robotics, etc., of these sources, pneumatics form an attractive medium for low cost automation. The main advantages of all pneumatic systems are economy and simplicity. Automation plays an important role in mass production.
For mass production of the product, the machining operations decide the sequence of machining. The machines designed for producing a particular product are called transfer machines. The components must be moved automatically from the bins to various machines sequentially and the final component can be placed separately for packaging. Materials can also be repeatedly transferred from the moving conveyors to the work place and vice versa.
Nowadays almost all the manufacturing process is being atomized in order to deliver the products at a faster rate. The manufacturing operation is being atomized for the following reasons.
To achieve mass production To reduce man power To increase the efficiency of the plant To reduce the work load To reduce the production cost To reduce the production time To reduce the material handling To reduce the fatigue of workers To achieve good product quality
Less Maintenance
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Chapter-3 ---------------------------------------------------------------------------------------
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LIERATURE SURVEY
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CHAPTER-3 LITERATURE SURVEY
SAFETY SYSTEM:
The aim is to design and develop a control system based on pneumatic breaking system of an intelligent electronically controlled automotive braking system. Based on this model, control strategies such as an 'antilock braking system' (ABS) and improved maneuverability via individual wheel braking are to be developed and evaluated.
There have been considerable advances in modern vehicle braking systems in recent years. For example, electronically controlled ABS for emergency braking, electronically controlled hydraulically actuated individual brake-by-wire (BBW) systems for saloon cars and electronically controlled pneumatically actuated systems for heavy goods vehicles. The work of recent years shall form the basis of a system design approach to be implemented. The novelty of the proposed research programmed shall lie in the design and evaluation of control systems for achieving individual wheel motion control facilitated by BBW. In the case of BBW the brake pedal is detached from the hydraulic system and replaced by a
'brake pedal simulator'. The simulator provides an electrical signal for the electronic control system.
Preliminary modeling and simulation work considers a quarter cars initially followed by a natural progression to the half car and full four wheel station cases. The model is to be constructed in modular form thus allowing the replacement / interchange of the various blocks and their associated technologies. Upon completion of the full vehicle braking model, sensitivity analyses will be carried out. Once the preliminary simulation model has been thoroughly benchmarked and existing control system strategies evaluated, an audit of the technology used is to take place and this will provide a basis for comparison of iterative technologies / techniques.
The final phase of the new modern vehicle shall include: •
Development of improved ABS control systems
•
Development and assessment of an electro-hydraulic-BBW (EH-BBW) system
•
Individual wheel braking combined with traction control
•
Assessing sensor failure and fault tolerant control system design
•
Preliminary studies into an electrically actuated system
•
Re-engineering using simplified models.
PNEUMATICS
The word ‘pneuma’ comes from Greek and means breather wind. The word pneumatics is the study of air movement and its phenomena is derived from the word pneuma. Today pneumatics is mainly understood to means the application of air as a working medium in industry especially the driving and controlling of machines and equipment.
Pneumatics has for some considerable time between used for carrying out the simplest mechanical tasks in more recent times has played a more important role in the development of pneumatic technology for automation. Pneumatic systems operate on a supply of compressed air which must be made available in sufficient quantity and at a pressure to suit the capacity of the system. When the pneumatic system is being adopted for the first time, however it wills indeed the necessary to deal with the question of compressed air supply.
The key part of any facility for supply of compressed air is by means using reciprocating compressor. A compressor is a machine that takes in air, gas at a certain pressure and delivered the air at a high pressure.
Compressor capacity is the actual quantity of air compressed and delivered and the volume expressed is that of the air at intake conditions namely at atmosphere pressure and normal ambient temperature.
The compressibility of the air was first investigated by Robert Boyle in 1962 and that found that the product of pressure and volume of a particular quantity of gas. The usual written as PV = C
(or) PıVı = P2V2
In this equation the pressure is the absolute pressured which for free is about 14.7 Psi and is of courage capable of maintaining a column of mercury, nearly 30 inches high in
an ordinary barometer. Any gas can be used in pneumatic system but air is the mostly used system now a days.
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Chapter-4 ---------------------------------------------------------------------------------------
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TYPES OF BRAKING ---------------------------------------------------------------------------------
CHAPTER-4 TYPES OF BRAKING The brakes for automotive use may be classified according the following considerations.
1.
PURPOSE
2.
LOCATION
3.
CONSTRUCTION
4.
METHOD OF ACTUATION
5.
EXTRA BRAKING EFFORT
Based on the above considerations, brakes are classified with respect to following factors.
1. With respect to application, a.
Foot brake
b.
Hand brake
2. With respect to the number of wheels,
a.
Two wheel brakes
b.
Four wheel brakes
3. With respect to the method of braking contact a.
Internal expanding brakes
b.
External contracting brakes
4. With respect to the method of applying the braking force. a.
Single acting brake
b.
Double acting brakes.
5. With respect to the brake gear, a.
Mechanical brake
b.
Power brakes
6. With respect to the nature of power employed a.
Vacuum brake
b.
Air brake
c.
Hydraulic brake
d.
Hydrostatic brake
e.
Electric brake
7. With respect to power transmission, a.
Direct acting brakes
b.
Geared brakes
8. With respect to power unit, a.
Cylinder brakes
b.
Diaphragm brake
The foot brake or service brake is always applied by a pedal, while the parking brake is applied by a hand lever. The parking brake is intended chiefly to hold the car in position. The parking brake can be set in the “ON” position by means of a latch while the service brake remains on only as long as the driver presses down on the pedal.
The hand brake is normally used only after the driver has stopped the car by using the foot brake. Its other use is as an emergency brake to stop the car if the foot braked system should fail. The hand or parking brakes operates on a pair of wheels, frequently the rear wheels. When drum type rear brakes are used, the same shoes can be used for both hand and foot control.
The drum type of brake may either be a band brake or a shoe brake. Both band brakes and shoe brakes may be either external or internal. The band brakes generally are external and shoe brakes internal. In drum brakes the drum is attached to the wheel and revolves with it. Friction to slow the drum is applied from inside by the shoes which do not rotate but are mounted on a stationary metal back plate. There are different types of drum brakes such as a two leading shoe arrangement – which gives an augmented response to pedal effort because of its self applying arrangement. A leading-trailing shoe is a cheaper and better alternative as it is equally effective whether the car is going forward or backwards.
Manufacturers design drum brakes so that rain, show or ice or grit cannot get inside and decrease braking efficiency for moisture greatly reduces the friction between the linings and the drum.
The dissipate quickly the considerable amount of heat generated when braking a fast moving heavy car large brake drums would be required. Disc brakes do the job more efficiently, for the cooling air can get to the rubbing between each piston and the disc, there is a friction pad held in position by retaining pins, spring plates etc. Passages are drilled in the caliper for the fluid to enter or leave the each housing. These passages are also
connected to another one for bleeding. Each cylinder contains a rubber selling ring between the cylinder and the piston.
The brakes are applied, hydraulically actuated piston move the friction pads into contact with the disc, applying equal and opposite forces on the later. On releasing the brakes, the rubber sealing rings act as return springs and retract the pistons and the friction pads away from the disc.
Now let us see in detail about different braking systems in automobiles.
MECHANICAL BRAKE:
In a motor vehicle, the wheel is attached to an auxiliary wheel called drum. The brake shoes are made to contact this drum. In most designs, two shoes are used with each drum to form a complete brake mechanism at each wheel. The brake shoes have bake linings on their outer surfaces. Each brake shoe is hinged at one end by on anchor pin; the other end is operated by some means so that the brake shoe expands outwards. The brake linings come into contact with the drum. Retracting spring keeps the brake shoe into position when the brakes are not applied. The drum encloses the entire mechanism to keep out dust and moisture. The wheel attaching bolts on the drum are used to contact wheel and drum. The braking plate completes the brake enclosure, holds the assembly to car axie, and acts the base for fastening the brake shoes and operating mechanism. The shoes are
generally mounted to rub against the inside surface of the drum to form as internal expanding brake as shown in the figure.
HYDRAULIC BRAKES:
The hydraulic brakes are applied by the liquid pressure.
The pedal force is
transmitted to the brake shoe by means of a confined liquid through a system of force transmission.
The force applied to the pedal is multiplied and transmitted to brake shoes by a force transmission system. This system is based upon Pascal’s principle, which states that “The confined liquids transmit pressure without loss equally in all directions”.
It essentially consists of two main components – master cylinder and wheel cylinder the master cylinder is connected by the wheel cylinders at each of the four wheels. The system is filled with the liquid under light pressure when the brakes are not in operation. The liquid is known as brake fluid, and is usually a mixture of glycerin and alcohol or caster-oil, denatured alcohol and some additives Spring pressure, and thus the fluid pressure in the entire system drops to its original low valve, which allows retracting spring on wheel brakes to pull the brake shoes out of contact with the brake drums into their original positions. This causes the wheel cylinder piston also to come back to its original inward position. Thus, the brakes are released.
AIR BRAKE:
Air brakes are widely used in heavy vehicle like buses and trucks which require a heavier braking effort that can be applied by the driver’s foot. Air brakes are applied by the pressure of compressed air, instead of foot pressure, acting against flexible diaphragms in brake chamber. The diaphragms are connected to the wheel brakes. These diaphragms are controlled through a hand or foot operated valve. The brake valve controls brake operation by directing the flow of air from a reservoir against diaphragms in the brake chamber when the brakes are applied and from brake chambers to tube atmosphere when the brakes are released. The air compressor, driven by the engine furnishes compressed air to the reservoir fall below a set valve.
ELECTRIC BRAKE:
Electric Brakes are also used in some motor vehicles, although these are not very popular. Warner electric brake is one of the examples of such brakes. An electric brake essentially consists of an electromagnet within the brake drum. The current from the battery is utilized to energize the electromagnet, which actuates the mechanism to expand the brake shoe against the brake drum, thus applying the brakes. The severity of braking is controlled by means of a rheostat, which is operated by the driver through the foot pedal.
Electric brakes are simpler. These brakes do not require complicated operating linkage. Only cable is required to take current from the battery to the electromagnet. Also, these are very quick in action as compared to other types of brakes.
VACUUM BRAKES / SERVO BRAKES:
A serve mechanism fitted to the braking system reduces the physical effort the driver has to use on the brake pedal most servo mechanisms are of the vacuum assistance type. A pressure differential can be established by subjecting one side of the piston to atmospheric pressure and the other side to a pressure below atmospheric pressure by exhausting air from the corresponding end of the servo cylinder.
REGENERATIVE BRAKING:
Electricity powered vehicles use regenerative braking for stopping the vehicle. With regenerative braking pressing the brake pedal does not necessarily activate a conventional friction brake. The motor controller controlling the vehicle is treated as a generator which slows the vehicle and simultaneously provides an output for charging the battery. The effectiveness of regenerative braking falls of with vehicle speed. Electric vehicles will have to be fitted with conventional hydraulic friction brakes as well as with regenerative systems.
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Chapter-5 ---------------------------------------------------------------------------------------
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IR SENSOR ---------------------------------------------------------------------------------
CHAPTER-5 IR SENSOR SENSORS A sensor is a transducer used to make a measurement of a physical variable. Any sensor requires calibration in order to be useful as a measuring device. Calibration is the procedure by which the relationship between the measured variable and the converted output signal is established.
Care should be taken in the choice of sensory devices for particular tasks. The operating characteristics of each device should be closely matched to the task for which it is being utilized. Different sensors can be used in different ways to sense same conditions and the same sensors can be used in different ways to sense different conditions.
TYPES OF SENSOR: Passive sensors detect the reflected or emitted electro-magnetic radiation from natural sources, while active sensors detect reflected responses from objects which are irradiated from artificially generated energy sources, such as radar. Each is divided further in to non-scanning and scanning systems.
A sensor classified as a combination of passive, non-scanning and non-imaging method is a type of profile recorder, for example a microwave radiometer. A sensor classified as passive, non-scanning and imaging method, is a camera, such as an aerial survey camera or a space camera, for example on board the Russian COSMOS satellite. Sensors classified as a combination of passive, scanning and imaging are classified further into image plane scanning sensors, such as TV cameras and solid state scanners, and object plane scanning sensors, such as multi-spectral scanners (optical-mechanical scanner) and scanning microwave radiometers. An example of an active, non-scanning and non-imaging sensor is a profile recorder such as a laser spectrometer and laser altimeter. An active, scanning and imaging sensor is radar, for example synthetic aperture radar (SAR), which can produce high resolution, imagery, day or night, even under cloud cover. The most popular sensors used in remote sensing are the camera, solid state scanner, such as the CCD (charge coupled device) images, the multi-spectral scanner and in the future the passive synthetic aperture radar. Laser sensors have recently begun to be used more frequently for monitoring air pollution by laser spectrometers and for measurement of distance by laser altimeters.
CHARACTERISTICS OF OPTICAL SENSOR:
Optical sensors are characterized specified by spectral, radiometric and geometric performance The spectral characteristics are spectral band and band width, the central wavelength, response sensitivity at the edges of band, spectral sensitivity at outer wavelengths and sensitivity of polarization. Sensors using film are characterized by the sensitivity of film and the transmittance of the filter, and nature of the lens. Scanner type sensors are specified by the spectral characteristics of the detector and the spectral splitter. In addition, chromatic aberration is an influential factor. The radiometric characteristics of optical sensors are specified by the change of electro-magnetic radiation which passes through an optical system. They are radiometry of the sensor, sensitivity in noise equivalent power, dynamic range, signal to noise ratio (S/N ratio) and other noises, including quantification noise. The geometric characteristics are specified by those geometric factors such as field of view (FOV), instantaneous field of news (IFOV), band to band registration, MTF, geometric distortion and alignment of optical elements.
IFOV is defined as the angle contained by the minimum area that can be detected by a scanner type sensor. For example in the case of an IFOV of 2.5 milli radians, the detected area on the ground will be 2.5 meters x 2.5 meters, if the altitude of sensor is 1,000 m above ground.
In our project IR transmitter and IR receiver are used to detect the obstacle. These sensors are fitted at the front side of the vehicle.
IR TRANSMITTER: The IR transmitting circuit is used in many projects. The IR transmitter sends 40 kHz (frequency can be adjusted) carrier under 555 timer control. IR carriers at around 40 kHz carrier frequencies are widely used in TV remote controlling and ICs for receiving these signals are quite easily available.
IR RECEIVER: The transmitted signal reflected by the obstacle and the IR receiver circuit receives the signal and giving control signal to the control unit. The control unit activates the pneumatic breaking system, so that break was applied.
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Chapter-6 ---------------------------------------------------------------------------------------
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COMPONENTS AND DESCRIPTION -----------------------------------------------------------------------------------------
CHAPTER-6 PROXIMITY SENSORS
Infrared proximity sensors Infrared proximity sensors work by sending out a beam of IR light, and then computing the distance to any nearby objects from characteristics of the returned (reflected) signal. There are a number of ways to do this, each with its own advantages and disadvantages:
Reflected IR strength
You could build a simple IR proximity sensor out of essentially just an IR LED and IR photodiode. This simple sensor, though, would be prey to background light (i.e., your IR "receiver" would be responding to naturally present IR as well as reflected IR).
Modulated IR signal A better solution would be to modulate your transmitted IR (i.e., to send out a rapidly-varying IR signal), and then have the receive circuitry only respond to the level of the received, matching, modulated IR signal (i.e., to ignore the DC component of the received signal, and only trigger off the AC component). This method, though, is still at the mercy of the characteristics (in particular, IR reflectance) of the obstacle you're trying to sense.
Triangulation The best way to use IR to sense an obstacle is to sense the angle at which the reflected IR is returned to your sensor. By use of a bit of trigonometry, you can then compute distance, knowing the location of your transmit and receive elements. Needless to say, this isn't a simple sensor to build yourself. You're probably money ahead by just buying an IR proximity sensor with this logic built in. One I particularly like is the Sharp GP2D15 IR Ranger. It has a built-in detection range of 24 cm (this keeps its cost, and the complexity of your interface circuitry down), is reasonably priced, and is available from Acroname. Acroname also has an interesting article covering the operation and utilization of all the impressive Sharp IR sensors here. The GP2D15 interface is 3-wire with power, ground and the output voltage (the sensor outputs Vcc when it sees something at 24 cm distance); it requires 4.5 - 5.5 V power for operation, and eats about 50 mA of current as long as it is powered. So its advantages are (1) its simple interface, and (2) easy, reliable sensing of obstacles at a distance. Its disadvantages are (1) its requirement for 5 V power, and (2) its requirement for 50 mA of current regardless of whether anything is being sensed (neither of these recommend this sensor for solar-powered 'bots). If your BEAMbot's circuitry has provision for a "touch-switch" contact sensor, the GP2D15 can easily be used instead, with the addition of an NPN transistor:
Acoustic proximity sensors
One oft-used method (at least on larger, pricier 'bots) of avoiding hazards is via sonar ranging. Here, acoustic signals ("ping"s) are sent out, with the time of echo return being a measure of distance to an obstacle. This does, unfortunately, require fairly accurate timing circuitry -- so acoustic sensors really require a processor of some sort to drive them. Also note that acoustic sensing essentially requires the use of commercial sensors, there's no real way to "homebrew" something from scratch. The most common acoustic proximity sensor is the kind used in polaroid cameras. For details on these, I'll refer you to the Acroname site's "Polaroid Sonar Ranging Primer." There's now also a "new kid on the block" -- the Devantech SRF04 UltraSonic Ranger. Acroname sells it (see their page on it here), and "Tech Geek" has a review on it here. This guy costs about twice what the Sharp IR sensors cost, but has a much wider range of sensing; it costs far less than the Polaroid acoustic rangers, is easier to interface, and draws less power.
Capacitive proximity sensors
Your 'bot can also sense its distance to objects by detecting changes in capacitance around it. When power is applied to the sensor, an electrostatic field is generated and reacts to changes in capacitance cause by the presence of a target. The main disadvantage to this sensor (often called a capaciflector) is that its usefulness is dependent on properties of the obstacles it is sensing (namely, their dialectric constant). The higher the dielectric constant (say, water), the more sensitive a capacitive sensor is to that target. The sensing distance depends on the dielectric constant of the target and the surface areas of the probe and the target.
Inductive proximity sensors
Another method for sensing distance to objects is through the use of induced magnetic fields. The primary problem with this method is that it is largely confined to sensing metallic objects.
Contact sensors (as their name implies) require physical contact with some other object in order to "trigger." While this is sometimes a bit inconvenient for your 'bot (unlike proximity sensors, contact sensors won't help a 'bot avoid an obstacle before it is within "arm's reach"), it has two big advantages: Contact sensors are very easy to build at home from various bits & pieces you probably already have lying around.
Contact sensors don't draw power until contact is made.
Obstacle avoidance contact sensors Contact sensors for obstacle avoidance are essentially the electronic version of a cat's "whiskers." In most designs, a whisker is attached to one electrical contact, and this contact gets pushed into another one if the whisker touches something. You can also just mount a "whisker" to a small pushbutton switch (you can salvage some nice "soft" ones from floppy drives).
Ian Bernstein's site has an excellent tutorial for one contact sensor design here.
Ground contact sensors Some BEAMbots may want to know when a leg touches the ground. Here, you'll need some sort of a foot contact sensor. Again, you can use a "soft" pushbutton switch (preferably salvaged) for this job. You can also build a fairly simple ground contact sensor of your own. Clifford Boerema, Jr. posted a nice design for a foot contact sensor.
Field (electric, capacitance) sensors Field sensors aren't used much in BEAMbots yet (principally because of the power and complexity some designs require). A couple, though, has been put forward to date (bear in mind that I haven't built either, so you're on your own here...): Wilf Rigter's E-sensor
The incomparable Wilf Rigter came up with an E-field detector (well, two variant designs actually) that your bot can use, Either of these (and just on a hunch, I'd suspect the 2N7000 version is easier to get parts for) should work equally well; note that the human body is a good absorber of stray RF fields, so this sensor should be a good people-detector.
Rich Caudle's capaciflector
There's more info on the capaciflector here, and a brief abstract on it here.
State sensors State sensors tell your 'bot something about its condition -- tilt, temperature, and the like. These can be used to change your 'bot's behavior in ways (ideally) that help it protect itself and get around.
Tilt switches pix/tilt_switches.jpgpix/tilt_switches.jpgpix/tilt_switches.jpg(1/4" grid) A number of types of tilt switches are commercially available -- all use some sort of moving contact (in some cases a blob of mercury, in others a metal ball) to short out various contacts. You can use these to cause your 'bot to do something special if... Your BEAMbot has flipped "upside down" Your BEAMbot is on a "dangerous" slope, and needs to turn in order to avoid rolling Your BEAMbot is attempting to climb up / down a slope that is beyond its capabilities, and needs to reverse 'Most any of these will work for you; personally, I try to avoid tilt switches containing mercury since its toxic, and generally contained in glass vials that are fairly easy to accidentally break open.
Temperature sensors Thermister, other goodies...
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Chapter-7 ---------------------------------------------------------------------------------------
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COMPONENTS AND DESCRIPTION -----------------------------------------------------------------------------------------
CHAPTER-7 COMPONENTS AND DESCRIPTION
SELECTION OF PNEUMATICS:
Mechanization is broadly defined as the replacement of manual effort by mechanical power. Pneumatics is an attractive medium for low cost mechanization particularly for sequential or repetitive operations. Many factories and plants already have a compressed air system, which is capable of providing both the power or energy requirements and the control system (although equally pneumatic control systems may be economic and can be advantageously applied to other forms of power).
The main advantages of an all-pneumatic system are usually economy and simplicity, the latter reducing maintenance to a low level. It can also have out standing advantages in terms of safety.
PNEUMATIC COMPONENTS AND ITS DESCRIPTION
The pneumatic bearing press consists of the following components to fulfill the requirements of complete operation of the machine.
1) PNEUMATIC SINGLE ACTING CYCLINDER 2) SOLENOID VALVE 3) FLOW CONTROL VALVE 4) IR SENSOR UNIT 5) WHEEL AND BRAKE ARRANGEMENT
6) PU CONNECTOR, REDUCER, HOSE COLLAR 7) STAND 8) SINGLE PHASE INDUCTION MOTOR
1) PNEUMATIC SINGLE ACTING CYLINDER:
Pneumatic cylinder consist of A) PISTON
B) CYLINDER
The cylinder is a Single acting cylinder one, which means that the air pressure operates forward and spring returns backward. The air from the compressor is passed through the regulator which controls the pressure to required amount by adjusting its knob.
A pressure gauge is attached to the regulator for showing the line pressure. Then the compressed air is passed through the single acting 3/2 solenoid valve for supplying the air to one side of the cylinder.
One hose take the output of the directional Control (Solenoid) valve and they are attached to one end of the cylinder by means of connectors. One of the outputs from the directional control valve is taken to the flow control valve from taken to the cylinder. The hose is attached to each component of pneumatic system only by connectors.
CYLINDER TECHNICAL DATA:
Piston Rod: M.S. hard Chrome plated Seals: Nitrile (Buna – N) Elastomer End Covers: Cast iron graded fine grained from 25mm to 300mm Piston: -Aluminium. Media: -Air. Temperature Range: 0^c to 85^c
Parts of Pneumatic Cylinder
Piston:
The piston is a cylindrical member of certain length which reciprocates inside the cylinder. The diameter of the piston is slightly less than that of the cylinder bore diameter
and it is fitted to the top of the piston rod. It is one of the important parts which convert the pressure energy into mechanical power.
The piston is equipped with a ring suitably proportioned and it is relatively soft rubber which is capable of providing good sealing with low friction at the operating pressure. The purpose of piston is to provide means of conveying the pressure of air inside the cylinder to the piston of the oil cylinder.
Generally piston is made up of
Aluminium alloy-light and medium work. Brass or bronze or CI-Heavy duty.
The piston is single acting spring returned type. The piston moves forward when the high-pressure air is turned from the right side of cylinder.
The piston moves backward when the solenoid valve is in OFF condition. The piston should be as strong and rigid as possible. The efficiency and economy of the machine primarily depends on the working of the piston. It must operate in the cylinder with a minimum of friction and should be able to withstand the high compressor force developed in the cylinder and also the shock load during operation.
The piston should posses the following qualities.
a. The movement of the piston not creates much noise. b. It should be frictionless. c. It should withstand high pressure.
Piston Rod
The piston rod is circular in cross section. It connects piston with piston of other cylinder. The piston rod is made of mild steel ground and polished. A high finish is essential on the outer rod surface to minimize wear on the rod seals. The piston rod is connected to the piston by mechanical fastening. The piston and the piston rod can be separated if necessary.
One end of the piston rod is connected to the bottom of the piston. The other end of the piston rod is connected to the other piston rod by means of coupling. The piston transmits the working force to the oil cylinder through the piston rod. The piston rod is designed to withstand the high compressive force. It should avoid bending and withstand shock loads caused by the cutting force. The piston moves inside the rod seal fixed in the
bottom cover plate of the cylinder. The sealing arrangements prevent the leakage of air from the bottom of the cylinder while the rod reciprocates through it.
Cylinder Cover Plates
The cylinder should be enclosed to get the applied pressure from the compressor and act on the pinion. The cylinder is thus closed by the cover plates on both the ends such that there is no leakage of air. An inlet port is provided on the top cover plate and an outlet ports on the bottom cover plate. There is also a hole drilled for the movement of the piston.
The cylinder cover plate protects the cylinder from dust and other particle and maintains the same pressure that is taken from the compressor. The flange has to hold the piston in both of its extreme positions. The piston hits the top plat during the return stroke and hits the bottom plate during end of forward stroke. So the cover plates must be strong enough to withstand the load.
Cylinder Mounting Plates:
It is attached to the cylinder cover plates and also to the carriage with the help of ‘L’ bends and bolts.
2. SOLENOID VALVE WITH CONTROL UNIT:
The directional valve is one of the important parts of a pneumatic system. Commonly known as DCV, this valve is used to control the direction of air flow in the pneumatic system. The directional valve does this by changing the position of its internal movable parts.
This valve was selected for speedy operation and to reduce the manual effort and also for the modification of the machine into automatic machine by means of using a solenoid valve. A solenoid is an electrical device that converts electrical energy into straight line motion and force. These are also used to operate a mechanical operation which in turn operates the valve mechanism. Solenoids may be push type or pull type. The push type solenoid is one in which the plunger is pushed when the solenoid is energized electrically. The pull type solenoid is one is which the plunger is pulled when the solenoid is energized.
The name of the parts of the solenoid should be learned so that they can be recognized when called upon to make repairs, to do service work or to install them.
Parts of a Solenoid Valve
1. Coil
The solenoid coil is made of copper wire. The layers of wire are separated by insulating layer. The entire solenoid coil is covered with an varnish that is not affected by solvents, moisture, cutting oil or often fluids. Coils are rated in various voltages such as 115 volts AC, 230 volts AC, 460 volts AC, 575 Volts AC, 6 Volts DC, 12 Volts DC, 24 Volts DC, 115 Volts DC & 230 Volts DC. They are designed for such frequencies as 50 Hz to 60 Hz.
2. Frame The solenoid frame serves several purposes. Since it is made of laminated sheets, it is magnetized when the current passes through the coil. The magnetized coil attracts the metal plunger to move. The frame has provisions for attaching the mounting. They are usually bolted or welded to the frame. The frame has provisions for receivers, the plunger. The wear strips are mounted to the solenoid frame, and are made of materials such as metal or impregnated less fiber cloth.
3. Solenoid Plunger
The Solenoid plunger is the mover mechanism of the solenoid. The plunger is made of steel laminations which are riveted together under high pressure, so that there will be no movement of the lamination with respect to one another. At the top of the plunger a pin hole is placed for making a connection to some device. The solenoid plunger is moved by
a magnetic force in one direction and is usually returned by spring action.
Solenoid
operated valves are usually provided with cover over either the solenoid or the entire valve. This protects the solenoid from dirt and other foreign matter, and protects the actuator. In many applications it is necessary to use explosion proof solenoids.
WORKING OF 3/2 SINGLE ACTING SOLENOID (OR) CUT OFF VALVE:
The control valve is used to control the flow direction is called cut off valve or solenoid valve. This solenoid cut off valve is controlled by the emergency push button. The 3/2 Single acting solenoid valve is having one inlet port, one outlet port and one exhaust port. The solenoid valve consists of electromagnetic coil, stem and spring. The air enters to the pneumatic single acting solenoid valve when the push button is in ON position.
Technical Data: Size
: ¼”
Pressure
: 0 to 7 kg / cm2
Media
: Air
Type
:
3/2
Applied Voltage
: 230V A.C
Frequency
: 50 Hz
3. FLOW CONTROL VALVE: 1. Technical Data: Size
: ¼”
Pressure
: 0 to 10 kg / cm2
Media
: Air (b) Purpose: This valve is used to speed up the piston movement and also it acts as an one – way
restriction valve which means that the air can pass through only one way and it can’t return back. By using this valve the time consumption is reduced because of the faster movement of the piston.
4. IR SENSOR UNIT:-
The IR transmitter and IR receiver circuit is used to sense the obstacle. It is fixed to the back side of the frame stand with a suitable arrangement. The pneumatic cylinder is controlled by the flow control valve, single acting solenoid valve and control unit.
IR TRANSMITTER CIRCUIT:
+Vcc R4 (47Ω) 3
T1 (BD140) 1
2 C3 (100µ/25V) R2 (47Ω)
150K 1
8
2
7
R1 1.5K
IC 555 R5 L1
4.7Ω IR LED
3
6
4 5 C2 0.01pF
C1 0.1pF
IR RECEIVER CIRCUIT:
1K +12V RELAY R12 (680Ω)
R1 (4.7K)
RL1 L3 (LED)
D2 1N4007
R10 4.7K
C3 (100µ) R7 (100K)
D1 (1N 4007) T5 (BC547B)
R9 (4.7K)
R8
T3 BC 557
T4 (BC 547B)
L1 (IR SENSOR) L2 (IR SENSOR)
C2 (100µ) 4.7K
R3 R2 4.7K
C4 (0.1pF)
C1 (0.01 pF)
T2 (BC549C) 120Ω
R13 120Ω
C8 (47 pF) R5 T1 (BC 549C)
R11 22K
C7 22µF (50V)
R6 2.2K
C5 (0.1pF)
AT NORMAL CONDITION:
The IR transmitter sensor is transmitting the infrared rays with the help of 555 IC timer circuit. These infrared rays are received by the IR receiver sensor. The Transistor T1, T2 and T3 are used as an amplifier section. At normal condition Transistor T5 is OFF condition. At that time relay is OFF, so that the vehicle running continuously.
AT OBSTACLE CONDITION:
At Obstacle conditions the IR transmitter and IR receiver, the resistance across the Transmitter and receiver is high due to the non-conductivity of the IR waves. So the output of transistor T5 goes from OFF condition to ON stage. In that time the relay is ON position. In that time, the solenoid valve is on so that the vehicle stops.
5. WHEEL AND BRAKING ARRANGEMENT:
The simple wheel and braking arrangement is fixed to the frame stand. Near the brake drum, the pneumatic cylinder piston is fixed.
6. PU CONNECTIORS, REDUCER AND HOSECOLLAR:
In our pneumatic system there are two types of connectors used; one is the hose connector and the other is the reducer. Hose connectors normally comprise an adapter (connector) hose nipple and cap nut. These types of connectors are made up of brass or Aluminium or hardened steel. Reducers are used to provide inter connection between two pipes or hoses of different sizes.
They may be fitted straight, tee, “V” or other
configurations. These reducers are made up of gunmetal or other materials like hardened steel etc.
7. STAND: This is a supporting frame and made up of mild steel. 8. SINGLE PHASE INDUCTION MOTOR:-
It is found to drive the roller shaft which fixed on the end of the frame structure. The free end of the shaft in the motor a large pulley is found around which the belt runs. The other specification about the motor is discussed in design part of the machine.
Single-Phase Theory Because it has but a single alternating current source, a single-phase motor can only produce an alternating field: one that pulls first in one direction, then in the opposite as the polarity of the field switches. A squirrel-cage rotor placed in this field would merely twitch, since there would be no moment upon it. If pushed in one direction, however, it would spin. The major distinction between the different types of single-phase AC motors is how they go about starting the rotor in a particular direction such that the alternating field will produce rotary motion in the desired direction. This is usually done by some device that introduces a phase-shifted magnetic field on one side of the rotor. The figure the performance curves of the four major types of single-phase AC motors. They are described below.
Split-Phase Motors: The split phase motor achieves its starting capability by having two separate windings wound in the stator. The two windings are separated from each other. One winding is used only for starting and it is wound with a smaller wire size having higher electrical resistance than the main windings. From the rotor's point of view, this time delay coupled with the physical location of the starting winding produces a field that appears to rotate. The apparent rotation causes the motor to start.
A centrifugal switch is used to disconnect the starting winding when the motor reaches approximately 75% of rated speed. The motor then continues to run on the basis of normal induction motor principles.
Capacitor-Start Motors Capacitor start motors form the largest single grouping of general purpose single phase motors. These motors are available in a range of sizes from fractional through 3HP.
The winding and centrifugal switch arrangement is very similar to that used in a split phase motor. The main difference being that the starting winding does not have to have high resistance. In the case of a capacitor start motor, a specialized capacitor is utilized in a series with the starting winding. The addition of this capacitor produces a slight time delay between the magnetization of starting poles and the running poles. Thus the appearance of a rotating field exists. When the motor approaches running speed, the starting switch opens and the motor continues to run in the normal induction motor mode. This moderately priced motor produces relatively high starting torque, 225 to 400% of full load torque. The capacitor start motor is ideally suited for hard to start loads such as conveyors, air compressors and refrigeration compressors. Due to its general overall desirable characteristics, it also is used for many applications where high starting torque may not be required.
The capacitor start motor can usually be recognized by the bulbous protrusion on the frame where the starting capacitor is located.
Permanent-Split Capacitor Motors The capacitor of this motor is left in series with the starting winding during normal operation. The starting torque is quite low, roughly 40% of full-load, so low-inertia loads such as fans and blowers make common applications. Running performance and speed
regulation can be tailored by selecting an appropriate capacitor value. No centrifugal switch is required.
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Chapter-8 ---------------------------------------------------------------------------------------
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BLOCK DIAGRAM --------------------------------------------------------------------------------CHAPTER-8 BLOCK DIAGRAM
WHEEL SPEED SENSING ARRANGEMENT
POWER SUPPLY
IR TRANSMITTER
CONTROL UNIT
IR RECEIVER
FLOW CONTROL VANVE
SOLINOID VALVE
PNEUMATIC CYLINDER AIR TANK (COMPRESSOR)
BUMPER ANGEMENT
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Chapter-9 ---------------------------------------------------------------------------------------
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WORKING OPERATION
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CHAPTER-9 WORKING OPERATION The impartant components of our project are,
• IR transmitter • IR receiver • Control Unit with Power supply • Solenoid Valve • Flow control Valve • Air Tank (Compressor)
The IR TRANSMITTER circuit is to transmite the Infra-Red rays. If any obstacle is there in a path, the Infra-Red rays reflected. This reflected Infra-Red rays are received by the receiver circuit is called “IR RECEIVER”.
The IR receiver circuir receives the reflected IR rays and giving the control signal to the control circuit. The control circuit is used to activate the solenoid valve. The operating principle of solenoid valve is already explained in the above chapter.
If the solenoid valve is activated, the compressed air passes to the Single Acting Pneumatic Cylinder. The compressed air activate the pneumatic cylinder and moves the piston rod.
If the piston moves forward, then the breaking arrangement activated. The breaking arrangement is used to break the wheel gradually or suddenly due to the pistion movement. The breaking speed is varied by adjesting the valve is called “FLOW CONTROL VALVE”.
In our project, we have to apply this breaking arrangement in one wheel as a model. The compressed air drawn from the compressor in our project. The compressed air floe through the Polyurethene tube to the flow control valve. The flow control valve is connected to the solenoid valve as mentioned in the block diagram.
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Chapter-10 ---------------------------------------------------------------------------------------
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PROGRAM -------------------------------------------------------------------------------------
CHAPTER-10 PROGRAM //#include #include #include sbit input=P1^3; sbit output=P2^0; sbit output1=P3^2; void del(); void ser_init(); void ser_out(unsigned char); void ser_dis(unsigned char*da,unsigned char no); void mob_init(); void sms_rec(); void msg_send(); void speed(); void ex_int(); unsigned char c,v[30],s,j,a,start,msec,dac,CON; unsigned int s_spd,spd,diff,kk,var,cou,R1,R2,R3,R4,CON1,siv; bit b; void main() { P2=0X00; j=1; CON=0; CON1=0; lcd_init(); ser_init(); read(0x01); read(0x80); lcd_disp(" PNUEMATIC ",16); read(0xc0); lcd_disp(" PUMBER ",16); del();del(); read(0x80); lcd_disp("SPEED: TMOD=0X21; TH0=TL0=0X00; EA=1; ET0=1;
",16);
TR0=1; siv=0; b=0; dac=150; while(1) { if(input==1&&b==0) b=1; if(input==0&&b==1) { b=0; cou++; } speed(); } } void timer0_intr() interrupt 1 { TR0=0; msec++; TR0=1; } void speed() { if(msec>=45) { TR0=0; msec=0; spd=cou*60; spd=spd/2; read(0x86); write(spd/1000+0x30); R1=(spd/1000+0x30); write(spd%1000/100+0x30); R2=(spd%1000/100+0x30); write('.'); write(spd%100/10+0x30); R3=(spd%100/10+0x30); write(spd%10+0x30); R4=(spd%10+0x30); write('K'); write('M'); cou=0;
siv++; TH0=TL0=0x00; TR0=1; if(spd>0150) { output=1; } } }
void ser_init() { TH1=0xfd; TMOD=0x20; TR1=1; delay(200); SCON=0x58; }
////TH1=0xFd; 9600 baud rate 12Mhz
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Chapter-11 ---------------------------------------------------------------------------------------
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APPLICATIONS AND ADVANTAGES -------------------------------------------------------------------------------------
CHAPTER-11 APPLICATIONS AND ADVANTAGES
APPLICATIONS • For automobile application • Industrial application
ADVANTAGES • Free from wear adjustment. • Less power consumption • It gives simplified very operation. Installation is simplified very much
DISADVANTAGES • Additional cost is required to install this arrangement in the vehicle .
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Chapter-12 ---------------------------------------------------------------------------------------
---------------------------------------------------------------------------------
LIST OF MATERIALS --------------------------------------------------------------------------------CHAPTER-12 LIST OF MATERIALS
Sl. No. i. ii. iii. iv. v. vi. vii. viii. ix. x
PARTS
Single Acting Pneumatic Cylinder Flow Control Valve Wheel Solenoid Valve Single Phase induction motor Sensor Unit Pulley Polyethylene Tube Hose Collar and Reducer Stand (Frame)
Qty. 1 1 1 1 1 1 2 1
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Chapter-13 ---------------------------------------------------------------------------------------
---------------------------------------------------------------------------------
COST ESTIMATION --------------------------------------------------------------------------------CHAPTER-13 COST ESTIMATION
MATERIAL COST:
Sl. No. i. ii. iii. iv. v. vi. vii. viii. ix. x
PARTS
Single Acting Pneumatic Cylinder Flow Control Valve Wheel Solenoid Valve Single Phase induction motor Sensor Unit Pulley Polyethylene Tube Hose Collar and Reducer Stand (Frame)
Qty. 1 1 1 1 1 1 2 1
Amount (Rs)
2. LABOUR COST LATHE, DRILLING, WELDING, GRINDING, POWER HACKSAW, GAS CUTTING: Cost = 3. OVERHEAD CHARGES
The overhead charges are arrived by “Manufacturing cost”
Manufacturing Cost =
Material Cost + Labour cost
= = Overhead Charges
= =
20% of the manufacturing cost
TOTAL COST Total cost
=
Material Cost + Labour cost + Overhead Charges
= = Total cost for this project
=
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Chapter-14 ---------------------------------------------------------------------------------------
---------------------------------------------------------------------------------
CONCLUSION ---------------------------------------------------------------------------------
CHAPTER-14 CONCLUSION
This project work has provided us an excellent opportunity and experience, to use our limited knowledge. We gained a lot of practical knowledge regarding, planning, purchasing, assembling and machining while doing this project work. We feel that the project work is a good solution to bridge the gates between institution and industries.
We are proud that we have completed the work with the limited time successfully. The AUTOMATIC PNEUMATIC BRAKING AND BUMPER SYSTEM is working with satisfactory conditions. We are able to understand the difficulties in maintaining the tolerances and also quality. We have done to our ability and skill making maximum use of available facilities.
In conclusion remarks of our project work, let us add a few more lines about our impression project work. Thus we have developed an “AUTOMATIC PNEUMATIC BRAKING AND BUMPER SYSTEM” which helps to know how to achieve low cost automation. The application of pneumatics produces smooth operation. By using more techniques, they can be modified and developed according to the applications.
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BIBLIOGRAPHY ---------------------------------------------------------------------------------
BIBLIOGRAPHY
G.B.S. Narang, “Automobile Engineering”, Khanna Publishers, Delhi, 1991,
1.
pp 671. 2.
William H. Crowse, “Automobile Engineering”.
3.
Donald. L. Anglin, “Automobile Engineering”.
4.
Pneumatic Control System----Stroll & Bernaud, Tata Mc Graw Hill Publications, 1999. Pneumatic System----Majumdhar,
5.
New Age India International (P) Ltd
Publishers, 1997.
Web sites: www. Profc.udec.cl/~gabriel/tutorials.com www.carsdirect.com/features/safetyflatures www.hwysafety.org
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PHOTOGRAPHY --------------------------------------------------------------------------------PHOTOGRAPHY
