AUTOMATIC DISTANCE MEASURMENT AND BRAKING

SYSTEM USING ULTRASONIC SENSOR

SYNOPSIS

Until well into the twentieth century, most devices developed for measuring

distance worked on the same principle. The measured distance is compared with a

standard unit of length. Other means are available. One of these is the measurement of

time taken by the sound wave to cover a certain distance. This sound normally lies

beyond human hearing. The ultrasonic sensor is used to measure the distance in digital

form and also automatically braking the vehicle when the obstacle closer to the vehicle.

The aim is to design and develop a control system based an

intelligent electronically controlled automotive braking system is called

“AUTOMATIC BRAKING SYSTEM”. This Braking system is consists of

ultrasonic sensor unit, IR sensor unit, Pneumatic breaking system. The Ultrasonic sensor

is used to detect the obstacle distance in LCD display. There is any obstacle in the path,

the IR sensor senses the obstacle and giving the control signal to the breaking system.

The pneumatic breaking system is used to break the system.

In our project of ‘ULTRASONIC DISTANCE METER” is suitable for

measuring distances between 25 cm and about 6 m. The measured distance is shown on a

3-digit liquid crystal display (LCD).

The low current drawn by the unit makes battery operation possible: ‘LO BAT’

reading on the LCD indicates when the battery needs to be replaced. The block diagram

of this meter is shown in figurer. This is having the four major parts of the meter

A sender and A Receiver

Timing and time reference section

A counter with display

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.

INTRODUCTION

We have pleasure in introducing our new project “AUTOMATIC DISTANCE

MEASUREMENT AND BRAKING SYSTEM USING ULTRASONIC”, which is

fully equipped by ultrasonic and IR sensors circuit and Pneumatic breaking 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.

The “PNEUMATIC BRAKEING CIRCUIT” can stop the vehicle within 2 to 3

seconds running at a speed of 50 KM. The pneumatic breaking system is a fully

automation project.

This is an era of automation where it is broadly defined as replacement of manual

effort by mechanical power in all degrees of automation. The operation remains an

essential part of the system although with changing demands on physical input as the

degree of mechanization is increased.

Degrees of automation are of two types, viz.

Full automation.

Semi automation.

In semi automation a combination of manual effort and mechanical power is

required whereas in full automation human participation is very negligible.

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.

To reduce man power

To increase the efficiency of the vehicle

To reduce the work load

To reduce the fatigue of workers

To achieve good product quality

Less Maintenance

To reduce the accident 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.

1. ULTRASONIC SENSOR:-

In comparison to X-Rays, ultrasonic encompasses a region where the frequency is

much lower. Ultrasonics or supersonics implies a range of frequencies above the audible

range. We, the human beings can listen to frequencies in the range between 20Hz to

20,000 Hz. Ultrasonics can currently be produced for frequencies as high as 10⁹ Hz.

Ultrasound is widely used in industry and as an important tool in the medical field.

Ultrasonics can be prepared by,

The magnetostriction effect

The piezoelectric effect.

1. MAGNETOSTRICTION EFFECT:

The magnetostriction effect is the phenomenon of expansion or contraction

which takes place in a rod of ferromagnetic material (such as iron or nickel) when placed

in a magnetic field parallel to its axis. The change in the length is a function of the

magnitude of the field and nature of the material.

It is independent of the sign of the field. If the applied magnetic field is

alternating in nature then the rod or tube placed in the field will contract and expand

alternately with the frequency which is twice the frequency of the applied magnetic field.

The longitudinal expansions and contractions produce ultrasonic frequencies. The

frequency of vibration is a function of the dimensions of the magnetostrictive material

and the mode of vibration.

The figure shows an iron bar which is clamped at the middle and placed inside

two coaxial coils. By suitable choice of the value of the condenser C, high frequency

oscillation currents are set up in the circuit coil A. The high frequency current flowing in

coil results in a periodically varying magnetic field this produces alternate compression

and extension of the bar. An induced e.m.f. is now set up in coil B due to the alternate

compression and extension of the bar (inverse magnetostrictive effect).

The induced e.m.f. in coil B now amplifies it producing a higher value of

current in coil A. This in turn produces a higher e.m.f. in coil B (inverse magnetostrictive

effect) thus reinforcing it. In this way, the coil A current ultimately rises to very large

amplitude with a frequency limited by the longitudinal frequency of the rod. If the

frequency of the circuit equals the frequency of vibration of the rod, then resonance takes

place and sound waves of maximum amplitude are produced, by varying the length of the

rod and the capacitance, the frequency can be varied.

Piezoelectric Effect:

By the term piezoelectric effect, we mean production of a potential difference

across the opposite faces of a substance, crystalline or ceramic, due to contraction or

expansion between the opposite faces. This voltage appears due to the crystal lattice

deformation. The application of force to a crystal of quartz or Rochellesalt produces a

voltage across the crystal. Conversely, application of an electric field may cause the

crystal or expand or contract in certain directions. The piezoelectric deformations are

directly proportional to the electric field and changes sign when the field is reversed.

Piezoelectric effect is possible only in crystals that do not posses a centre of symmetry.

Detection of Ultrasonics:

Ultrasonic signals can be detected by thermal detectors, Kundts tube etc. A quartz

crystal may also be used for detection of ultrasound. Electric charges will then be

produced on the pair of faces that are perpendicular to the faces that catches the

Ultrasonics.

Characteristics of Ultrasonics:

The important characteristics of ultrasonic signals are that

(i) Ultrasonic signals exhibit very negligible diffraction due to their small λ

values. They can thus be transmitted over long distances without appreciable

attenuation or loss.

(ii) The speed of propagation of ultrasonic signals depends on their frequency, i.e.

the speed decreases with decrease of frequency.

(iii) Ultrasound is highly energetic.

(iv) If an ultrasonic wave is transmitted through a liquid, stationary wave patterns

are generated due to the reflection of the wave from the other end. The liquid

density thus changes from layer to layer along the propagation direction. A

plane diffraction grating can thus be formed which can diffract light.

(v) Intense ultrasonic wave possesses a disruptive effect in some fluids.

Applications of Ultrasonics:

The applications of Ultrasonics are too many. Some of the applications of

Ultrasonics are,

(i) Physical, chemical and biological effects

(ii) Ultrasonic flaw detection

(iii) Depth sounding (or sound signaling)

(iv) Cleaning and clearing

(v) Direction signaling

(vi) Coagulation and crystallization

(vii) Degassing of liquids by ultrasonic waves

(viii) Metallurgical applications

Ultrasonic in medicine.

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) ULTRASONIC SENSOR UNIT

5) WHEEL AND BRAKE ARRANGEMENT

6) PU CONNECTOR, REDUCER, HOSE COLLAR

7) STAND

8) SINGLE PHASE INDUCTION MOTOR WITH PULLEY

SOLENOID VALVE (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 intelligent control unit.

In our project cut of solenoid valve is used for flow direction of braking cylinder.

It is used to flow the air from air tank to the single acting cylinder.

Single acting cylinder

Single acting cylinder is only capable of performing an operating medium in only one

direction. Single acting cylinders equipped with one inlet for the operating air pressure, can

be production in several fundamentally different designs. Single cylinders develop power in

one direction only.

Therefore no heavy control equipment should be attached to them, which requires to be

moved on the piston return stoke single action cylinder requires only about half the air

volume consumed by a double acting for one operating cycle.

APPLICATIONS AND ADVANTAGES

APPLICATION:

For automobile application

Industrial application

ADVANTAGES

Brake cost will be less.

Free from wear adjustment.

Less power consumption

Less skill technicians is sufficient to operate.

It gives simplified very operation.

Installation is simplified very much.

To avoid other burnable interactions viz.… (Diaphragm) is not used.

Less time and more profit.

SPECIFICATION

1. Single acting pneumatic cylinder

Technical Data

Stroke length : Cylinder stoker length 170 mm

Quantity : 2

Seals : Nitride (Buna-N) Elastomer

End cones : Cast iron

Piston : EN – 8

Media : Air

Temperature : 0-80 º C

Pressure Range : 8 N/m²

2. 3/2 solenoid valve:-

Technical Data:

Size : ¼”

Pressure : 0 to 8 kg / cm2

Media : Air

Type : 3/2

Applied Voltage : 230V A.C

Frequency : 50 Hz

3. Flow control Valve

Technical Data

Port size : 0.635 x 10 ֿ² m

Pressure : 0-8 x 10 ⁵ N/m²

Media : Air

Quantity : 1

4. Connectors

Technical data

Max working pressure : 10 x 10 ⁵ N/m²

Temperature : 0-100 º C

Fluid media : Air

Material : Brass

5. Hoses

Technical date

Max pressure : 10 x 10 ⁵ N/m²

Outer diameter : 6 mm = 6 x 10 ˉ ³m

Inner diameter : 3.5 mm = 3.5 x 10 ˉ ³m

IMPORTANT FEATURES

Distance measurement upto 6 meter

Fast pick-up

Low maintenance expenditure

Good efficiency

LCD is used to measure the distance in meter..

Microcontroller IC 89C51 has large memory capacities.

Simple, easy to construct.

Battery low indication is provided in the LCD display for weak battery replacement

Distance is measured by simply pressing the bush button continuously.

BLOCK DIAGRAM

POWER SUPPLY

CONTROL

UNIT

ULTRASONIC TRANSMITTER

PNEUMATIC CYLINDER

SOLINOID VALVE

BRAKE ANGEMENT

ULTRASONIC RECEIVER

FLOW CONTROL VANVE

AIR TANK(COMPRESSOR)

INTERNAL BLOCK DIAGRAM OF ULTRASONIC DISTANCE METER:-

APPLICATIONS

It is used to measure the distance between two blocks (bellow 6 meter).

Depth measurement.

Length Measurement.

Height Measurement.

Automobile Application

CLK ECOUNTER

CENTRALTIMING

CLOCK17.05 kHz

SENDER

RECEIVER

S R

BISTABLE

LCD DISPLAY

DISADVANTAGES

This circuit only measures the distance bellow 6 meter.

This circuit doesn’t senses fast moving obstacle distance.

Cost of the sensor is very high when compared to other sensors.