AUTOMATIC HIGHWAY
ANTI-COLLIDING SYSTEM
moses dhilip kumar
SYNOPSIS:
·
Abstract
·
Introduction
·
Working
principle
·
Construction
details
Þ
Ultrasonic
sensor
Þ
Relay
Þ
Non Inverting amplifier
Þ
DC motor
Þ
Solenoid
·
Working
·
Advantages
·
Conclusion
·
References
ABSTRACT:
We are living in an
automobile society, and as far as this field is concerned the accidents are the
main problems that have to be solved. In Chennai alone nearly 1900 fatal road
accidents have taken place in 2005 which nearly claimed 1800 precious lives.
Driver’s assistance system plays a major role in cars since it minimizes
the risk and consequences of accidents and increases the driving comfort level.
Highway anti-colliding system is intended to provide drivers with brake
assistance to avoid front end collision. On highways, if the principle other
vehicle (POV) suddenly stops, then the host vehicle will collide it resulting
in an accident. Due to less reaction time and loss of presence of mind, driver
can’t stop the vehicle through brake.
The aim of this paper is to stop the vehicle
at such circumstances and this paper gives an outline of whole system and
constructional features of each component and working principle. Adaptations of
the system in the future automobiles have also been considered.
INTRODUCTION:
Most of the
collisions take place between the rear of the principle other vehicle (POV) and
the front of the host vehicle due to sudden stoppage of the POV and also this
occurs when a vehicle is parked in the highways during night times which is not
being recognized by the driver. We are
going to sense the stoppage of the POV (Principle other vehicle) using an
ultrasonic sensor. Any vehicle that
reaches a critical distance (6-10m) towards the obstacle is necessary to be
stopped and for this an actuating signal should be given to the relay and the
solenoid. The sensor output voltage will actuate the brake shoes through
solenoid and cuts the drive from the prime mover.
This automotive
collision avoidance has been developed in the centre for Automotive Research
& Training, Department of Automobile engineering in MIT Campus, Anna
University. The model on which the system is tested is made up of wooden
chassis and a sheet metal body. A permanent magnet series motor is used to drive
the vehicle. The current to the DC motor can be reversed to provide for a
braking effort.
WORKING PRINCIPLE:
·
The principle of ultrasonic detection is based on
measuring the time taken between transmission of an ultrasonic wave (pressure
wave) and reception of its echo (return of transmitted wave). The distance
range is 6-10 m.
·
The relay opens or closes its switch contacts in
some prearranged and fixed combination. The contacts may be in the same circuit
or a combination of circuit or in another circuit.
·
When a current is passed through the solenoid the
slug is attracted towards the centre of the coil with a force determined by the
current in the coil. The motion of the slug may be opposed by a spring to
produce a displacement output, or the slug may simply free to move.
·
Torque is produced by interaction between the
axial current carrying rotor conductors and the magnetic flux produced by the
permanent magnets. The only way to control its speed is to vary the armature
voltage with the help of an armature rheostat.
CONSTRUCTION DETAILS:
ULTRASONIC SENSORS:
Ultrasonic sensors have an acoustic
transducer which is vibrating at ultrasonic frequencies. The pulses are emitted
in a cone-shaped beam and aimed at a target object. Pulses reflected by the
target to the sensor are detected as echoes.
The device measures the time delay between each emitted and echo pulse
to accurately deter-mine the sensor-to-target distance.
All materials sensing
Ultrasonic Position Sensors solve the toughest sensing problems and detect
targets made of virtually any material, regardless of color. They detect clear,
transparent and shiny targets as easily as dark and opaque materials. This
ability allows ultrasonic sensors to detect materials ranging from clear glass bottles
to black rubber tires. In a shrink
wrapping operation, for instance, the sensor can accurately and repeatedly
detect the wrapping material regard-less of how shiny or clear it may be.
Ultrasonic sensors also work well in tough environments — fumes, dust, noisy.
Ultrasonic sensors are of the cylindrical type and they
comprise of,
1. High voltage generator
2 .piezoelectric
transducer (transmitter and receiver)
3 .signal
processing stage
4. Output stage
Piezo
electric
transducer
|
|
Excited by the high voltage
generator, the transducer (transmitter-receiver) generates a pulsed ultrasonic wave (200
to 500 kHz depending on the product) which travels through the ambient air at
the speed of sound. When the wave strikes an object, it reflects (echo) and
travels back towards the transducer. A micro controller analyses the signal received and
measures the time interval between the transmitted signal and the echo. By
comparison with the preset or learnt times, it determines and controls the output
states.
The output stage controls a
solid-state double switch (PNP and NPN transistor) corresponding to a NO
contact (detection of object).
Input Voltage : 10-30
V (DC).
Range
: 6-10 m.
Output Voltage: Analog,
0-10 V, 4-20 mA (PNP dual)
RELAY:
A relay is a device which functions
as an electrically operated switch. In response to an electrical, known as
control signal, the relay opens or closes its switch contacts in some
prearranged and fixed combination. Dimension of the relay is about 95* 53*95
mm. The contacts may be in the same circuit or a combination of circuit or in
another circuit. Supply voltage is about 15 volt.
NON INVERTING
AMPLIFIER:
Vo = {1+ Rf/Ri}*Vi.
Rf and Ri is selected so
as to give a gain of 1.4. We need the output voltage of 15 volt. The input
voltage is 10 volts from the sensor. Rf and Ri is selected as 1.4 and 1 kilo
ohms.
DC MOTOR:
A permanent magnet dc (PMDC) motor is similar
to an ordinary dc shunt motor except that its field is provided by permanent
magnets instead of salient pole wound field structure. Ceramite ferrite magnets
are used here. Low voltage PMDC motors produce less air noise and very little
radio noise.
Torque is produced by
interaction between the axial current carrying rotor conductors and the
magnetic flux produced by the permanent magnets. The only way to control its
speed is to vary the armature voltage with the help of an armature rheostat.
Since magnets are permanent magnet, these are totally enclosed to prevent from
magnetic junk.
SPECIFICATIONS
OF PMDC MOTOR:
|
Torque
|
22 kg-m
|
|
Power
|
80 W
|
|
Speed
|
375 rpm
|
|
Voltage
|
24 V
|
|
Current
|
4.5 A
|
SOLENOID:
A solenoid consists of an
electrical coil and a ferromagnetic slug which can move into or out of the
coil. When a current is passed through the solenoid the slug is attracted
towards the centre of the coil with a force determined by the current in the coil.
The motion of the slug may be opposed by a spring to produce a displacement
output, or the slug may simply free so that when the device is energized, it
moves in one direction until it reaches an end to move.
Most solenoids are linear devices,
the electric current producing a linear displacement. They will give a
continuous analog output or with a simple on/off input. The device is generally
arranged when reenergized, a return spring forces it to the other end of its
range of travel where it again reaches an end.
WORKING:
When the POV stops suddenly
and if is within 6-10 m in front of our vehicle, the ultrasonic sensor will
sense the reflected ultrasonic waves from the POV and generates an output
voltage of 10 volts. This is given as input to a non inverting amplifier of Rf
1.5 kilo ohms and Ri 1 kilo ohms.
The output from the non inverting amplifier is 15 volts. This voltage is
given as an input to a relay of 15 volts which is normally closed. The relay is
normally closed with the DC motor circuit. Now the relay switch is opened
thereby it cuts the DC motor drive. Due to inertial motion, the wheel tends to
move in the forward direction. Using the same output voltage from the non
inverting amplifier, the solenoid is actuated which presses the brake shoe
against the wheel thereby stopping of the vehicle occur. Thus collision with
the POV is avoided using our system. The following should also be incorporated
with this system so as to avoid collision with our vehicle.
ADVANTAGES:
Ø Front End
Collision is completely eliminated.
Ø The components
used are easily available and construction is very simple; hence it a low cost
technology.
Ø Practical
implementation of the system is easy and necessary modifications are carried
out for effective performance.
Ø Highly
preferable at night hours during which most drivers feel fatigue.
LIMITATIONS:
While overtaking the forward vehicles, a
certain distance should be maintained between the vehicles otherwise it leads
to unnecessary braking of the vehicle. But this problem can be overcome by
using a microcontroller in the system which analyses the signal and then only
actuate the system.
CONCLUSION:
National
Highway Traffic Safety Administration (NHTSA) estimates that most of the
accidents involving forward end collision are due to the driver’s inattention
or by vehicles following too closely and also it suggests a relatively simple
technology needed for detection and prevention. Most of the accidents are
forward collided. Thus by sensing the sudden stoppage of POV within the certain
range in front of our vehicle, our brake system is actuated so as to avoid
collision. The system can be further developed by using microcontrollers to
analyze the signal. Thus this system is a safety system used in highways so as
to avoid tail to head collision.
.
THANK YOU ALL STAY WITH US 
