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Thursday, 18 July 2013

AUTOMATIC HIGHWAY ANTI-COLLIDING SYSTEM






  

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.

Description: Drawing1

·        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
 
                                                              
Output stage
 
-20V
 
+20V
 
                
Signal processing stage
 
High voltage regulator
 
*     
            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.




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