18-04-2011, 02:41 PM
Submitted by
DHINESH NS
VELMURUGAN P
VENKATARAMANAN S
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ABSTRACT
Our Project proposes a vehicle-to-vehicle communication protocol for cooperative collision warning. Emerging wireless technologies for vehicle-to-vehicle (V2V) communications are promising to dramatically reduce the number of fatal roadway accidents by providing early warnings. One major technical challenge addressed in this our project is to achieve low-latency in delivering emergency warnings in various road situations. Based on a careful analysis of application requirements, we design an effective protocol, comprising congestion control policies, service differentiation mechanisms and methods for emergency warning dissemination. Simulation results demonstrate that the proposed protocol achieves low latency in delivering emergency warnings and efficient bandwidth usage in stressful road scenarios. The wireless data communication between two vehicles is provided by introducing Zigbee technology. It is designed around low-power consumption allowing batteries to essentially last forever. The distance measurement is provided by Ultrasonic sensors. Ultra sonic sensors are transmitting and receiving ultrasonic signals
CHAPTER 1
INTRODUCTION
Road accidents account for a severe threat to human lives from both an injury as well as a financial perspective. Given that vehicles are designed to facilitate a smooth means of transportation, manufacturers have long been in the process of designing vehicles based on principles of reliability and safety. However, due to reasons such as human-error, circumstantial error and negligence, accidents occur. Today, special attention is focused on the technologies that can reduce traffic accidents. V2V technologies are simple to implement primarily because of their reliance on wireless communication.
The communication protocol includes Zigbee to communicate the information between two vehicles. The distance measurement between two vehicles is done by Ultrasonic sensor. The microcontroller controls entire process, it is programmed to send a signal to buzzer and zigbee when the distance range is obtained. The main objective of our project is to alert the driver when he closes to the front vehicle. During night times some of the vehicles such as car, bus may break down at the highways. This vehicle now appears to be an obstacle to the vehicle that is coming behind of it. This causes a greater chances of accident, the vehicle coming behind may hit hardly to the back of stationary vehicle and it may lead to the greater damage.
CHAPTER 3
ULTRASONIC SENSOR
3.1 FUNCTION:
They are also known as transducers, they both send and receive the signal. It works on the principle similar to radar or Sonar which evaluate attributes of a target by interpreting the echoes from radio or sound waves respectively. They generate high frequency sound waves and evaluate the echo which is received back by the sensor. Sensors calculate the time interval between sending the signal and receiving the echo to determine the distance to an object.
Whenever a sound wave moving in air hits a solid surface it reflects . We often call this reflected sound as an echo. The same applies to a sound wave moving through water and hitting an obstacle. If we know the speed of sound in the air or water we can calculate the distance. To perform this we must measure the time taken for a pulse of sound to travel to the object and back again. The distance to the object and back is given by (distance=Speed * Time). As this is the total distance that the sound has traveled to the object and back, we must divide by 2 to find the one-way distance. This use of echoes is the basis of SONAR. The pulse of sound that is used should be short and high frequencies are usually used as they travel further without being absorbed. Sounds with a frequency above 20 kHz are called ultrasonic(beyond the range of human hearing). The speed of sound varies from one material to another. Typical speeds are approximately 330 m/s in air, 1500 m/s in water, 5000 m/s in a metal. Here the ultrasonic sensor calculates the distance between the sensor and the obstacle and transmits it to the system. Once an object is detected, a signal is sent to the onboard sense and avoids collision and corrective action is taken by the use of micro-controller.
DISTANCE MEASUREMENT:
Different techniques can be used to measure the distance by using ultrasonic sensors. Among them , continuous-wave and pulse-echo technique are widely known. In continuous-wave methods, the transmitter generates a continuous output, whose echo is detected by a separate receiver. In this case, accuracy depends on the measurement of the phase shift between the transmitted and the reflected wave. Although better performance than with pulse-echo measurements can be obtained, complex hardware is required to measure the phase, and in most cases, different frequencies need to be used to determine the number of integer wavelengths in the phase shift.
Pulse-echo techniques are widely used in commercial systems due to less complexity of hardware. In pulse-echo technique, a short train of pulses is generated, enabling the same transducer to be used both as a transmitter and as a receiver. In the measurement methods, based on pulse-echo, the distance information is retrieved from a time-offlight measurement, i.e., the time an ultrasonic wave needs to travel from the transmitter to the receiver after being reflected by an object. The pulse-echo technique is used in this paper to calculate the distance of the obstacle from the vehicle. The distance between the transmitter and the object is determined using the following equation:
D= (t * c) / 2
Where D- Distance between the source and the obstacle
c- Ultrasonic wave velocity in air
t- Time interval between pulse emission and echo detection.
CHAPTER 4
MICROCONTROLLER AT89C51
4.1 FEATURES:
1. Compatible with MCS-51™ Products
2. 4K Bytes of In-System Reprogrammable Flash Memory– Endurance: 1,000 Write/Erase Cycles
3. Fully Static Operation: 0 Hz to 24 MHz.
4. Three-level Program Memory Lock
5. 128 x 8-bit Internal RAM
6. 32 Programmable I/O Lines
7. Two 16-bit Timer/Counters
8. Six Interrupt Sources
9. Programmable Serial Channel
10. Low-power Idle and Power-down Modes
4.2 DESCRIPTION:
The AT89C51 is a low-power, high-performance CMOS 8-bit microcomputer with 4K bytes of Flash programmable and erasable read only memory (PEROM). The device is manufactured using Atmel’s high-density nonvolatile memory technology and is compatible with the industry-standard MCS-51 instruction set and pinout. The on-chip Flash allows the program memory to be reprogrammed in-system or by a conventional nonvolatile memory programmer.
