ADAPTIVE TRAFFIC CONTROLLER

trafic signal fyp

The purpose of our final year  project was to design a Traffic system that generates its own power by the movement of vehicles and also by sensing traffic conditions adjusts its timing accordingly.
Its other features include giving preference to emergency vehicles and this system can be controlled manually through our controller. The basic idea is to get a steady flow of traffic going without and hitches and hiccups. Our controller can adjust it time, if there are more cars passing through one side than controller will increase the timing of that side accordingly. We used sensors and specially made pads for sensing the amount of traffic passing through a junction. The system is completely based on FPGA.

 Overview

The main purpose of our project was to eliminate the existing problems in traffic control structure and also add to it some features of our own. Our controller uses different sensors and controller to control the flow of traffic and also we have added a separate feature that is the detection of emergency vehicles and giving preference to that side of the traffic intersection.

 

 Project Report Organization

Our report will be organized according to the given pattern. There are a total of nine chapters.

This chapter gives a brief overview of our whole project ranging from the objectives to our motivations, and the usage of specific tools to fulfill our objectives.

The second chapter is about literature review. A brief review is provided of all the existing work we studied for the duration of this project.

The third chapter gives a detailed account of the background of traffic lights and the different control methods and detectors that were used to control traffic

The fourth chapter is about the kit we chose for our controller i.e. FPGA Nexys 2. All the important details regarding this kit are provided in this chapter.

The fifth chapter is about the coding of the controller and the achievement of the objectives by programming the controller.

The sixth chapter is about the generation of power for our system, the goals related with it and how it was achieved.

The seventh chapter is all about the smart control of traffic and how it’s done.

The eighth chapter and final chapter covers the results and lists all the conclusions from our project.

 

 Motivation

In recent years, the need for transportation has increased greatly for people in Pakistan, which has led to the rise in number of vehicles in the country. Due to this, traffic jams are very common. This was our inspiration and motivation as we wanted to design a controller that helps reduce traffic jams and waiting times during rush hours and also to produce power for our system from the movement of vehicles.

 

 Objectives

Our aim was to improve on this existing system and something new to it that improves signal timings and let the system adapt to the traffic conditions.

 

The following steps were taken to achieve our required objective:

  • Design of a new traffic controller using Fpga kit Spartan3e. We coded the Fpga kit from ground up to act as a controller of our entire project. All the sensors were interfaced with it.
  • A new module which approves and prefers to give way to an emergency vehicle such as an ambulance or a fire brigade vehicle. For this module we used IR sensors to detect light from the specially mounted IR bulbs on the emergency vehicles.
  • Addition of a module which would provide self-generated power for the signals. Our initial work was done on the piezo-electric sensors but we moved on to specially made pads which used gear motors to generate power.
  • The power generated from these pressure pads will be stored in the batteries so that it provides power for our system when needed.
  • As our system is adaptive, it also gathers data from the pressure pads, the pressure applied on the pads from the movement of the vehicles generate current. More the pressure more the current. By taking the account of current it is first converted into voltage form and then this analog voltage is digitized using ADC 0804 and fed into the FPGA, and then decide whether to change the timing of the signal or not.

All the coding was done on Xilinx using verilog HDL (Hardware Description Language). The code was burned on the Fpga kit using Adept, which comes with the FPGA kit.

Here is a brief summary about the usage of these tools.

 

Xilinx:

We used the Xilinx tool for coding and then testing our code by using built-in RTL schematic diagrams and graphs plotted against the clock to test and re-test our code before burning and implementing on the Fpga. The built-in clock in Spartan-3e is 50 MHz, that gave us very little time to test our program, so we decreased the frequency by coding a clock divider in Xilinx, and cutting the clock frequency to just 3 Hz.

 

Nexys2:

Nexys2 was used as our main controller, once the code was burned onto it, we performed the functions we coded onto it, moving on we interfaced sensors as well as an ADC (analog to digital converter) with it. The clock to the ADC was also provided from it. So, that our whole controller was in sync with all the sensors interfaced with it.

block diagram of fyp

block diagram of fyp

 

 

Detailed description about the project and our work that we have done by using the above described tools will be explained in the following chapters.

 Introduction

The simplest traffic light consists of either a single or a pair of traffic lights that warns the user of any possible danger. To understand how a typical traffic system works take a look at the following figure.

trafic signal

 

 

 

Starting from the first signal (state 1), initially the red light is ON, then after specific intervals, it moves onto yellow light (state 2), then green (state 3) and back to yellow (state 4). This cycle continues in a typical traffic system.

The normal function of traffic light assures that an easy flow of traffic is maintained without any accidents and it also takes the safety of the pedestrians into account.

There are a plethora of different traffic control techniques; some of which are mentioned below

 Fixed Time Control

The old form of traffic controller uses electro-mechanical system to control traffic. They are called electro-mechanical traffic controllers. They mostly consist of movable parts unlike a computerized controller which has sensors and switches. They used dial timers and electrical relays to control the flow of traffic. The dial timers are set to a fixed value for each intersection. The dial timers have cycle gears which control the timing; they basically range from 35 to 120 seconds.

 

 Dynamic Control

Dynamic signals are programmed to change their timings with respect to the changing traffic conditions. These types of systems minimize the delay at an intersection as it can provide more time to the lane with more traffic while keeping the timing for the other systems the same.

These systems usually use detectors to sense traffic conditions, the input from the detectors is fed into the controller, the sensors inform the controller whether there are vehicles are pedestrians present at the road.

A system usually has the following detector types; one or more than one detector can be present and functional in a system at any given time.

 In-pavement (Underground) Detectors:

These are the most common type of detectors. These are buried in the roads and they sense the vehicles present on the road at any given time and thus can reduce the time when a green signal is given to an empty road. Following are the different types of underground traffic detectors.

 

 Induction Loops:

These loops can detect vehicles passing or arriving at a certain area on the road.  For, this purpose an electrically conducting loop in installed in the pavement or under the road.

Inductive loop detectors consist of these loops of wires that are installed in the pavement and these loops are connected to a controller, energy is transmitted into these wire loops at frequencies between 10 kHz to 200 kHz. The inductive-loop system behaves as a electrical circuit in which the loop wire and lead-in cable are the inductive elements. When a vehicle passes over the loop or is stopped within the loop, the inductance in the loop in decreased, which shows the presence of a vehicle to the controller. Thus, this loop helps the controller to sense the passage or presence of vehicles.

 

  Inductive Loop Sensor

The structure of the loop means that only large metal masses will be able to decrease the inductance in the loop. This is also beneficial in a way that a small metal structure will not trigger a false signal but there is also a disadvantage that small vehicles like bicycles and motor bikes will not register on the sensor and thus they can be ignored by the signal.

Advantages:

  1. They are rugged and are best to be used in any weather and any light condition.
  2. It is the most reliable and accurate detector in term of vehicle count.
  3. These detectors have a well defined area of detection i.e. they can cover a large area if the size of the coil is increased.

Disadvantages:

  1. The main let-down of these detectors is that they will detect any thing that is metal. They cannot differentiate between a vehicle and any other object.
  2. These detectors are difficult to install, first of all the traffic has to be blocked or diverted and digging of roads is required to install these detectors. This disrupts the traffic
  3. They cannot measure the speed of a moving vehicle.

 

 Magnetic Detectors:

The magnetic detector is a simple, inexpensive and rugged device that is capable of only a pulse output. It can be used for measuring traffic and controlling the signal according to it or simply to count vehicles. Some magnetic sensors are by boring and digging the roadway. Others are mounted under bridges or in holes cored into the road surface.

 

  Non-intrusive Detectors (Non-pavement Detectors)

These sensors get their name of non-intrusive detectors as they do not disrupt the traffic. They record vehicle count without interruption to the flow of traffic. Installations of non-intrusive detection systems usually have no requirement for road closure or diversion and they are usually deployed onto existing road side infrastructure.

Some of these detector technologies include video image processors, sensors that use electromagnetic waves or acoustic sensors that detect the presence of vehicles at the intersection.

 

These are some of these non-intrusive detectors:

  • Infrared sensors
  • Ultrasonic sensors
  • Microwave vehicle motion sensors
  • Acoustic Sensors

 

 Infrared Detectors:

Infrared sensors are of two types; active and passive. Both can be used to monitor traffic conditions.

 

Active infrared:

These sensors transmit energy of their own. It showers the detection region with low-intensity infrared energy. Some of this transmitted energy is reflected back by the vehicles towards the sensor. These reflected waves are thus detected by the sensors.

 

 

Passive Infrared:

Passive sensors have no energy of their own. They detect energy from two different sources; the energy from the vehicles, roads and other objects, and also the energy from the environment that is reflected by the vehicles, road surface and other objects.

 

View from a passive IR-sensor

 

 Ultrasonic Detectors:

Ultrasonic sensors transmit pressure waves of sound energy ranging between 25 KHz to 50 KHz. They measure the distance that the reflected wave travels, if it is different than the distance to the road surface, they sense the presence of a vehicle.

 Working of an Ultrasonic sensor detector

 Microwave Radars:

Radar is defined as “a device for transmitting electromagnetic signals and receiving echoes from objects of interest (i.e., targets) within its volume of coverage.”

Microwave radars transmit microwave energy toward the surface of the road.

When a vehicle passes through the transmitted beam, a portion of the transmitted energy is reflected back towards the antenna. The energy then enters a receiver where the detection is made and traffic flow data, such as volume, speed, and vehicle length, is calculated. Microwave sensors that transmit a continuous wave (CW) Doppler waveform can only detect vehicle passage and measure vehicle count and speed. They cannot detect stopped vehicles. Microwave sensors that transmit a frequency modulated continuous wave (FMCW) detect vehicle presence as well as vehicle passage.

 

 Working of a Microwave Radar

 

 

 

 

 

 

 Acoustic Sensors:

These sensors detect vehicle presence, passage and speed by detecting sounds produced by the vehicles. When a vehicle passes through the zone an increase in sound energy is detected and vehicle presence signal is generated.

 

 Non-motorized user detection

Non-motorized users are pedestrians and bicyclists. Mostly, these users are detected by demand buttons and detectors. Pedestrians are detected by especially mounted push switches at crossings. While, bicycles are sensed by detectors. Detectors usually can’t detect bicycles because of low metal content, if a bicycle rides directly over the wires of a detector then it might be detected but a detector isn’t always triggered by the presence of a bicycle. Some places simply have additional buttons along with the pedestrian buttons so that cyclists can reach them easily.

Both methods are widely used for the detection of non-motorized vehicles, according to the different needs.

 

 

 

 Coordinated Control

An effort is made usually to coordinate all the traffic signals with each other so that a driver can get a series of green lights. There is a difference between coordinated signals and synchronized signals. Synchronized signals all change at the same time. While, coordinated systems are controlled from a master controller and are set up so that a set of vehicles get series of green lights throughout. Most recently, more advanced coordinated system have been developed which use live feed from each intersection and coordinate the traffic system in real-time.

Advantages:

  • More traffic can pass through the same roads through a coordinated system.
  • Reduction in traffic jams.
  • Less collisions and accidents, as coordinated systems encourage users to travel within the speed limits to get green lights throughout.
  • Improvement (reduction) in journey time.

Disadvantages:

  • Advanced coordinated systems are very costly to implement.

 

 Other types of control

  • In case of a failure, if power is available an amber (yellow) light flashes to warn users of upcoming intersection.
  • Some traffic lights only operate part time. Some lights only work during the day and are off during the night time.
  • Some lights outside emergency stations such as fire brigade have no green, they are usually off, but turn amber and then red in case a fire vehicle is exiting from the station.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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