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INTRODUCTION
Generally a tracking system is used for the observing of persons or objects on the move and
supplying a timely ordered sequence of respective location data to a model, for example
capable to serve for depicting the motion on a display capability. An antenna is a metallic
device for radiating or receiving radio waves, which may just even be a rod or a wire. In other
words an antenna is a transitional structure between free space and a guiding device. Certain
air borne systems are designed for specific applications such as satellites for monitoring the
climate conditions, satellites for telecommunication or for radio and television broadcasting,
unmanned air vehicles for aerial security, aerial photography. Tracking of such systems
becomes a matter of utmost concern due to their highest priority applications [5].
While many methods already exist for tracking of airborne systems, most of these systems
lack portability due to their gigantic size. This system aims at overcoming the extremely high
cost of the existing system, the absence of modularity and portability and also improving the
execution, taking into consideration various parameters. The system finds its application in
various verticals which begin from defence and continue over confidential and specific
frames such as satellites and spaceships. It uses a directional antenna, namely the Yagi-Uda
antenna, which moves in the direction of the airborne system and hence all the power is
supplied into a signal direction. This design achieves a very substantial increase in antenna’s
directionality and the gain compared to a simple dipole.
The system obtains GPS coordinates from the UAV to be tracked and converts them into
required azimuth and elevation values using a predefined code. These values are used to
update the antenna position for every new value of the GPS coordinates. Thus there is a trade
off between the Hardware and the software control.
The purpose of a tracking system is to determine the location or direction of a target on a
near-continuous basis. An ideal tracking system would maintain contact and constantly
update the target's bearing (azimuth)[1], range and elevation. The output of the tracking
system can be sent to a control system, which stores the information and derives the target's
motion and therefore its future position. The tracking systems not only provide an automatic
target following feature but also determine the target's position with sufficient accuracy
The functionality of the tracking system is mentioned as follows
The system is in the ready state initially.
As soon as an airborne system is located in its range of operation, the system starts to
receive its GPS coordinates.
On receiving the GPS coordinates, the azimuth and elevation are decoded.
The software module updates the hardware module in accordance with the decoded
values.
The antenna, which is controlled by the hardware module, follows the air borne
system and collects data from it.
1.1 Definitions and Usage
Yagi-Uda antenna
A Yagi-Uda array, commonly known simply as a Yagi antenna, is a directional[2]
antenna consisting of a driven element (typically a dipole or U-shaped folded dipole) and
additional parasitic elements (usually a so-called reflector and one or more directors). The
reflector element is slightly longer (typically 5% longer) than the driven dipole, whereas the
so-called directors are a little shorter. This design achieves a very substantial increase in the
antenna's directionality and gain compared to a simple dipole.
Highly directional antennas such as the Yagi-Uda are commonly referred to as "beam
antennas" due to their high gain. However, the Yagi-Uda design only achieves this high gain
over a rather narrow bandwidth, making it useful for specific communications
bands. Amateur radio operators ("hams") frequently employ these on HF, VHF,
and UHF bands, often constructing antennas themselves ("home brewing"), leading to a
quantity of technical papers and design software. Yagis are not very useful for signals spread
across a wide band, like television signals, where the similar looking log-periodic dipole
array is commonly used, which works on different principles.
Global Positioning System (GPS)
The Global Positioning System (GPS) is a space-based satellite navigation system that
provides location and time information in all weather conditions, anywhere on or near the
Earth where there is an unobstructed line of sight to four or more GPS satellites. The system
provides critical capabilities to military, civil and commercial users around the world. It is
maintained by the United States government and is freely accessible to anyone with a GPS
receiver. A GPS receiver calculates its position by precisely timing the signals sent by
GPS satellites located high above the Earth. Each satellite continually transmits messages that
include
The time the message was transmitted and,
Satellite position at time of message transmission.
Microcontroller
A microcontroller (sometimes abbreviated µC, uC or MCU) is a small computer on a
single integrated circuit. It contains a processor core, memory, and input/output peripherals
which are programmable in nature.
Microcontrollers are used in automatically controlled products and devices, such as
automobile engine control systems, implantable medical devices, remote controls, office
machines, appliances, power tools, toys and other embedded systems. By reducing the size
and cost compared to a design that uses a separate microprocessor, memory, and input/output
devices, microcontrollers make it economical to digitally control even more devices and
processes. The following are some of the important features of microcontroller are
It has a dedicated CPU
The memory is inbuilt.
It is a computer on a Chip.
There are more instructions which are bit addressable.
I/O ports are present on the chip itself.
Servo and Stepper motor
The basic difference between a traditional stepper and a servo-based system is the type of
motor and how it is controlled. Steppers typically use 50 to 100 pole brushless motors while
typical servo motors have only 4 to 12 poles. A pole is an area of a motor where a North or
South magnetic pole is generated either by a permanent magnet or by passing current through
the coils of a winding. Steppers don't require encoders since they can accurately move
between their many poles whereas servos, with few poles, require an encoder to keep track of
their position. Steppers simply move incrementally using pulses (open loop) while servo's
read the difference between the motors encoder and the commanded position (closed loop),
and adjust the current required to move.
Aim
“Design and development of an Antenna Tracking System for Airborne
vehicles in UHF communication range”
1.3 Objective
The purpose of this project is to develop an Antenna Tracking system for UHF
communication signals, so as to reduce human involvement and help track exact position of a
system under consideration, which may vary from an unmanned air vehicle to an unmanned
ground vehicle or even a satellite.
1.4 Problem Statement
Tracking has become a concern of utmost importance due to loss of various airborne systems
during their flight time. Hence a system for tracking the airborne vehicles position at all times
is a necessity. Antenna Tracking has its own setbacks at due to faults in Antenna design and
GPS inaccuracy. This project aims at developing an accurate tracking system by following
the airborne system continuously.
1.5 Scope
This project is developed in order to help the Indian Space Research Organisation (ISRO) in
making its present working system a better one by eliminating the loopholes present in it.
Based on the responses and results obtained as a result of significant development in the
working system of ISRO, this project can be further extended to meet the demands according
to situation. This can be further implemented to have control room to regulate the working of
the system and hence it becomes user friendly. The hardware can be expanded and used in
a station with any number of platforms as per the usage. Additional modules can be added
without affecting the remaining modules. This allows the flexibility and easy maintenance of
the developed system. There is no lag time to operate the device and it offers high accuracy.
This project will discuss on
Background of Yagi-Uda antennas.
Parameters involved in the alignment and tracking system of the antenna
Control system design for alignment and tracking system.
Implementation of the parameters involved in tracking system.
1.6 Motivation
In the mid-1960s, the commercial satellite communications industry has started and in less
than 50 years, has progressed from an alternative technology to mainstream transmission
technology. Today’s communication satellites offer extensive capabilities in applications
involving data, voice and video, with services provided to fixed, broadcast, mobile, personal
communications and private network users.
Space research and development is one of the fastest growing areas of technology, hence the
reason for development of this prototype is majorly influenced by the extremely “high cost of
the existing technology” and also by the ever growing existence of UAVs (Unmanned Air
vehicles) and MAVs (Micro air vehicles). Tracking of UAVs and MAVs is becoming a
concern of utmost importance. Some of the other important reasons for going ahead with the
idea of development of an antenna tracking system is because it can deal all RFs (Radio
frequencies), along with its modularity and portability. Such a system finds a wide variety of
applications in the defence sector.
1.7 Methods Available for Airborne Tracking
Following are the methods available for tracking of airborne systems
1. RADAR - It is also known as Radio Detection and Ranging. This method of detection
is most often used in commercial flights and defence aircrafts. Such systems consist
of Transponders for transmission and reception. The tracking is done by sending a
signal to the RADAR installed on the flight - This is called transmission and a signal
is sent back to the base station This is termed as reception. The complete process is
known as transpondance. For example - The transponders of the Malaysian Aircraft
MH370A were switched off by accident which lead to the failure in tracking of the
flight and flight is missing ever since.
2. GPS - It is also known as Global Positioning System. This method is most often used
in satellite and UAV tracking. The airborne systems consist of a GPS module on
board, which sends out coordinates constantly at a particular frequency, which are
received with the help of a receiver antenna. These values are converted into
appropriate linear values in order to decode the position location. Basic GPS
measurements yield only a position, and neither speed nor direction. However, most
GPS units can automatically derive velocity and direction of movement from two or
more position measurements. The disadvantage of this principle is that changes in
speed or direction can only be computed with a delay, and that derived direction
becomes inaccurate when the distance travelled between two position measurements
drops below or near the random error of position measurement. In typical GPS
operation, four or more satellites must be visible to obtain an accurate result
1.8 Constraints
For proper operation of this model when it is implemented, certain precautions must be taken
due to its constraints.
It is extremely hard to design a proper working model of Yagi-Uda antennas. This is
not a simple task as it involves many equations, simulations and testing phases.
Continuous flawless tracking is a huge challenge experienced in tracking systems.
The airborne systems under consideration might be very fast when compared to the
speed of operation of the tracking system.
Positive stability of the system is a matter of concern. As long as the system is
positively stable, the tracking can occur and the antenna is oriented in the direction of
the airborne system.
1.9 Sections of the Report
In this project, an antenna tracking system for airborne vehicles is devised. The various
surveys and experiments done during the timeline of the project are explained in detail.
Chapter 1 gives a brief introduction to the project, its purpose, scope, motivation and
definitions of some of the terms involved.
Chapter 2 shows the survey done in the existing literary works which were used in building
modules for AURORA.
Chapter 3 briefs the theoretical background required to design the antenna and control
system.
Chapter 4 mentions the requirements in hardware and software and their specifications
Chapter 5 explains the detailed design and the methods used to implement AURORA
Chapter 6 shows of the analyses done on the antenna and control system. It also shows the
observations done while experimenting on a quadcopter.
Chapter 7 gives the inference and concludes the report.
LITERATURE SURVEY
Many papers were referred during the design and construction of AURORA. The survey
made are mentioned below.
2.1 Survey of Literary Works
1. Seitz J, Vaupel T, Thielecke J, Published in: Information Fusion (FUSION), 2013
16th International Conference. Page(s) 1479 – 1486, Date of Conference 9-12 July
2013.[1]
Purpose - Tracking algorithms for estimating and tracking the azimuth angle of
position of a mobile unit carried by a pedestrian are presented. Signal strengths
measurements are collected using directional antennas. Azimuth can be tracked.
Outcome - Measurements have been collected inside and outside of an office
building to evaluate the performance of the different tracking algorithms.
2. Zhefeng Sun, Huan Li, Published in: Distributed Computing Systems Workshops
(ICDCSW), 2013 IEEE 33rd International Conference. Page(s) 274 – 279, Date of
Conference 8-11 July 2013.[2]
Purpose - Most existing work concentrates on improving the accuracy and energy
saving in a fully covered area by making full use of omni-directional antenna. Due
to the death of sensors caused by harsh environment or energy depletion.
Outcome - Simulation results have shown that the proposed approach can realize
the real- time detection of moving object when it runs into and out of the hole, and
consume much less energy than the omnidirectional antenna based methods.
3. Tserenlkham B, Batdalai S, Published in: Strategic Technology (IFOST), 2013 8th
International Forum(Volume 2 ), Page(s) 159 – 162, Date of Conference June 28
2013-July 1 2013.[3]
Purpose - The portable terminals need tracking mechanisms to allow
quick deployment. The accurate tracking is important to maintain the Eb/No.
Outcome - The application of intelligent control algorithms would be
considered to cover areas such as orbit determination, optimal estimation
techniques, performance, and practical implementation etc.
Zhong-Ke Shi, Published in: Machine Learning and Cybernetics, 2013. Proceedings.
2013 International Conference , 900 – 905, Date of Conference 2013.[4]
Purpose - A conception of real-time iterative learning control is first
introduced. PID learning control algorithm for nonlinear systems is presented.
Outcome - The new approach can be used in online control. The results of
application to AC servo motor control show that this method is highly robust
to model changes.
5. T. He, C. Huang, B. Lum, J. Stankovic, and T.Adelzaher, in Proc. ACM MobiCom,
San Diego, CA, pp. 81–95, Sept. 2003.[5]
Purpose - Most applications of wireless sensor networks require that
the sensor nodes be location-aware. The authors designed a novel range-free,
neighbour-information-based localization system (NBLS) which takes
neighbour information into account besides hop information used in DV-Hop.
Outcome - A Likelihood-Based location estimator is proposed here and is
bounded by an uncertainty region which is helpful to localize other sensors of
the network.
2.2 Research Gap:
The antenna tracking systems and their modules presented the various papers demonstrate
many techniques of tracking. The advantage is the existence of flawless tracking. The
satellites and airborne systems are tracked with great precision and high accuracy. The
systems existing show better performance.
But the main defect in the existing systems is their high cost. The systems are not portable.
They are bulky and large in size. They have all the modules in the existing systems are
integrated in such a way that they can’t be separated and re-integrated.
The very fact that these systems are expensive and bulky make them difficult and complex to
use. Hence a system is designed in such a way that it can be easily modified and transported.
The cost of the new designed system is so less that it is practically feasible to construct it and
use it anywhere. The system is made to be very inexpensive.