IJECET Data Acquisition and Telemetry for UAVs

International Journal of Electronics and JOURNALEngineering & Technology (IJECET), ISSN 0976 –
INTERNATIONAL Communication OF ELECTRONICS AND
6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 5, September – October (2013), © IAEME

COMMUNICATION ENGINEERING & TECHNOLOGY (IJECET)

ISSN 0976 – 6464(Print)
ISSN 0976 – 6472(Online)
Volume 4, Issue 5, September – October, 2013, pp. 90-100
© IAEME: www.iaeme.com/ijecet.asp
Journal Impact Factor (2013): 5.8896 (Calculated by GISI)
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IJECET
©IAEME

DATA ACQUISITION SYSTEM AND TELEMETRY SYSTEM FOR
UNMANNED AERIAL VEHICLES FOR SAE AERO DESIGN SERIES
Ramesh Kamath1, Siddhesh Nadkarni2, Kundan Srivastav3, Dr. Deepak Vishnu Bhoir4
1,2,3

UG Students, Department of Electronics Engineering,
Professor and Head, Department of Electronics Engineering
Fr. Conceicao Rodrigues College of Engineering
Fr Agnel Ashram, Bandstand, Bandra (W), Mumbai, Maharashtra, India. Pin Code: 400 050
4

ABSTRACT
Society of Automotive Engineers (SAE) conducts ‘Aero Design Series’ competition annually
in the United States of America (USA). This paper explains and details about a ‘Data Acquisition
System (DAS)’ and a wireless Telemetry system which is the requirement for the Unmanned Aerial
Vehicles (UAVs) of 'Advanced class' of this competition. The major requirements that DAS and
Telemetry systems on UAVs must fulfil are: long range, low power consumption, accuracy of
measurements and compact size. In order to fulfil these requirements, our system comprised of an
altimeter, Global Positioning System (GPS) module, microcontroller, ZigBee modules and a display
unit for GUI at the base station. The system performed well and stood true on all its expectations.
There are off-the-shelf solutions available for the task but they lack on one parameter or other.
Additionally, their cost is prohibitive at times. The system, explained in this paper, is comprehensive,
inexpensive and rugged and can be implemented on any kind of UAV operation such as surveillance,
weather forecasting, amateur UAVs, and other related applications.
Keywords: Aero, Altimeter, Arduino, DAS, GPS, SAE, Telemetry, UAV, XBee, ZigBee
I.

INTRODUCTION

SAE International is a global association of more than 138,000 engineers and related
technical experts in the aerospace, automotive and commercial-vehicle industries. SAE
International's core competencies are life-long learning and voluntary consensus standards
development. To nurture and encourage talent in the field of aviation, SAE International conducts
‘Aero Design Series’ competition annually in the USA. The competition involves student teams from
90

International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 –

all over the world designing and fabricating UAVs. Depending on the design and event objectives,
there are three classes in this competition: Micro, Regular and Advanced Class.
The objective of the Advanced Class, of the 2013 edition of SAE Aero Design Series, was to
design the most efficient aircraft capable of accurately dropping a three pound (3 lb) humanitarian
aid package from a minimum of 100ft off the ground. Though the class was mostly focused on
mission success, students were needed to perform trade studies to optimize empty weight and
anticipate repair build-up weight while meeting several aircraft design requirements.
The Advanced Class also entailed design of a DAS for the UAV and involved an array of
tasks that the DAS should accomplish to win high flight points, primary of which was to record
altitude and assist in precise expulsion of humanitarian cargo. The DAS objectives were:
1. Team must be able to provide real-time altitude reading at a ground station.
2. Team must be able to record the altitude at the moment they release the expellable cargo.
An important requirement of the altimeter was that it should have a precision of at least 1 ft.
The importance of DAS can be gauged from the fact that DAS failures were considered a missed
flight attempt and zero flight points were awarded for the same.
Furthermore, it’s evident from the design objectives that a sound and rugged wireless
Telemetry system was a necessity so as to transmit vital recordings which could assist the pilot on
the base station for precise cargo expulsion. This summarizes the DAS requirements for Advanced
class event of ‘SAE Aero Design Series 2013’ and to satisfy the same, this paper proposes a
comprehensive DAS and Telemetry system.
Keeping these requirements in mind, the system hardware comprises of:
• DS00 Laser Altimeter by Lightware Optoelectronics
• Mediatek GTP A010 GPS module
• Arduino Uno microcontroller
• Digi XBee-PRO modules
The GPS and altimeter modules consistently relay their readings to the microcontroller which
transmits the data to the base station. A laptop present at the base station displays a Graphical User
Interface (GUI) which presents all the measured data and also has a provision of a ‘Fire’ button to
initiate the cargo ejection. The XBee-PRO modules can transmit in a large range of 1 kilometre
radius giving the system a critical edge in terms of range of operation.
II.

BLOCK DIAGRAM OF THE SYSTEM

Figure 1: Block diagram

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A. LiDAR Altimeter
As stated earlier, precise measurement of real-time altitude and altitude measurement of the
UAV at the time of cargo deployment were a part of the DAS design objective. For doing the same,
different altitude measurement sensors and technologies were studied. There are 3 major
technologies for distance measuring equipment:
• LASER
• Ultrasonic
• Radar
The relative performance of distance measuring instruments based on these three different
technologies depends to some extent on the application. In our case, the UAV was to fly at an
average altitude of 100-150 feet. Under these circumstances, ultrasonic devices fall short because
their wide beam loses energy quickly and disturbances caused by background noise or air movement
dissipate their return signals. Radar technology is capable of long range measurement but it too has a
wide measuring beam that cannot easily pick out small targets. Laser technology is markedly
superior when accurate and long range measurements of small targets need to be made, owing to its
narrow beam.
Our requirement is high accuracy, long range and fast update rates, and hence Laser range
finders provide the leading edge. Employing LASER LiDAR (Light Detection and Ranging)
technology, the DS00 laser range finder by Lightware optoelectronics is selected. The key features
which prompted us to select this module are:
• It can measure targets over 100m away with accuracy; well within the maximum altitude that
the UAV would attain
• Has best resolution of 1cm; satisfying the competition requirement of minimum 1ft accuracy
• Can update distance results 100 times per second; helping to utilize ZigBee’s data-rate
efficiently

Figure 2: DS00 LiDAR module by Lightware Optoelectronics
The default method of communicating with the module is via a USB port. However a few
alterations on the circuit have enabled us to obtain the altitude values serially using TTL logic in
order to facilitate communication with Arduino Uno, which does not have a dedicated USB
communication port. The transmitter and receptor of the DS00 module are mounted at the bottom of
the fuselage, facing downwards towards the ground.
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B. Global Positioning System (GPS) module
As evident from the DAS design statement, specific usage of GPS modules isn't expected.
But to facilitate accurate and timely ejection of the humanitarian cargo, GPS module is employed to
obtain real-time location co-ordinates of the UAV. The significance of the GPS co-ordinates can be
depicted through the following calculations:

Figure 3: Package deployment distance measurement from the target
As depicted in Figure 3, the expelled cargo follows a projectile trajectory and hence precise
positioning of the UAV before expulsion is a must. An algorithm is followed by the GUI, present in
the laptop at the base station, to indicate the point when the package has to be ejected. It employs
following calculations:
Approximate Range of the projectile is calculated, assuming that the UAV is moving parallel
to the surface of the Earth:
Let the velocity of the UAV be u = 15m/s
Let the altitude of the UAV be H = 30m
Taking acceleration due to gravity to be g = 9.81m/s^2
Initial Velocity in x direction Ux = U = 15m/s
Initial Velocity in y direction Uy = 0m/s
Distance to be travelled in y direction = H = 30m = 0.5*g*(t^2)
….. as Uy = 0m/s
Therefore, we get t = (2*H/g)^0.5
Distance to be travelled in x direction (Range) S = Ux*t = U * (2*H/g)^0.5
That is, S = 15 * (2 * 30/9.81)^0.5
Thus, we get S = 37.096m
Thus, the humanitarian package should be deployed precisely 37.096m before the target, when the
UAV is travelling towards the target.
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This horizontal distance of 37.096m between the UAV and the target is computed by
obtaining the GPS co-ordinates. For the same, GPS module: Mediatek GTP A010 is chosen due to its
following features:
•
•
•
•
•

L1 Frequency, C/A code, 66 channels
Multi‐path detection and compensation
External Antenna I/O interface
Low Power Consumption: 48mA @ acquisition, 37mA @ tracking
Max. Update Rate: up to 10Hz (Configurable by firmware)

Figure 4: Mediatek GTP A010 module
At the base station, distance between two points is calculated using their GPS co-ordinates as
follows:
Distance = Acos[sin(lat1)*sin(lat2)+cos(lat1)*cos(lat2)*cos(lon2-lon1)]*6371
where ‘6371’ is approximate radius of earth in km, ‘lat’ is the latitude reading and ‘lon’ is the
longitude reading.
The method of communication between GTP A010 and Arduino Uno microcontroller is serial
with TTL logic.
C. ZigBee module
As demanded by the DAS Design Objective, wireless Telemetry is a critical component of
the problem statement and is essential for attainment of the required data, including altitude and GPS
readings, at the base station. Among the various wireless technologies available, the three under
consideration were:
1. ZigBee
2. Bluetooth
3. Wi-Fi

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Here is a comparative study of the three:
Parameter
Rage of operation
Extension

ZigBee
50-1600m
Automatic

10m
None

Operational duration
with a given power
supply
Complexity of
networking
Transmission speed
Frequency of operation

Longest

Medium

Wi-Fi
50m
Depends on the existing
network
Lowest

Simple

Complicated

Very Complicated

250Kbps
868MHz, 916MHz,
2.4GHz
65535
30ms
Low
128bit AES
High

1Mbps
2.4GHz

1-54Mbps
2.4GHz, 5GHz

8
Up to 10s
Low
64bit, 128bit AES
High

50
Up to 3s
High
SSID
Normal

Low
Easy

Low
Normal

Normal
Hard

Network nodes
Linking time
Cost of terminal unit
Security
Integration level &
reliability
Prime Cost
Ease of use

Bluetooth

Table 1: Comparison of ZigBee, Bluetooth and Wi-Fi wireless technologies
The parameters on which ZigBee was finally selected were:
1. Space and weight constraints on the UAV
2. Distance range of operation
3. Reliability
4. Support for large number of nodes
5. Extremely low setup time
6. Very long battery life
7. Secure
8. Ease of use
9. Low cost
Low data-rate isn’t a problem as only two sensor readings have to be transmitted and neither of
the two are bandwidth intensive. Also, the rate at which GPS co-ordinates are received is sufficient
for successful target distance computation.

Figure 5: Digi XBee-PRO module mounted on Arduino ZigBee shield
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Two XBee-PRO modules, from Digi International, are employed in the entire setup, which
have a range of 1km. One is present on board and transmits the critical measured parameters to the
base station. The other module is placed at the base station and supplies the received data to the
laptop via the USB port. Additionally, the base station also transmits a string to the on-board
controller, using these ZigBees, so as to initiate the package ejection sequence. Hence, it necessitates
full-duplex communication between the two ZigBees. This setup is programmed using the AT
Commands.

Figure 6: Digi XBee-PRO modules being programmed
D. Arduino Uno
There are many microcontrollers and microcontroller platforms available for physical
computing. Parallax Basic Stamp, MIT’s Handyboard and Arduino were the various options under
consideration. All of these tools provide microcontroller programming in an easy-to-use package.
Arduino simplifies the process of working with microcontrollers and also offers some peculiar
advantages over other systems:
• Inexpensive - Arduino boards are relatively inexpensive compared to other microcontroller
platforms. Pre-assembled Arduino modules cost less than Rs.2000.
• Cross-platform - The Arduino software runs on Windows, Macintosh OSX and Linux operating
systems. Most microcontroller systems are limited to Windows.
• Simple programming environment - The Arduino programming environment is easy-to-use for
beginners, yet flexible enough for advanced users to take advantage of as well.
• Open source and extensible software- The Arduino software is published as open source tools,
available for extension by programmers. The language can be expanded through C++ libraries.
In the Arduino family, Arduino Uno is selected as the on-board microcontroller. The general
features of Arduino Uno are as follows:
Microcontroller
ATmega328
Operating Voltage
5V
Digital I/O Pins
14 (of which 6 provide PWM output)
Analog Input Pins
6
Flash Memory
32 KB (ATmega328) of which 0.5 KB used by
bootloader
Clock Speed
16 MHz
Table 2: General features of Arduino Uno microcontroller
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Figure 7: Arduino UNO microcontroller
Location co-ordinates from the GPS module and the altitude readings from the LiDAR
altimeter are obtained by the microcontroller using two digital I/O pins, programmed as software
serial ports. The ZigBee module is interfaced with the Arduino Uno using the ZigBee shield. It
utilizes the only hardware UART (Universal Asynchronous Reception Transmission) port available.
The GPS module’s output follows the NMEA protocol which has output messages containing
data like latitude, longitude, airspeed, time etc. Out of these, only latitude and longitude are to be
used and hence the Arduino Uno is programmed so as to break down these incoming strings and
segregate only latitude and longitude data using MTK commands. On the other hand, the LiDAR
altimeter provides altitude readings in string format which is transmitted to the base station without
extra formatting. The sampling rate of the DAS is limited only by the data-rate of the Zigbee, which
is still well above the rate desired at the base station, for precise calculation of location co-ordinates
for humanitarian cargo ejection. Update rate of 5 readings/second (5 Hz) is obtained with the setup
but this varies slightly depending on the ambient conditions which affect Zigbee’s operation.

Figure 8: Altimeter readings obtained during testing on COM port of laptop

97


Figure 9: NMEA sentences from GPS obtained on COM port of laptop
E. Graphical User Interface (GUI)
The GUI at the base station provides a visual experience of the critical parameter
measurements. It incorporates the readouts for latitude, longitude, airspeed and a ‘Fire’ button for
package deployment. This button, when pressed, sends a string to the on-board microcontroller,
which identifies it as a trigger for initiating the ejection.

Figure 10: Screenshot of GUI on the laptop
The GUI uses Python language and is made using the ‘Eclipse IDE’.

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III.

CONCLUSION AND FUTURE SCOPE

A complete DAS and wireless Telemetry System for a UAV have been designed and
implemented. Apart from conforming to the design requirements of ‘SAE Aero Design Series’, it is a
fully functional unit which can be placed on any UAV. It proves to be an invaluable tool for assisting
the flight and mission requirements of the UAV. The future scope from here is to explore suitable
cameras and Telemetry options with wider bandwidth so as to transmit live video feed from the UAV
to the base station. Additionally, measurement of critical parameters such as remaining fuel and
airspeed can also be undertaken.
IV.
[1]
[2]
[3]
[4]
[5]
[6]
[7]

[8]
[9]
[10]
[11]

[12]

[13]

[14]

[15]

[16]

REFERENCES
About SAE AERO International, https://www.sae.org/about/
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Taylor H.R, Data Acquisition for Sensor Systems
XBee-Manual.pdf, http://www.digi.com/pdf/ds_xbeemultipointmodules.pdf
Introduction to Zigbee, http://xbee.wikispaces.com/Conclusion
Di Paolo Emilio Maurizio, Data Acquisition Systems: From Fundamentals to Applied Design
Eftichios Koutroulis and Kostas Kalaitzakis, Nov 2001, “Development of an integrated dataacquisition system for renewable energy sources systems monitoring” [online], Renewable
Energy 28 (2003) 139–152,
http://www.veritechmeasurements.com.au/papers/Monitoring%20of%20renewable%20energ
y%20systems%20_science.pdf
SAE Aero 2013 rules.pdf, http://students.sae.org/cds/aerodesign/rules/rules.pdf.
Arduino - Introduction, http://arduino.cc/en/Guide/Introduction.
GTP A010 datasheet.pdf, http://www.asichip.com/ceshi/pdf-new/SkyNav_SKG11B_DS.pdf.
Dr. Aditya Goel and Ravi Shankar Mishra, “Remote Data Acquisition Using Wireless Scada System” [online], International Journal of Engineering (IJE), Volume (3) : Issue (1),
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.301.4694&rep=rep1&type=pdf.
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AUTHORS

Dr. Deepak Vishnu Bhoir, IEEE member since 2005, has received
B.Sc.(Tech) degree from University of Bombay in 1990, thereafter finished the
Masters in Electronics Engineering from University of Mumbai. He has obtained a
Ph.D. in Biomedical field from VJTI, Mumbai. His specialization is in ‘Biomedical
Instrumentation’ and ‘VLSI Design’. He has a teaching experience of 22 years and
is currently the Head of Department, Department of Electronics, Fr. Conceicao
Rodrigues College of Engineering.

Ramesh Kamath is pursuing degree of ‘Bachelor of Engineering’ in
‘Electronics Engineering’ from Fr. Conceicao Rodrigues College of Engineering,
Bandstand, Bandra (West), Mumbai – 400050, affiliated to Mumbai University. His
current research interests include ‘Automotive Electronics’, ‘Embedded Systems’
and ‘Avionics’.

Siddhesh Nadkarni is pursuing degree of ‘Bachelor of Engineering’ in
current research interests include ‘Image Processing’, ‘Avionics’ and ‘Embedded
Systems’.

Kundan Srivastav is pursuing degree of ‘Bachelor of Engineering’ in
current research interests include ‘Power Electronics’, ‘Avionics’ and ‘Embedded
Systems’.

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IJECET Data Acquisition and Telemetry for UAVs

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