INTERNATIONAL JOURNAL OF ELECTRONICS AND COMMUNICATION ENGINEERING & TECHNOLOGY (IJECET)

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1 INTERNATIONAL JOURNAL OF ELECTRONICS AND COMMUNICATION ENGINEERING & TECHNOLOGY (IJECET) International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 ISSN (Print) ISSN (Online) Volume 4, Issue 5, September October, 2013, pp IAEME: Journal Impact Factor (2013): (Calculated by GISI) IJECET I A E M E DATA ACQUISITION SYSTEM AND TELEMETRY SYSTEM FOR UNMANNED AERIAL VEHICLES FOR SAE AERO DESIGN SERIES Ramesh Kamath 1, Siddhesh Nadkarni 2, Kundan Srivastav 3, Dr. Deepak Vishnu Bhoir 4 1,2,3 UG Students, Department of Electronics Engineering, 4 Professor and Head, Department of Electronics Engineering Fr. Conceicao Rodrigues College of Engineering Fr Agnel Ashram, Bandstand, Bandra (W), Mumbai, Maharashtra, India. Pin Code: 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

2 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 91

3 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 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. 92

4 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 = m Thus, the humanitarian package should be deployed precisely m before the target, when the UAV is travelling towards the target. 93

5 This horizontal distance of m 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: acquisition, 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 94

6 Here is a comparative study of the three: Parameter ZigBee Bluetooth Wi-Fi Rage of operation m 10m 50m Extension Automatic None Depends on the existing network Operational duration Longest Medium Lowest with a given power supply Complexity of Simple Complicated Very Complicated networking Transmission speed 250Kbps 1Mbps 1-54Mbps Frequency of operation 868MHz, 916MHz, 2.4GHz 2.4GHz, 5GHz 2.4GHz Network nodes Linking time 30ms Up to 10s Up to 3s Cost of terminal unit Low Low High Security 128bit AES 64bit, 128bit AES SSID Integration level & High High Normal reliability Prime Cost Low Low Normal Ease of use Easy Normal Hard 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 95

7 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 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 96

8 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

9 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. 98

10 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. REFERENCES [1] About SAE AERO International, [2] DS00 - Laser Range Finder Manual_Rev_00.pdf [online], [3] Taylor H.R, Data Acquisition for Sensor Systems [4] XBee-Manual.pdf, [5] Introduction to Zigbee, [6] Di Paolo Emilio Maurizio, Data Acquisition Systems: From Fundamentals to Applied Design [7] Eftichios Koutroulis and Kostas Kalaitzakis, Nov 2001, Development of an integrated dataacquisition system for renewable energy sources systems monitoring [online], Renewable Energy 28 (2003) , y%20systems%20_science.pdf [8] SAE Aero 2013 rules.pdf, [9] Arduino - Introduction, [10] GTP A010 datasheet.pdf, [11] Dr. Aditya Goel and Ravi Shankar Mishra, Remote Data Acquisition Using Wireless - Scada System [online], International Journal of Engineering (IJE), Volume (3) : Issue (1), [12] Smita B. Garde and Prof. S.L.Kotgire, Coalmine Safety System with Zigbee Specification, International Journal of Electronics and Communication Engineering & Technology (IJECET), Volume 4, Issue 2, 2013, pp , ISSN Print: , ISSN Online: [13] Sarang D. Patil. and Prof. S.N. Pawar, Wireless AMR System using Zigbee Technology, International Journal of Electronics and Communication Engineering & Technology (IJECET), Volume 3, Issue 2, 2012, pp , ISSN Print: , ISSN Online: [14] Deepalakshmi.R, Jothi Venkateswaran C, A Survey on Mining Methods for Protein Sequence Analysis: An Aerial View, International journal of Computer Engineering & Technology (IJCET), Volume 3, Issue 2, 2012, pp , ISSN Print: , ISSN Online: [15] Ansari Md.Asif, Md Riyasat, Prof.J.G.Rana, Vijayshree A More and Dr.S.A.Naveed, Green House Monitoring Based on Zigbee, International Journal of Computer Engineering & Technology (IJCET), Volume 3, Issue 3, 2012, pp , ISSN Print: , ISSN Online: [16] Abhishek S H and Dr. C Anil Kumar, A Review of Unmanned Aerial Vehicle and Their Morphing Concepts Evolution and Implications for the Present Day Technology, International Journal of Mechanical Engineering & Technology (IJMET), Volume 4, Issue 4, 2013, pp , ISSN Print: , ISSN Online:

11 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 , 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 Electronics Engineering from Fr. Conceicao Rodrigues College of Engineering, Bandstand, Bandra (West), Mumbai , affiliated to Mumbai University. His current research interests include Image Processing, Avionics and Embedded Systems. Kundan Srivastav is pursuing degree of Bachelor of Engineering in Electronics Engineering from Fr. Conceicao Rodrigues College of Engineering, Bandstand, Bandra (West), Mumbai , affiliated to Mumbai University. His current research interests include Power Electronics, Avionics and Embedded Systems. 100