to the PDF file. - College of Engineering, Forestry, and
Contents
1. 4 INITIAL RESEARCH Much of the work done thus far has been research The innovative nature of the project required knowledge from many fields of study and the sources found in this research reflect this Presented below are selections of some sources which have proven to be of the most benefit toward the evolution of the design 4 1 Mechanical One source that has proven particularly useful in designing powertrain elements is Basic Helicopter Aerodynamics Second Edition by J Seddon and Simon Newman part of the AIAA Educational Series This book provides explanations of the fundamentals behind rotor craft flight The equations and explanations guided the derivations performed to gain a fundamental understanding of how the rotors produce thrust and the power required to produce it From this it was possible to find suitable propeller dimensions for the thrust required suitable motors to turn the propellers which then dictated the amperage of electronic speed controllers necessary and a suitable battery voltage 4 2 Avionics The majority of the concepts related to the avionics system are straightforward but communication with the Pixhawk flight controller requires the use of a new protocol and library which has not yet been used in the way we have intended The first major source is the library s traditional code documentation 1 This includes comments within its code a web page describing the many available enumerations and a c2. shown in Table 1 Table 2 Fastener testing results Bolt type Nut type Loading at failure Failure mode lbs 8 24 Nylon 8 24 Nylon 2 Sheared threadings of the nut and bolt 10 32 Nylon 10 32 Nylon 3 Sheared threadings of the nut and bolt 52 Zine 624 Zine NA 6 24 Brass 6 24 Brass NA 6 24 Brass 6 24 Zinc NA 6 24 Zinc 6 24 Nylon Sheared threads in the nut 10 32 Nylon 10 32 Brass 95 Rupture at the head of the bolt As a failure load of roughly 10 lbs was desired the combination of 10 32 nylon bolt 6 24 Zinc 6 24 Brass NA and brass nut was chosen being the closest to the desired value This combination also resulted in a consistent and predictable failure mode of shearing the bolt at the head another desired trait A drop test was conducted which consisted of dropping the system at multiple angles from five feet to ensure that the failure piece performs as expected The nylon bolt was shown to shear at the head for these heights allowing for quick reassembly of the drone with minimal damage to critical components 5 1 2 Thrust Calculations Another analysis task which fell under the mechanical team s skillset was selecting propellers capable of producing enough thrust to lift the system The propellers are the driving component for the entire propulsion system design Once propellers are selected motors need to be selected which are capable of spinning them and electronic speed controllers which are capable of handl
3. A foil tape coated divider also provided two compartments that were EMI shielded to allow the receiver to be placed within its own shielded compartment A picture of the drone displaying this box is shown in Figure 4 Figure 4 Box for protecting electronics and insulating receiver from EMI 14 5 1 4 Landing Gear Lastly the mechanical team implemented landing gear that doubled as an attachment point for the antenna The landing gear material was chosen to be PVC so that it would have no interference with the antenna and for its availability and cost effectiveness The landing gear was connected through the same nylon bolt connecting the square tubing to the baseplate This was done so that the nylon piece would fail upon hard landing on the gear or an arm A 45 degree attachment piece was used to offset the landing gear legs away from the frame creating a lever arm to help break the nylon connection upon hard landing landings absorbing a portion of the impact The attachment point of the antenna was done through two 3D printed pieces that attached to each leg of the landing gear and the antenna boom The 3D printed pieces were chosen for their customizable dimensions to fit the boom and PVC and because of the ability to make and carry extra 3D printed parts in the field again allowing for more field repairable failures The landing gear can be seen in Figure 5 below Figure 5 Landing gear attached to frame 5 1 5 Battery Bre
4. thick Square Tubing Aft 30 00 i Machined 6061 Aluminum Plate 8 x8 x1 8 48 34 Foam Padding 12 x12 x3 4 17 44 Miscellaneous Bolts and Connectors 20 00 Failure Component Weak Link in Arm Structure 10 00 Machining of Base Plate and Arms 50 00 E 100 00 850KV 311W brushless outrunner 30A2 4S 17 carbon fiber 8400mAh 351P 30C 3DR radio set with micro USB 23 35 Lipo charger PixHawk and GPS module Class 1 100M dongle Raspberry Pi B kit 5V 5600 mAh USB charger 20 35 14 39 97 64 05 100 00 12 35 279 98 14 99 69 99 9 99 200 00 h ab ab ab ab ab ot ot oh fe de 230 71 230 71 AOR AR8200 Mark III B 909 00 909 00 USB8200 or USB 8200A 99 00 arts and unforeseen costs Figure C1 Estimated Budget 46 Funding of 3 000 00 Dr Flikkema Dr Shafer D4P Funds Figure C2 Funding contributions Frame Purchases Frame Purchases Turnigy Multistar 4220 880Kv 16Pole Multi Rotor Outrunn Turnigy Multistar 20 Amp Multi rotor Brushless ESC 2 45 16x4 Carbon Fiber propellers for DJI S800 L H and RHR Zippy Compact 5800mAh 3S 25C Lipo Pack Turnigy E3 Compact 2S 3S Lipo Charger 100 240v US pl Shipping Fee Turnigy Multistar 4220 880Kv 16Pole Multi Rotor Outrunn 16x4 Carbon Fiber propellers for DJI S800 L H and RHR shpping New Turnigy Multistar 20 Amp 20a Multi rotor Brushless E 2 New Turnigy Multistar 20 Amp 20a Mutti rotor Brushless ESC 24S US Turnigy Multistar 4220 880Kv 16Pole Mu
5. 2 Three Element Yagi Antenna The three element antenna provides a lot more gain when compared to the two element Yagi at the expense of being less compact In contrast the three element antenna has a similar beam width but a greater beam length giving it a more directional azimuth plot as shown in Figure 11 above and Figure 13 below Gain 6 dBD F B 30 dB Beamrith 99 deg Figure 13 Three element Yagi antenna with azimuth plot 23 5 3 3 Five Element Yagi Antenna The five element antenna provides the largest gain Although this antenna may be lengthy it allows for more precise signal receiving capabilities as shown on the azimuth plot in Figure 14 CANC 27 5 MHz Elevation Plot Cursor Eley 0 0 deg Azimuth Angle 0 0 deg Gain 8 1 dBref Outer Ring 8 1dBret 0 0 dBmax Slice Max Gain 6 1 dBref Elev Angle 0 0 deg Front Back 43 68 dB Beamvvicth 70 4 deg 3dB 324 5 35 2 deg Sidelobe Gain 6 93 dBref Elev Angle 102 0 deg Front Sidelobe 15 03 dB Figure 14 Five element Yagi antenna with azimuth plot 5 3 4 Final Antenna After speaking with other field and scientific researchers biologists and hobbyists and undergoing our own research it became clear that the five element antenna would be our best choice However due to our constraints on length and weight we deemed it impractical Therefore the decision was clear that we needed to go with the second most effective configuration which is the
6. BR 1 cr Ian BJ 2 Which results in a coefficient of thrust equation fxs 5 3 a Ta 127DB arctan M gt p 9TDB 1 B Ory T 62D 2V2 8 Nca And a coefficient of power equation Causing A to become 2 keza Cp 0C P BZ B Do Using a value of B 85 corrected the thrust predictions however power input predictions were still far lower than the data indicated Part of the issue is the lack of detailed information regarding Cp or which airfoil is used Because of this the second term is accounted for using a multiplier in front of the first term While the multiplier can be manipulated to help best fit the data set values which do so are much larger than expected This suggests that there may be an assumption made in the derivation of the coefficient of power which does not hold up well for propellers with smaller nominal dimensions Concerns could arise from some of the later statements regarding corrections done to help fit a sparse data set While the data set is sparse all corrections were aimed to underestimate thrust and over approximate power Keeping this in mind a design resulting from this analysis should be at worst more than capable of doing what is required of it 42 SpropB m SPredicts maximum thrust produced and power required for a given propeller SWritten by Alex Moore Slast revision 11 7 14 function T P Om propB D M KV V sTakes inputs of Diameter D and Pitch M in inches motor KV ra
7. all frequencies not in the specific range we are seeking An example of signal data before and after the use of this filter can be seen below Recorded by pi after 3 rotation on April 13 2015 05 ia 07 us 02 Normalized Frequency xx rad sample Figure 20 Signal data before filtering Filtered out noise for the 3 rotations rocording 06 Time s 08 is 0 2 1 Normalized Frequency xx rad sample Figure 21 Signal data after Butterworth filter 29 6 ITEMIZED BUDGET There are two relevant budget reports that have been created during the course of this project The first is an estimated budget that was created early in the semester before a meeting with the Dean of the College of Engineering in which we attempted to gain funding since at the time we only had 500 to use for a project that was estimated to need over 2 000 in parts This will be shown in Figure 1 of Appendix C We ended up receiving 2500 more in funding from Dr Shafer and Dr Flikkema The respective contributions to our final budget can be seen in Figure 2 of Appendix C The second is the final expense report which consists of all the purchases that were made throughout the project This will be shown in Figures 3 through 5 of Appendix C There is a significant difference between the estimated budget and the expense report for the telemetry team We estimated that the telemetry team would spent the most by far because the receiver is the
8. and display The avionics and telemetry teams collaborated to create code to accomplish this and an example graph of signal amplitude over time can be seen in Figure 23 below Filter Signal with Upper Threshold Magnitude 0 8 0 5 10 15 20 25 30 35 Time seconds Figure 23 Filter signal data plotted with respect to time From this data the greatest amplitude and time can be determined using MATLAB s sorting functions An example MATLAB output can be seen in Figure 24 below demonstrating this The maximum magnitude is 0 906524 which occured at 34 2625 seconds Figure 24 MATLAB output of magnitude and time data Finally this data can be matched with the corresponding GPS coordinate at that time to give a heading of the bat s location This overall process is effective and serves to show that a wildlife telemetry drone can be a useful tool for researchers in locating tagged bats However 32 this system is far from perfect In order to improve the usability and effectiveness of this design we would recommend adding a digital receiver with auto adjusting gain and a digital output We would also recommend a non conducting frame to reduce both weight and electromagnetic interference from the frame itself Finally we would recommend the implementation of long range digital communication so that long range override is possible without the use of an additional RC controller With the basic design complete futur
9. data Easily fits in a hiking backpack approximately 50x30x30cm Usability No additional training required to operate Allows signal and direction data to be transferred to an external device Only predictable field repairable damage sustained for 5ft drop Safety Manual override of autonomous flight systems is available at all times Drone power circuit disengages after drone sustains a fall of 5ft Liability Complies with FCC and FAA regulations Of these specifications all have been fulfilled except for three The ways in which these specifications were fulfilled will be discussed later in report The three that were foregone are shown below e Flies a distance of at least three kilometers with telemetry equipment attached e No additional training required to operate e Drone power circuit fuse must break after drone sustains a fall of 5 ft The first of these 3 kilometer flight was found to be unnecessary for the drone in its current state For researchers it would be ideal for the drone to take fully autonomous triangulation flights However FCC Federal Communications Commission and FAA Federal Aviation Administration regulations disallow UAV flight outside of the field of vision of an operator As a result this specification conflicted with our requirement to adhere to these regulations and had to be foregone as a result As a result of the same FCC and FAA regulations we determined that it w
10. order to develop a coefficient which is more useful when finding suitable motors dQ dCo 2 pA QR 2R 1c E dCo aap CL Cp r dr Noting that P QQ it can be seen that Cg and Cp are identical Through some simple substitutions we can find that 1 dCp dCr zocor dr Integrating yields 1 Cp ACr gI D Which simplifies further to ch 1 E E Cp 7 goto Where Cp is the coefficient of drag for the airfoil at zero angle of attack Here our assumption of uniform inflow yields much larger errors To correct this an empirically derived correction factor k is used which only affects the first term 3 cf me i C P k o0C Do v2 8 41 During the development of a MATLAB code to calculate the maximum thrust produced by a given propeller very little data had been acquired for use of comparison despite exhaustive research This limited data set however did offer some insight for other possible considerations When compared to the data sets predictions showed much higher thrust produced with much lower power inputs to the system To attempt to correct this tip vortex effects were considered A simple way to do this is to consider only a portion of the blades as producing lift but the entirety producing drag This however means that the integral no longer simplifies so nicely We change the limits of integration to 1 B Cr 500 Or Ar dr 2 Jo As well as changing the area to an effective area A
11. these substituting and solving for Ap we find 1 Apr 5p ve Vo Plugging into our thrust equation from earlier 1 T 5 pA ve vo Then setting our two trust equations equal to one another and simplifying 1 2 2 3 PA ve Vo PUi Ve Vo 2V Ve Vo Noting that at some point far upstream of the actuator disk the velocity is very close to zero we find that Vo 0 Therefore 20 Ve Applying this new information and the assumption of zero velocity far upstream to our first thrust equation we find that T 2pAvf Solving for the induced velocity v 36 This induced velocity is useful as we introduce blade element theory as it affects the angle of attack for the airfoil shape of some blade element We will consider a blade element with width dy and chord length c at some location y along the span of a blade with radius R spinning at angular velocity as shown in Figures A2 and A3 below dy Figure A2 Blade strip coordinates 13 SN Q Figure A3 Propeller disc viewed from above 13 dT dL Blade Section Disc Plane Qy Figure 4 Blade element flow conditions and forces 13 Here 6 is called the pitch angle seen in Figure 4 This is not to be confused with the pitch of a propeller we ll call it M which results from the pitch angle of a propeller and can be understood as the distance a propeller would travel forward through a solid substance during a 37 360 rotati
12. worked together to decide what designs and components are best suited to create a working design that will lead to a product for the Forestry Department to use in the field These design decisions and their justifications are shown below divided according to subteam 5 1 Mechanical The mechanical team was in charge of constructing a physical system to lift the telemetry equipment for tracking flights The deliverables for the mechanical team included a backpackable frame capable of flight landing gear to protect components from damage upon a possible crash and protective systems for the battery and electronics 5 1 1 Prototype Frame The mechanical team began by constructing a prototype frame to begin testing Among these initial tests was a failure point test to ensure the drone only receives easily repairable damage in the event of a crash The completed test was designed to find a fastener configuration of the arm to the baseplate that would allow failure of the fastener near 10 lbs which is below the failure point of both the 6061 aluminum arm and the 7075 aluminum base plate A 12 inch arm was cut from the aluminum and holes were drilled in the base plate and the arm A bolt and nut was then used to connect the arm to the base plate The preload of the bolt was assumed to be zero as the nut was tightened to finger tight The arm was end loaded until failure to simulate and end load from impact with the ground The results of the test are
13. 05 10 5 800 18 5 315 1 27 10 5 900 TIal 133 075 EE ty 800 14 8 260 1 05 11 7 900 11 1 188 0 89 12 6 800 14 8 276 d2 12 6 900 11 1 195 1 01 13 4 900 1 1 194 1 04 SInitialize matrices for theoretical and calculated Coeff of Thrust CE Pl CTR tor i 1 15 k propB data i 1 data i 2 data i 3 data i 4 CT CT data i 1 k k2 16 9 81 data i 6 pi 0254 data i 1 4 data 1 3 data i 4 2 2 CTR CTR data 1 1 k2 collect desired outputs from results sneed to make T and P outputs of function and collect corresponding Soutputs end plot CT yI CECs 2 0 hold on plot CTR 1 CTR 2 scalculate difference between calculated and actual E CT 2 CTR 2 APPENDIX B Avionics State Machine Ground Station Raspberry Pi Ground Station Launch Data Process Processing Debug Various Debug Commands Tools Send all Postprocessing Collected Data Display Map Pixhawk Return to Calculate General Launch Flight Purpose and Land Path Input Output Last Waypoint Reached Next Write Data Waypoint to Disk Not Last Waypoint Send GPS Receive GPS Data Data Figure B1 State Machine for Drone Control Systems 44 Arm Pixhawk Disarm Pixhawk Minimum Throttle Maximum Throttle Start Recording Stop Recording Debug Routines Only for Development Purposes 45 APPENDIX C Budget and Expense Reports i 1 x1 1 8
14. 5V Micro USB HDMI Port 4 pole 3 5mm jack stereo audio amp composite video CSI Camera Connector Figure 8 Raspberry Pi 9 In terms of software the Pi is running Raspbian an ARMvV6 version of Debian It is configured to not use a graphical interface on boot but has OpenBox and Tint2 installed for an interface As part of this project we have written a program to perform tasks on the drone that is currently unnamed and has been referred to as the program or custom software It is written entirely in C and is placed in the Code directly of the home directory A boot script in Debian s init d configuration runs this program automatically This program receives commands from the ground station 5 2 3 Ground Station The ground station is an easy to use Android application but could take any form Android devices however always have GPS devices do not require external peripherals and 19 are easily replaceable Therefore this is the form we chose for our ground station With the exception of holding the safety switch on the drone itself all control of the drone can and should be done through the ground station Android Studio was used in developing the ground station and is required in order to place the app onto an Android device as there are no packages an APK file prepared Once finalized a package should be made The app is capable of running on any recent device but the device should have a sufficient resolut
15. Wildlife Telemetry Drone WTD Willem Arjana Chris Gass Stephen Kuluris Reejay Martinez Alex Moore Leonard P Peshlakai Trevor Petersen Lucas Philipsen Dylan Steyer Northern Arizona University Engineering Department May 1 2015 Wildlife Telemetry Drone Team Northern Arizona University To Dr Michael Shafer We are pleased to submit this report documenting the research analysis and results for the drone for wildlife telemetry that we ve worked on throughout this semester We d like to thank you for providing us with the opportunity to work on such an exciting project and the electrical engineers in particular would like to thank you for reaching out to our EE 476C capstone class to bring us on board We began this project as a tool to aid in the research of bat habitats for use in the College of Forestry Engineering and Natural Sciences at Northern Arizona University The current methods for conducting such research are strenuous and time consuming due to the requirement of finding vantage points of high ground in order to get a clear signal from radio telemetry tags attached to the bats to triangulate their location This projects aims to develop an autonomous drone to collect wildlife radio telemetry measurements in a more efficient manner by flying at multiple locations expediting the data collection process To achieve this a quadcopter style drone was built and outfitted with an antenna The drone flies straight up ro
16. a linear twist of the blade along the span in other words making the pitch angle vary linearly with the radius we can reduce the errors introduced to less than a few percent A convenient way to do this is to make the reference pitch at three quarters the radius of the blade as such 0 675 r 0 75 Oy Where 0 7 is the pitch angle at three quarters the radius and 6 is the rate of change of the pitch angle with r 0 is a negative value The convenience of doing this is that the result of integrating our differential coefficient of thrust equation with this substituted in for O is the same Due to the nomenclature for nominal dimensions of hobby propellers being the diameter in inches followed by the pitch at three quarters the radius it is assumed throughout the rest of this analysis that hobby propellers use linear twist based on this convention Now recall that And Plugging v into A we can find that 40 Cr A 2 Substituting this into our equation for coefficient of thrust we obtain a quadratic equation for Cr Noting that 32D Where M is the nominal pitch of the propeller and D is the diameter the solution to the quadratic is as follows 3 9 12nD 4M 3 t48 t Wea arctan saD 67D Neca 4M 075 arctan 2 Cr Where N is the number of blades c is the mean chord length of the blades and a remember is the lift curve slope 5 7 here Let us revisit our equation for coefficient of torque in
17. akaway As stated in the specifications a battery breakaway was not implemented this semester Current drones on the market do not feature such a device making the design of this breakaway its own ambitious project apart from this one Research was done into a level 15 actuated device using the landing gears affixed to the arms to pull the battery connector away from the battery However a prototype revealed the actuation was not enough to effectively pull the connector apart The lever design also only allowed for actuation of the battery breakaway if landing was upon the arms Side impacts therefore would not disable the battery An inertial mass system was also considered to separate the connector However this method required a more easily disconnected battery connector than was currently implemented A magnetic connector was considered but the high current from the battery prevented current designs from being used requiring a new magnetic system to be designed and built This was deemed to be beyond the scope of this project as a new connector would require extensive testing to ensure it could reliably handle the current and not disconnect unexpectedly as this could be catastrophic during high altitude flights The use of an inertial disconnect system in combination with a magnetic connector was considered the most viable option with more research and development being necessary in the future to implement this idea To prevent fire
18. cations that is compatible with frame Design failure points to allow for field reassembly after a crash Ensure that final design can be disassembled to fit in a standard backpack 3 2 Avionics Find or create an avionics system that can fly the drone by itself Find or create a controller that will control all the components of the drone and find or write open source code for that controller to connect all of the electronic systems together Create a manual override system using an RC controller Create a ground station that will receive and display info to the user that includes triangulation data and the location of the drone every x minutes through either Bluetooth or Wi Fi Ensure that any electromagnetic interference EMI generated by the motors does not interfere with the telemetry equipment Wire all of the components together in a safe and compact manner 3 3 Telemetry Design a prototype three element Yagi Uda antenna commonly known as a Yagi antenna Construct a telemetry system including the aforementioned antenna and a receiver that can output data to the drone s on board computer Ensure that antenna and receiver are not receiving extra noise and or interference from either the motors any avionics circuitry or other miscellaneous electronics Use MATLAB to create a filtering algorithm to eliminate any remaining noise and or interference and display the greatest amplitude paired with time and GPS heading at that time
19. chanical Final Expense Reporta ue deen aati 47 Avionics Final Expense Report 2222 c2ctaveccisel ac adesetseeseasdueciantenatealacctatasentats 48 Telemetry Final Expense Report and Total Expenses ooonoccnnnccnonononcconnnnnnnon 49 Comparison between the estimated and final budget for each subteam 50 vi 1 INTRODUCTION The Northern Arizona University Forestry Department henceforth referred to as NAUFD currently tracks bat colonies throughout large areas in the forests of Northern Arizona Bats are captured at night while they are active and a small transmitter is placed upon each of the captured bats Field researchers can then track the transmitted signal to the location of the roosting bats during the day In order to locate these colonies the signal from the transmitter must be recorded at multiple sites By noting the direction at which the signal was recorded the location of the colony can be triangulated However in order to obtain a usable signal high vantage points are required ideally on a ridge or small mountain The researchers must cross country hike to reach a suitable site before recording the signal wasting valuable time and limiting where and when the signal can be recorded The current process allows bat colonies to be located but there is an opportunity to improve this process One method for improving the current locating process is the use of an Unmanned Aerial Vehicle UAV otherwise known as a drone A dron
20. e Future Appendix A Thrust Analysis Appendix B Avionics State Machine Appendix C Budget and Expense Reports iv List of Tables and Figures Tables Kable le Project PECAR iia 2 Table2 Fastenertesung Tesulis foes o a a as 9 Figures Figure 1 Final frame modelled in CAD aiii iia das 11 Figure 2 Spring pin connection for detachable arms ooconccnnnccnononoccnonannnancnnncnonccnnncnnn noo 11 Figure 3 Arm connected to dro A 12 Figure 4 Box for protecting electronics and insulating receiver from EMI 13 Figure 5 Landing gear attached to frame A 14 Figure 6 Early prototype demonstrating Pixhawk and RPi function ee eee 13 Figure 7 Pixhawk flight controller tai ti dai Baden 17 Figure Raspberry Pl O ES 18 Figure 9 Screenshot of the ground station s flight SCrEOM oooonoccnncnonccocanocononcnnnonncnrncnnoo 19 Figure 10 Screenshot of the ground station s debug Screen ooooconncconccoconocononcnnnnnncnnncnnoo 20 Figure 11 Antenna gain Comparison cecccicccniccnnnncnnonnncnnncennnn canon nan rincn none cane ncanne cane and 21 Figure 12 H element Yagi antenna with azimuth plot ooconnncnnnncnoccconannnnnnonncconnnnnncnnnano 22 Figure 13 Three element Yagi antenna with azimuth plot oooncnnnncnnccnoccnnoncnonnnannnnnnnnos 22 Figure 14 Five element Yagi antenna with azimuth plot oooooonccnonccnnccnoncnnoncnonccannnonnnon 23 Figure 15 Final antenna modelled mCA Diana ici 24 Figure 16 Equatio
21. e testing and system refinements should lead to a well developed functioning tool to aid in research of animal habitats and roosting patterns while providing a foundation for future projects of a similar nature 33 REFERENCES 1 L Meier MAV Link Documentation Internet https github com mavlink mavlink Nov 21 2014 2 3DRobotics Communicating with Raspberry Pi via MAVLink Internet http dev ardupilot com wiki raspberry pi via mavlink Nov 10 2014 3 UAV Dev Board Internet https code google com p gentlenav Jul 22 2013 Nov 19 2014 4 T Hubing and N Hubing Practical Electromagnetic Shielding Internet http www learnemc com tutorials Shielding02 Practical Shielding html Sep 29 2014 5 R Brigham Transmitter attachment for small insectivorous bats Internet http www holohil com bd2att htm Oct 14 2014 6 David Dalton Sr Systems Design Engineer Photometrics Interview Tucson AZ October 6 2014 7 Aluminum Distributor ver 11 Internet http www aerospacemetals com aluminum distributor html Nov 21 2014 8 Pixhawk Overview Internet http copter ardupilot com wiki common autopilots common pixhawk overview Nov 10 2014 9 Raspberry Pi Model B Internet http www cnet com uk products raspberry pi model b plus Nov 10 2014 10 Antenna Types Yagi Internet http www cbantennaguide com Yagis htm No
22. e would allow for the signal from the transmitter to be recorded from more locations as the drone could be flown vertically to a height where it can receive the signal as effectively as a researcher would on a ridge or hill The cross country hiking currently necessary to reach those sites could therefore be eliminated A drone could also potentially fly to multiple locations and record the signal at each allowing for triangulation of a colony s location without requiring the field researcher to hike extensively The team has been tasked with designing and building a drone that can be used to record these signals allowing for easier tracking of the bat colonies While initially completing only vertical flight to record signals the drone is to be built with the intent of taking recordings at multiple points in one flight 2 SPECIFICATIONS Achieving reliable flight with a UAV is a complicated process and the addition of signal acquisition adds to the complexity of the system Due to this complexity a large number of specifications were assigned by the client Dr Michael Shafer The following list outlines the specifications needed for an initial drone to be completed Table 1 Project specifications Specification Takes off vertically and lands within 5m of the same point Flight Telemetry Flies a distance of 3km with telemetry equipment attached Accurately outputs a signal amplitude and GPS pairing according to telemetry
23. ear that also allowed a connection point for the antenna The final frame design constructed with CAD software is shown in Figure below 11 Figure 1 Final frame modelled in CAD The detachable arms use a spring pin connection that allows the square tubing arm to slide inside a permanent square tubing attachment to the baseplate This connection is shown in Figure 2 below Figure 2 Spring pin connection for detachable arms 12 The arm then snaps into the permanent square tubing on the base plate This design was chosen for its quick release ability which aids in meeting the specification of having a collapsible vehicle Holes were drilled through the arms further lightening them This can be seen in Figure 3 below Figure 3 Arm connected to drone The permanent square tubing on the baseplate used in the spring clip attachment of the arms were connected using designed failure points These failure points included a nylon 10 24 bolt attachment as was determined necessary by the experiments outlined in Table 1 The nylon bolt and brass nut held the tubing from a vertical displacement while two nylon button fasteners held the tubing from rotating The placement of the rotation failure pieces was first tested on the prototype baseplate Holes were drilled so that the nylon rotation prevention pieces were flush with the square tubing for one test and with a 1 10 inlay on the square tubing piece The 1 10 inlay ga
24. escription 36 X3 4 X 1 116 ALUMINUM SQUARE TUBE MILWAUKEE 5 16 BLK OXIDE DRILL BIT 36 X 1 4 ROUND ROD ALUMINUM Three rods Tax 2011 T3 Aluminum Round Rod 25 Dia Cold Finish 3ft 2011 T3 Aluminum Round Rod 25 Dia Cold Finish 4ft Shipping Fee Tester to make a fraday s case Foil Tape 50yd tax 3 1 8 M M patch cable or AUX cord tax black amp red wires 10ft 14 awg solid Exterior Mounting Tape Black Flex Tubing tax Velcro 5 PK Spray Paint tax Boom mounting rod Carbon Fiber Arrows 35 00 tax 5138 21 Figure C5 Telemetry Final Expense Report and Total Expenses 50 Estimate Avionics Telemetry Mechanical Unforeseen Expenses Expenses Avionics Telemetry Mechanical Unspent Funds Figure C6 Comparison between the estimated and final budget for each subteam
25. hazards associated with the lithium polymer battery used in the drone a plastic case was implemented to provide puncture protection eliminating one major source of hazard to the battery A one inch thick layer of foam also padded the battery and all other electronics in the case preventing jostling or additional impact to the battery A battery breakaway should be implemented before full flights in the forest but the current safety features allow for safe test flights as development is continued 5 2 Avionics The avionics design considerations included three main components the flight controller the on board computer and the ground station The flight controller a Pixhawk and the on board computer a Raspberry Pi are in constant communication and make the entirety of the calculations in regards to flight Additionally their communication allows the Raspberry Pi to record data from the Pixhawk s sensors for telemetry purposes The stripped down system itself can be viewed in Figure 6 16 Figure 6 Early prototype demonstrating Pixhawk and RPi function The Pixhawk is a PID control system with many standard and feedback inputs which outputs pulse widths to the speed controllers thus maintaining flight The Raspberry Pi sets flight paths relative to the drone s location at the time of launch records different forms of data communicates with the ground station and is fully expandable Communication between the Pixhawk and Ra
26. ing the current loads of the motor To select propellers a code was developed 10 to approximate the maximum thrust a given propeller can produce and the power required to produce that thrust Several assumptions were made in this development due to the lack of detailed information available for off the shelf parts marketed to hobbyists who may not necessarily have an engineering background With the thrust approximation code complete the team assumed a total vehicle mass of approximately six pounds leading to a desired maximum thrust of about 12 pounds to maintain maximum control authority over the vehicle There were a few possible propellers which would be suitable including 15 x 5 5 carbon fiber propellers and 16 x 4 carbon fiber propellers The 16 x 4 propellers were selected because their lower pitch is better suited for hover applications and increases stability by damping out effects of small perturbations in motor speed For further details on the analysis performed and to view the developed code see Appendix A 5 1 3 Final Frame The mechanical design team has made many improvements from the prototype when fabricating the final frame Many design choices were made with client specifications in mind New aspects implemented in the final frame design were detachable arms nylon failure points at the baseplate arm connection in both rotation and bending a larger baseplate a detachable electronics box and landing g
27. ion During development a Nexus 7 with a resolution of 1080x1920 was used but the app will work on resolutions significantly lower as well A screenshot of the ground station can be seen below 9 Y m 10 08 WTD Ground Station FLIGHT LOCATE CALCULATE FLIGHT PATH Figure 9 Screenshot of the ground station s flight screen 20 The ground station contains three tabs Flight Locate and Debug The Flight tab as shown in Figure 9 shows the progress of the flight process frequency input and a multi use button used to initiate the main phases The Locate tab once developed will contain a map displaying the estimated location of the tagged bat the location of the ground station and the heading of the ground station The Debug tab exists for development purposes as well as for manual control and troubleshooting The current implementation of the debug tab is shown in Figure 10 below WTD Ground Station FLIGHT LOCATE ARM PIXHAWK DISARM PIXHAWK START RECORDING STOP RECORDING THROTTLE LOW THROTTLE HIGH QUIT PING HOVER MODE TRANSFER DATA COPY TO USB Figure 10 Screenshot of the ground station s debug screen All three components communicate with one another with the Raspberry Pi being the main hub as it is connected to the Pixhawk and the ground station but these two components are not connected to each other An overview of this communication method and its different states can be seen in Figure 1 of Ap
28. ion regarding this task It has given us a greater understanding of how frequencies differ in regards to different devices and their merits The information acquired from this site has been a major contribution to our preliminary research on efficient methods used to track bats The site categorizes different transmitters based on current attachment method weight in grams life expectancy in weeks and antenna type These devices are currently used by researchers of various disciplines such as biologists scientific researchers and conservationists There is a practical description that explains in detail for our current transmitter LB 2X how differing temperatures can affect the transmitter based on the interval between pulses 5 Another source of information was Dr David Dalton who works for Photometrics in Tucson Arizona He aided us in deciding what type of antenna would be best for directional tracking He also gave us some advice regarding various methods for tracking bats 6 We investigated various metals to suit our requirements and constraints and examined how they compared in aspects such as conductivity density permittivity and permeability It was discovered that pure aluminum Al provided the strongest attributes for receiving the most reliable signal and would be lightweight and durable enough for our clients rugged terrain 7 5 DESIGN DECISIONS AND ANALYSIS Over the course of this project all three teams have
29. lti Rotor Outrunn HobbyKingS Compact 30A Watt Meter and Power Analyzer Shipping Hard High Strength 7075 Aluminum 0 125 Thick 8 by8 Multipurpose 6061 Aluminum Rectangular Tube 1 16 W Shipping Mach Screw 32x1 1 2 tax Home organizer box tax bolt nut and screw mis box amp bulk 4 invoices bolt nut and screw mis box amp bulk 4 invoices hard high strength 7075 Aluminum 09 thick 12 x12 Multipurose 6061 Aluminum Rectangular Tube 1 16 wall Multipurose 6061 Aluminum Rectangular Tube 1 16 wall Quick release button zinc plated steel quick release button connectors Frim grayf3 felt shee 1 8 Thick 12 x 12 adhesive back shipping Figure C3 Mechanical Final Expense Report 1 18 029 9 94 0 89 9 33 13 82 38 68 9 82 9 02 4 08 13 51 47 Raspberry Pi 3DR Pixhawk 199 99 3DR uBlox GPS with compass kit 79 99 Shipping Canakit Raspberry Pi B Ultimate starter kit USB Bluetooth adapt Azio BTD V201 USB Micro Bluetooth Adapter Class 1 Bullet connectors RC controller Pixhawk ESC Power connectors Programming tool Tax Encoder shipping Card W adapter 45MB s tax Shpping 5000 amph 3 cel battery USB extension cable tax gold blt conn male amp female 3 5mm Receiver mode 1 v2 firmware shipping ESC 20 amp with Simonk XT60 connector male amp female shipping ESC Progamming Tool shipping Figure C4 Avionics Final Expense Report 48 49 D
30. m which this tone is loudest the user is directed towards the transmitter and or other devices in operation in the same frequency band The requirements we are observing are as follows frequency range of 148 xxx 152 xxx MHz lightweight and Raspberry Pi B compatible The receiver must also be able to function without direct contact with the operator since it will be mounted on a flying drone 26 Currently our client is using an R 1000 receiver for wildlife telemetry However this particular model is not ideal for use on a drone due to its lack of auto adjusting gain or any sort of output besides raw audio data The R 1000 receiver is shown in Figure 18 below Figure 18 R 1000 telemetry receiver 11 We used the R 1000 in our design due to budget constraints but it must be stressed that doing so introduces its own problems The R 1000 is clearly a handheld design and not optimized for a drone With this design the user is intended to manually adjust the gain as necessary during tracking which is not possible while the receiver is mounted on the drone As aresult the additional noise introduced by leaving the gain at a higher than necessary value must be later dealt with by extensive filtering In addition to even capture audio data in a usable format a 3 5mm to USB adapter is necessary to connect the R 1000 to the Raspberry Pi which introduces its own interference To avoid all of the issues discussed above we strongly recom
31. mend that a receiver better suited to this design is added in the future One example of such a receiver that we found appropriate is the Lotek Biotracker shown in Figure 19 below It is waterproof works in a 27 wider range of frequencies 138 174 MHz compact and light especially if powered by our on board battery rather than the included battery pack Figure 19 Lotek Biotracker receiver 12 5 3 6 Filtering Regardless of the antenna and receiver configuration there will be some form of noise and or interference introduced to the telemetry system This noise will be increased by factors such as e Components operating at an interfering frequency Pixhawk Raspberry Pi even the battery to some extent e Components that act as antennae any unshielded wire or conductive plate e Objects between the telemetry system and the targeted transmitter trees rocks buildings etc Reducing noise and interference was a central goal of this project and the primary reason we used a drone for our design as the third listed factor can be mostly eliminated by flying above the treeline However despite our best efforts some noise remains in our received signal This issue was amplified by the fact that due to budget constraints we used an analog receiver with an adapter forcing us to work with raw audio data that is full of Gaussian noise 28 To combat these issues we created a Butterworth band pass filter which filters out
32. most expensive aspect of the project However the receiver that we found best for this project ended up being too expensive for our budget costing about 2 400 As a result we decided to work with a receiver given to us by the NAUFD which made the telemetry team s budget miniscule in comparison A comparison between the estimated and final budget for each subteam can be found in Figure 6 of Appendix C 30 7 CONCLUSION RESULTS AND THE FUTURE At the conclusion of this project a functional prototype has been created which fulfills the following specifications e Takes off and land vertically at the same point within an area of 5 m e Easily fits in a hiking backpack approximately 50x30x30 cm e Can sustain a drop of five feet while keeping systems operational and breaking only predicted replaceable failure pieces e Complies with FCC Federal Communication Commission and FAA Federal Aviation Administration regulations e Accurately outputs a signal amplitude and GPS pairing according to telemetry data e Allows signal and direction data to be transferred to an external device e Allows for manual override of autonomous flight systems The fully assembled final drone can be seen in Figure 22 below Figure 22 Completed wildlife telemetry drone 31 This system can fly vertically into the air spin 360 degrees while recording telemetry data and GPS coordinates and offload that data to an external computer for filtering
33. nown as NuttX and whichever flight control firmware is necessary For our purposes it is loaded with ArduCopter a subset of ArduPilot The firmware is configurable through one of two available mission planner software packages Mission Planner or APM Planner We found APM Planner to be more effective for this project as it is more straightforward to use and available for Linux and Mac OS X whereas Mission Planner is only available for Windows The Pixhawk and its various ports can be seen in Figure 7 below Spectrum Satellite Receiver Motor Safety Switch Aux PWMs Telemetry Radio gt Main ESC PWMs External USB MultiColor LED 12C Serial amp External Magnetometer 6 6 volt Analog Input Figure 7 Pixhawk flight controller 8 18 5 2 2 Raspberry Pi The Raspberry Pi is a single board computer with an ARM processor Our Raspberry Pi is version 6 as opposed to the common version 7 found in smartphones for the previous five years Its processor isn t especially quick but has been sufficient for this project and should continue to be in the future Currently three of the four USB ports are in use by the audio adapter Wi Fi dongle and Pixhawk The Raspberry Pi and its inputs can be seen in Figure 8 below 40 Pin GPIO Header Broadcom BCM 2835 amp 512MB RAM S Quad USB Ports 10 100 BaseT a Ethernet Socket A a es al el EE DSI Display mined hi AAA Micro SD Card Slot e on underside
34. ns for element lengths and spacing ccoococnnoccconccncooncncnoncnonanacinnnccinnnnos 24 Figure 17 Final antenna in its collapsed backpackable forM oooooonnnocccnnccccnonccinncccnnnnnos 25 Figure 18 R 1000 telemetry receiver vasija 26 Figure 19 Lotek Biotracker receiver i522 oa Nees peed Wola eden 27 Figure 20 Signal data before filtering eseeeseseeseeeesessseeseessrserssressrseresresseseresresseseresresse 28 Figure 21 Signal data after Butterworth filter eeeeeseeeseeeeeseeeseseessrseresressereresresseseresresse 28 Figure 22 Completed wildlife telemetry drone ooncononccnnonnocnconacconnconononnnonnnconrnconanonnnons 30 Figure 23 Filter signal data plotted with respect to tiM8 oooonnoccnoconoccconcnnonnnonncnonccnnncnnn non 31 Figure 24 MATLAB output of magnitude and time data 0 ee eee eseceneceeeeeeeeeeneees 31 Figure Al Figure A2 Figure A3 Figure A4 Figure B1 Figure Cl Figure C2 Figure C3 Figure C4 Figure C5 Figure C6 Side view of control volume with actuator disk at location of bold line 34 Blade strip co rdinate ti its 36 Propeller disc viewed from above oooooconococonocccooncccnoncnononanonnnnncnnnncononcconnnccnnnos 36 Blade element flow conditions and forces coooocnoccnonccnnnnnooncnonannnnnnnn cono ncnonccnnnos 36 State Machine for Drone Control Systems ooococcooccccoocccooncnononcnononccnnnnccnannnnnn 44 Estimated BUE A a A A das 45 Punding CONMIBUHONS A A OE 46 Me
35. oduced can be found using conservation of momentum in the form of Reynolds Transport Theorem considering some section of the stream tube which through our assumptions simplifies to T mv MV where ve and Vg are the velocities at the exit and inlet respectively Under our assumptions the mass flow rate is constant and equivalent between any two locations in the stream tube We evaluate the mass flow rate at the location of the actuator disk introducing a new term v which is the velocity induced at the actuator disk which results from the work input there Using this the mass flow rate is m pv A where A is the area of the actuator disk or the area of the circular plane in which the propeller spins This yields T pv A ve vo 35 The thrust produced by the actuator disk can also be modeled as T Ap A Where Ap is the change in total pressure across the actuator disk At this point it is important to note that work is being done on the air flowing through the actuator disk which results in an increase in kinetic energy of the flow Because work is done to the flow Bernoulli s theorem cannot be used to describe the flow through the disk only on either side separately Applying Bernoulli s theorem on the flow upstream and downstream of the disk respectively we find 1 2 1 2 p 5pvo P 5pvi and a Des p gt 3PV Ap p 5 pve Note Ap which comes due to the work done on the flow through the disk Simplifying
36. of the propeller This allows us to simplify our dC equation for a single blade to 1 dCr 5 oer dr Which we may integrate to get 1 1 Cr 30 Cr dr 2 Jo Similarly we can find 1c 3 dCo zap et Cp r dr Which our solidity factor is also useful for and may be integrated as well 1 1 Co Tal PC Cp r dr 0 This result can be simplified using A to get 1 1 Co zaf AG Cpr dr 0 Assuming a symmetric airfoil shape C can be found with Ci a a Where is angle of attack and a is the constant lift curve slope a 27 is generally a very good approximation for airfoils however the book here recommends a 5 7 which in this case results in C a 9 39 Note that this assumes a symmetric airfoil shape which will most likely under approximate the thrust produced Substituting this into our Cr integral we get 1 1 C 500 Or Ar dr 2 Jo Which evaluates to 1 0 1 a T e 3 2 So far we have assumed 0 and J to be constants This assumption however is poor Let us consider the differential form of the equation for dC and a differential form of the thrust equation found from momentum theory dT 2pv7dA Which can be nondimensionalized to dCy 44 r dr When we set the two equal to one another we find a quadratic equation for A whose solution is a function of r as given below OED Vitae 16 oa To more closely meet this assumption we vary 0 along the span of the blade By introducing
37. on The angle the velocity vector is tilted by the downward velocity is called We can see that E a Yit go tan Oy U 2 coso 1 dL 7 pU cli dy 1 dD z pU cl dy dT dL cos dD sing dQ dL sing dD cosh y Noting that V is the vehicle s vertical velocity Generally is assumed to be small and so we continue using small angle approximations aT dL dQ pdL dD y At this point it is convenient to nondimensionalize our terms We begin with r which can be seen to be a percentage of the radius R of the blade y r R This also arises as the result when we nondimensionalize the velocity U with the tip velocity OR U Qy OR OR Now we find a differential coefficient of thrust dCy and differential coefficient of torque dC dT 7 PAOR dQ dco TACQRYER We may also use tip velocity to nondimensionalize the induced velocity through the plane of the propeller vi Ve witV QY a lar OR ay OR 38 For simplicity we will continue our analysis for the hover condition where V 0 therefore pes et QR If we substitute the quantity previously determined for dT into our equation for dC we find 5 pUcC dy dro GRI ORY Which simplifies to It is convenient to introduce a new term called the solidity factor defined as NcR Nc AR TR Where N is the total number of blades This means can be seen as the ratio between the total blade area and the disk area
38. ould not be possible to send someone into the field with this drone with no training at all It is important that one understands these regulations and how to manually override the drone if an issue comes up Therefore we ve foregone this specification but decided to include a user manual with the drone The last of these specifications a battery breakaway to disconnect the battery after a fall of five feet or greater proved to be a project in itself that would take more time than we were willing to allot to it given our more pressing priorities with this drone We found that no off the shelf designs exist for releasing a battery of the size we used upon impact and that existing drone designs do not use such a mechanism We also found that the most pressing concern for lithium polymer battery safety is to avoid punctures and we ve taken appropriate measures to protect the battery which will be outlined in the mechanical design section of the report 3 DESIGN TEAM OBJECTIVES AND DELIVERABLES The team determined that breaking into three subgroups would be the most effective means of completing this project The three subgroups were decided to be Mechanical Avionics and Telemetry The tasks and goals for each of these teams are outlined below 3 1 Mechanical Create a frame capable of carrying needed payload and surviving a crash Design a propulsion system capable of lifting payload Build an antenna to telemetry team s specifi
39. ouple of undetailed example programs The library it seems was meant to provide control to humans rather than assist an autonomous search as we will do A second major source has been the community edited and 3DRobotics funded ArduPilot wiki a wiki for the open source flight control software at the core of the Pixhawk flight controller 2 The wiki contains information for similar but far from identical processes Should we need to modify the Pixhawk itself this wiki will be our greatest resource Finally a personal project of a published computer scientist and electrical engineer William Premerlani GE known as MatrixPilot has proven to be useful 3 It s a MAVlink capable autopilot comparable to the system on the Pixhawk but MatrixPilot s GitHub repository is remarkably well documented including how an autopilot handles MAVlink from its point of view We ve also included a source that discusses practical electromagnetic shielding for use in the event that our motors cause interference with the telemetry equipment of the drone 4 4 3 Telemetry Biotelemetry is the term used to describe techniques that incorporate the instrumental gain of a transmitter and receiver to transmit information from a living organism e g bats and its surrounding environmental factors to a remote observer e g NAUFD biologists In our research we came across a website which is hosted by Holohil Systems Ltd which has a plethora of informat
40. pendix B 21 5 3 Telemetry After an early consultation with Dr David Dalton we found that his team uses three different antenna styles in conjunction which are two three and five element Yagi antennae Dr Dalton s reasoning was that doing so provides a more predictable location of the bats Figure 11 below illustrates the differences between the gains of the different antennae Adding more elements will proportionally narrow and lengthen the beam width which produces a more accurate reading during triangulation BEAM 3 ELEMENT BEAM 5 ELEMENT BEAM Figure 11 Antenna gain comparison 10 5 3 1 H Element Antenna or Two Element Yagi The two element Yagi antenna is the smallest amongst the numerous Yagi element derivations This type of antenna is significantly lighter in weight and smaller in size when compared to other Yagi antennae but it lacks capabilities of receiving long distance signals Figure 12 below shows the configuration and azimuth plot angular measurement in a spherical coordinate system for this antenna The azimuth plot displays the beam width and length of the antenna s reception 22 27 551 Azimuth Plot L 0 0 deg Elevation Angle 6 26 431 0 0 dBmax Sice Max Gan 826 dBi Q Az Angle 0 0 deg FrontiBack 11 394 Beamwidth ce Siseiobe Gain Front Sidelobe 365 225 7 24 3 deg x 1 Az Angie 180 0 des 0 DD Figure 12 H element Yagi antenna with azimuth plot 5 3
41. pments and iterations of the wildlife telemetry drone Sincerely Wildlife Telemetry Drone Team ii Table of Contents in A apes heh te Ai at cee cat Nese ceed col hl re aie de hat oa Sek es Bi ana 1 De ey E CULICALLONS nns in nna iria is 2 3 Design Team Objectives and Deer able 4 A A Getto A a E od AA E A A ER AN a 4 Died AVONS A ale e A ea te aed RR 4 EAE RE TEE Ys coat A E E E 5 4 Initial Restarch tina la esaa ISE NR a Eats 6 4 1 Mechanical iss ai oca dd nd il oe o ad e eden 6 42 AVIONICS O UI EEEE E teeta ae ale Uae eae 6 4 3 MOVING A n baits acadde aes alte tari bonlye ded anes a a 7 5 Design Decisions and Analysis a o 8 Sul Meca li A ie AA i a BA a Ad E ii 8 i bal 0IL eT ET a o EAE E EE E E AEE E 8 5 1 2 Thrust Calculations ninaa a eel et e aaa A R TES 9 A E E urn eer A ES 10 51 4 Landing Gea eunis n lla sandals E Ea hee 14 5 1 5 B ttery BreakaWa V se ie erte a E tiee E iaeoe raa gesa 14 5 2 AVIONICS Sa A tere eds 15 A A 17 3 22 On board A dt a OS 18 52 3 Ground AA A A ee ete 18 A EN 21 5 3 1 H Element Antenna or Two Element Yagi oooocnnncnnoninonnconcnnonnnonncnoncnnnncnnnnno 21 5 3 2 Three Element Yagi Antenna AA A duea aap bobadetey anndaanemecaanigeee 22 5 3 3 Five Element Yagi Amtenina 53 035 55232 ccsaatssassacssateccads cocinan dascaedeseseadeeabedantacone 23 5 34 Final AMENA it 23 5 3 5 RECEIVED A recess 25 A a a e et a eo E oes dacs 27 iii 6 Itemized Budget 7 Conclusion Results and th
42. spberry Pi is accomplished through a serial communication protocol known as MAVLink MAVLink has not yet matured and is not well documented However some relevant information can be found in the drone s internal documentation which should be all a developer will need to continue this project Although the communication is currently performed through USB 2 0 UART is also a possible option through the Pi s GPIO pins and the TELEM 2 port on the Pixhawk It s recommended that UART only be used in the case that additional USB ports are required for future purposes Through MAVLink the Pi receives sensor data sets flight paths and performs other functions The flight paths are calculated relative to the drone s position at launch and are sent to the Pixhawk as mission items using the same method as the mission planner programs The Pixhawk however has a priority system in place that prefers RC controller input to serial 17 communication This is important to the last component of the avionics system the RC controller A relatively long range RC controller is included for manual flight but is only necessary in emergency cases and for meeting FAA requirements Assuming no failures it will not be used outside of manual testing but users must be able to operate it nonetheless 5 2 1 Pixhawk The Pixhawk is our flight controller In terms of processing power it s comparable to a Raspberry Pi but runs a barebones operating system k
43. tates while collecting signal data then lands and sends the data to a separate computing device to be processed into a latitude and longitude location where the bats are likely to be found At this time a functional prototype has been created which can fly vertically into the air record telemetry data and offload that data to an external computer for filtering and display A manual override is in place to ensure user control at all times and a ground station application has been created to control all basic functions of the drone The drone is backpackable and can sustain drops of at least five feet with only field repairable damage We feel that these results watrant a continuation of the project as this design has proven that it can work but is not yet in a state that would make sense for researchers to use The drone would benefit from a number of improvements in frame construction wireless communication receiver capability and general ease of use before deployment in the field This report explains what was used in the drone and why it was used while providing details of the analysis undergone how specifications were met an overview of the projected and final budget and a summary of work for the future In addition to this report we ve created an owner s manual and extensive documentation for future teams to continue work on the drone We re proud to present the results of this project and we look forward to seeing future develo
44. three element antenna This provides us the capability of adequate signal range and therefore a more precise location when utilizing triangulation while lessening the payload and in turn increasing flight time With this in mind we created the antenna shown in Figure 15 below in collaboration with the mechanical team who ensured that it is durable collapsible lightweight and includes predictable failure points for easy repair in the event of a crash 24 Figure 15 Final antenna modelled in CAD This design uses a carbon fiber boom to lighten the antenna while still providing a rigid attachment point and 5 8 copper tubing for the elements The spacing and element lengths were derived from the equations shown in Figure 16 below DRIVEN ELEMENT S1 4 S2 gt DIRECTOR REFLECTOR Element lengths Director Driven clement Reflector Spacing 40 7 Director Mite 5 7 DE 1 F Mita Reflector 159 Milz 43 29 Spacing Fu Figure 16 Equations for element lengths and spacing The antenna is also collapsible The antenna in its disassembled form can be seen in Figure 17 below 25 Figure 17 Final antenna in its collapsed backpackable form 5 3 5 Receiver A receiver is a device that is able to hone in on different frequencies and provide the user with a tone when it senses the desired frequency By aligning themselves with the direction fro
45. ting and sbattery voltage to output graph of thrust as a function of power Sconstants rho 1 kg m 3 air density a D 7 lift curve slope N 2 snumber of blades c 08 D sassumed chord length as a percentage of diameter B 85 sassumed percent of blade span producing lift tw pi 9 Slinear twist slope based on a 10 diameter prop with 10deg pitch angle at tip and 30deg pitch angle at root s nit conversions D 0254 D Sm M 0254 M Sm c 0254 c Sm Coeff of thrust CT 3 2 sqrt 2 sqrt 9 8 12 pi D B atan 4 M 3 pi D 9 pi D B 1 B tw N c a N c a B 6 pix D 2 sCoeff of power CP 1 25 4 B 3 1 15 sqrt 2 CT 3 2 Sincludes a fudge factor of SCP 4 7 3 1 15 sqrt 23 C1 3 2 Possible rpm range of motor F 0 100 KV V Om 2 pi 60 F ole pm a rad s o T CT pi rho D 4 16 Om 2 SN P CP rho pi D 5 32 Om 3 SW sunit conversions T 22481 T Slbs ST T 9 81 skg plot P T end 43 SPropTest m Script to run prop function and compare to presented data SWritten by Alex Moore Slast revision 11 6 14 Sinput data provided online from hobbyking com for NTM multirotor motors data 8 4 800 22 2 310 1 11 8 4 900 14 8 159 0 75 8 4 1100 11 1 100 0 54 8 4 1100 14 8 116 0 82 9 6 900 1 1 1 120 0 68 9 6 900 14 8 234 1 05 9 6 1100 Ted 149 0 73 9 6 1100 14 8 285 1
46. v 21 2014 11 Comunications Specialists R 1000 Telemetry Handheld Receiver Internet http www awt co za awt_accessories accessories htm Nov 21 2014 12 Biotracker Internet http www lotek com biotracker pdf Nov 21 2014 13 J Seddon S Newman Basic Helicopter Aerodynamics 2nd ed Reston VA AIAA 2001 34 APPENDIX A THRUST ANALYSIS The essential function of a propeller is to convert a shaft work input to a change in momentum for a stream of air which in turn applies a force to some body In the case of a quadcopter style drone this thrust force is the means of producing lift to achieve flight Understanding the principles for achieving thrust then is essential to selection of suitable components to achieve flight The following is heavily sourced from Basic Helicopter Aerodynamics Second Edition by J Seddon and Simon Newman from the AIAA Education series It is adapted to the specific application of power and thrust calculation for hobby propellers designed for remote control vehicles To begin modeling thrust from a propeller let us begin by modeling the propeller itself as an actuator disk which a stream tube of air is passed through We will assume incompressible steady flow with uniform properties at the inlet and exit We will also neglect gravitational effects VetVi VotV gt Figure 1 Side view of control volume with actuator disk at location of bold line 13 The thrust pr
47. ve a tighter fit to the failure pieces in preventing rotation and therefore were used in the final frame design The combination of nylon connections in the vertical and horizontal planes allowed the arm to disconnect from the baseplate upon a crash regardless of the direction of the impact The failure of these pieces protects other more expensive or less field repairable pieces Therefore having these pieces allows the drone to survive a 5 foot drop with only field repairable damages as specified by the client The operator of the drone in the field needs only to carry spare nylon bolts and button connectors in case of a crash 13 The final frame design uses a larger baseplate at 11x11 so that the electronics can more easily fit on the drone This design choice was made after realizing that the prototype baseplate of 8x8 was too small to fit an impact resistant box for the electronics The detachable box was chosen because it met the size constraints and could fit all electronics in it It was chosen to have Velcro to attach the electronics box to the baseplate because it would make the drone more collapsible and it allows the electronics to stay completely connected with the exception of disconnecting the ESCs This makes the drone more user friendly because the operator does not need to reconnect any complicated electronics One inch thick foam padding was used to pad the interior of the box to protect all electronics housed within
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