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Design of a Remote Person View System for a

1. Figure 7 6 Banking of 39 with no image distortion attributed to the coding of the MinimOSD since the same happened in Section 6 2 where fast movements were tested with and without the MinimOSD eed ss A aes swb la oz 41224 MH Figure 7 7 Distortion due to transmission through the MinimOSD Finally on another flight it was tested the importance of the video antenna direction since it had such a wide opening 60 when compared with the Yagi The UAV was flown nearly parallel to the GCS it was doing almost 180 with the helical direction and the result was the video was very disturbed see Fig 7 8 Regarding the use of the camera gimbal it can be said that it has a great potential depending on 70 Figure 7 8 UAV flown in the direction of the GCS doing 180 with the Heliaxial orientation how it is used During flight two modes were experimented one that used the gimbal to stabilise the image and another that enabled the gimbal to be used only in manual mode The gimbal stabilisation test did not retrieve positive results Despite working properly it just turned the flight confusing to the pilot through the screen Figure 7 9 a exemplifies how a simple pitch manoeuvre would totally block the view making it dangerous The manual mode of the camera gimbal on the other hand turned out to be a useful feature This way the pilot was able to recognise the field and its current position with pitching down Fig
2. e Transportation In a situation where a non profit organisation manages to stockpile medicine for people in remote African villages but cannot get to the remote areas fast enough to save lives UAVs can make all the difference An example is Matternet a company that is building a network for drone based deliveries to remote areas 8 Figure 1 2 UAVs wildfire aiding 7 1 2 State of the Art Nyquist 9 describes a project developed by the Oak Ridge National Laboratory that made use of a radio controlled aircraft that was modified to carry a 35 mm video camera and transmitter The system was designed to collect aerial photography for environmental site characterisation and management update aerial photos of solid waste storage areas and document construction activities Quilter and Anderson 10 mounted a 35 mm camera in a model aircraft to obtain low altitude large scale photography to document stream and riparian restoration projects In 2002 Stanley Herwitz professor of Earth Sciences at Clark University Worcester was awarded a NASA grant to fund the UAV Coffee Project 11 The project deployed the UAV Pathfinder Plus to collect high resolution multi spectral imagery to evaluate coffee bean ripeness In 2003 Simpson et al 12 designed a remote person view RPV that featured a modified com mercially available model sailplane by installing a Jeti Phasor electric motor a Opto speed controller and 12 cell 2400 mAh batt
3. 2 2 2 UAV Flying Legislation A quick research in local newspapers lead to the conclusion that the Portuguese government is yet to build a clear law on UAVs However in later months that empty space has been reduced by the Instituto Nacional de Aviac o Civil INAC by proposing a law in that sense The use of any UAV would depend on the authorization of INAC limiting its access to the segregated aerial space so that UAVs are not used in near the normalized aerial traffic This discussion on the regulation of UAV flights was first presented in 20 2 3 RPV System Requirements The airframe and components chosen will have to take in consideration a set of requirements Some of the requirements can be derived from Section 1 3 e The weight of the vehicle must be as low as possible to allow an efficient flight and small vehicle size and to allow operation in very small airfields Also it should be able to carry a payload up to 1 kg e The airspeed in the cruise loiter phase of 8 hours should be about 7 m s 25 km h at an altitude of 1000 m e Develop a low cost small footprint electric UAV 10 The range of the RPV system must correspond to the 8 hours of flight meaning that at a speed of 25 km h with 4 hours for going and 4 more to come back the maximum distance between the ground Station and the aircraft will be 100 km Figure 2 4 represents an idea of the coverage that the UAS could provide in national territory er o
4. Attribution of frequencies by ANACOM a ee ee Comparison of phase noise and output power of long range transmitters Comparison of physical specifications for the long range system Comparison of physical specifications of autopilots 31 32 33 Comparison of autopilot functions 31 32 33 Emm nn General specifications of 3DR telemetry radio Frequency Spectrum up to 3000THZz 22 RC link range with both monopole and yagi antennas Kx 181 CCD Sony Camera characteristics 46 222222 222er Main Features of the OSDs considered the MinimOSD the RVOSD and the EZOSD ER AAA A A TA Oe See Advantages and disadvantages of different frequency bands Main specifications for each video system Rx and Tx 49 50 51 Connections between the APM and the Rx700 o Radio Calibration End Result o EEPROM parameters for the interaction between APM and MinimOSD Connections from the MinimOSD through the miniboard to the video TX Output behaviour of the servo in function with the distance Proposed Solutions for multipath fading propagation and polarization losses radiation pattern null and signal obstruction 66 Lo m mn Inclination wi
5. c Ranges in controlled environment and in flight tests Figure 8 1 Final configuration for long range flights In both systems directional antennas of high gain are used on the ground station to see that it is not necessary to spend to much energy in order to have a signal travelling long distances After proposing 1 the overall COTS systems several tests are conducted in order to do an estimate of the range and quality of the same In order to perform these tests parameters that best characterize each system are proposed For the characterization of the control system a straight forward parameter is used the RSSI provided through an analogue pin of the RC receiver is used to evaluate 2 different antenna configurations in a controlled environment As for video feed since through research it was concluded that retrieving the Signal to Noise Ratio SNR to have a unit of measure for the video range is not enough the same is characterized using a subjective method called Mean Opinion Score MOS which relies on the opinion of viewers to evaluate the image quality in terms of colours contrast borders movement continuity phenomena of flickering and smearing Other three issues that often occur in video transmissions are considered polarization loss antenna pattern null and signal obstruction 8 1 Achievements The major achievements of the present work can be summarized as follows e Design and setup of a video system
6. 7 9 b shows an example of that 8 38 821661 cd 9 18232 a He il i 0 0 O BJ nl Oo in I U En gt ES N ch io LO tI gt AA e ir nr F 714 al tal ID We so EM Lobos 10 Dar Wp a UAV climbing with the stabilise en b UAV recognising the field with man abled ual gimbal Figure 7 9 Camera gimbal operation modes In conclusion the camera gimbal has great potential when used manually The stabilisation will block the view for the pilot but manually it enables him to perform recognition 7 1 3 Overall Flight Quality In this short range flight the UAV went up to a maximum distance of 396 m and travelled a total of 4829 m spending only 1451 mAh 35 of the battery The UAV was considered a stable platform for a longer range Since it was proven in Chapter 6 that the UAV could handle both in video and control a flight with a maximum range of 8 km a flight with 2 km of maximum range was planned and its results are presented and analysed in the Section 7 2 71 7 2 Longer Range Flight Test The chosen date for this flight test was when weather conditions were once again favourable as speci fied in Table 7 2 Condition Value Wind Velocity km h 9 Gust km h 12 Direction East Temperature C 12 18 Humidity 20 Table 7 2 Weather conditions during the longer range flight test The flight test was again conducted at Pista de Aeromodelismo de Corroios which p
7. RPV station connection schematic Figures 5 9 show the final result for the UAS setup on the day of the first flight b Ground station Figure 5 9 Final result for the UAS setup on the day of the first flight 43 44 Chapter 6 Sub Systems Testing in Controlled Environment To certify the COTS products that were purchased black box testing was used Black box testing is the method used for certifying COTS equipment that is acquired The funda mental of this technique is to test the functionality of the component without any understanding of the internal structure of the component UAV flight operations are limited in range and endurance by the mission s essential communication link capabilities In this section it will be addressed the multiple fold problem of trading off in a set of mission re quirements balancing between the communications capabilities and the desired UAV radius of action The system will be first evaluated in a controlled environment in the sense that it is being hold by a person two meters above the ground in seven discrete positions where there is no risk to the UAV or the surroundings 6 1 Testing of the Radio Control Link Systems 6 1 1 Test Design The objective of this test is to evaluate the influence of the type of antenna in the control system range and also the influence of the output power in a single radio link configuration Figure 6 1 shows the two antenna configurations tha
8. power source and the Electronic Speed Controller ESC to power the servos and motor as seen in Fig C 2 from Appendix C a Direction of the APM with the air b APM attached with velcro to the airframe craft 64 Figure 5 2 Concerns about the mounting of the APM 5 1 2 Flight Controller Configuration Before using the APM it has to be configured first which is done through Mission Planner MP and for that there has to be a properly setup RC transmitter Tx and receiver Rx pair The configura tion process starts by uploading the latest firmware into the APM which in this case is the arduplane firmware The port assigned to the APM has to be Arduino Mega 2560 and the Baud rate set to 115200 38 Clicking on Connect button the MP will connect via MAVLink which is a protocol for communicating with small unmanned vehicle 29 Since the Skywalker is a standard airframe a pre made configuration file can be used 63 but there is still the need to configure it for the hardware in question which is done in MP with the button Calibrate Radio The results should then match Table 5 2 Channel PWM Low High Ch 1 Roll left Roll Right Ch 2 Pitch forward Pitch back Ch 3 Throttle down off Throttle up Ch 4 Yaw left Yaw right Ch 8 Manual Autopilot Table 5 2 Radio Calibration End Result Figure C 2 from Appendix C shows a detailed connection scheme of how the RC sub system was assembled 5 1 3 MinimOSD Se
9. when used with the appropriate antennas There are three main factors when selecting the video system 44 e Frequency e Output Power e Price Analogue wireless is the transmission of video and or audio signals using radio frequencies which can be found in 1 2 2 4 and 5 8 GHz as mentioned in Section 2 2 The COTS video systems market is offering a variety of light weight mobile UAV to stationary GCS options with a wide spectrum of frequency bands available However each frequency has its own advantages as well as disadvantages which are briefly summarised in Table 4 3 and so the 1 2 GHz frequency was chosen as a way to compromise long range with image quality since it will allow long distances with a fair video quality Frequency Band GHz Pros Cons Signal range Antenna size Penetration 3rd harmonic of LRS Less power consumption Clearer of interference 1 2 1 3 Expected interference in populated areas due to its wide use in Video and sound quality cordless phones and wireless LAN 2 4 Low cost system due to mass production Line of sight operational requirements Range affected by humidity in the air Legal transmitting power restrictions Interference with nearby RC systems Lowest Penetration Small transmitting antennas Lowest Range 58 Low distortions Severe multipath distortion causes very poor performance in FM mode Line of sight operational requirements range affected by humidity in the air Equipment expensiveness Tab
10. 10 a 0 a i 1 1 0 1 2 3 4 5 6 7 8 D 1 2 3 J 5 ia 7 E a Distance Km Distance Km a Changing output power on the Monopole antenna b Changing output power on the Yagi antenna Figure 6 4 Changing the output power and antennas of the transmission Figures 6 4 show the obtained values for RSSI which measures signal strength in percentage at a certain checkpoint for each antenna configuration Figure 6 4 a reports the evolution of the RSSI for the monopole antenna as a function of distance e Different output powers show similar results An output power of 0 5 W will handle the same range as the 2 W and spend less energy e The system handles a distance of at least 4 km Fig 6 4 b reports the evolution of the RSSI for the Yagi antenna as a function of distance e Different output powers show similar results until the 7 km checkpoint is reached At the 7 km checkpoint with 0 5 W the RSSI falls 10 points and no longer works at the last checkpoint e From 0 5 to 1 W the signal regains its strength With a distance of 8 km the RSSI is still strong and only decreased 10 from 1 km to 8 km Although the last checkpoint still has 40 signal strength the experiment ended due to lack of space as previously discussed e Between the 2 last checkpoints there is an increase in RSSI This is due to the directivity of the Yagi antenna Since the UAV was already out of sight it got harder to manually orient the antenna towards t
11. 11 Mes highy recommended that a high torque Standard size servo with a minimum torque of 45 inoz be used 12 Circuit requires two of the same RX modules be used for accurate RSS measurement and calibration 13 Blue wire is connected to the center pin of where the servo potentiometer was removed in the servo 14 Landing gear servos will not work Figure A 2 Antenna tracker layout 71 Figure A 3 shows Alexander Greve s own prototype a Up view b Front view Figure A 3 Alexander Greve s own prototype 71 89 90 Appendix B Airframe and Engine Testbed Selection B 1 Airframe Testbed Selection There are three types of fixed wing airframes the traditional sports glider or pusher and flying wing Their pros and cons are shown below A brief web research is enough to understand that there are lots of options available long endurance airframes have many reviews on what to look for and what not to get The second search was focused on what other people have done and what do they recommend Out of many 5 models in which all of them are fixed wing airframes stood out and were taken into account Their specifications are gathered in Table B 1 EPP FPV Skywalker X 8 Skywalker2013 Skywalker 2014 Skywarrior Fuselage length mm 1150 NA 1180 1300 1400 Wing Span mm 1800 2120 1900 1800 2030 Airframe Weight g 1000 3500 1300 1300 1800 Price 54 127 85 110 170 Table B 1 Main specification of the selected airfr
12. 3 36 10 48 Time min Figure 7 3 RSSI versus distance home Regarding the influence of the distance home for short ranges it is seen in Fig 7 3 that the point of maximum distance shows a level of RSSI of 82 The same figure shows that for short ranges the RSSI is not greatly influenced by distance It is also shown a lack of tendency for continuity meaning 68 the RSSI has inconstant readings and can only be seen as a reference since it can vary from 60 to 90 in short periods of time According to 3DR 70 it was found that the reason why this happened was maybe due to the fact that while in the air measuring signal strength becomes a difficult task because of radio and magnetic interference from external factors such as wireless networks television antennas etc Antennas on receivers catch all of this different radio signals all the time Having other sources of the same frequency will affect measures Figure 7 2 shows three distinct pin points These pins represent periods where the UAV went out of the Yagi s directivity limit which is 30 and with the help of Fig 7 3 it is possible to see that even in a short range the directivity of the Yagi is important In pin 1 the RSSI is at an average of 70 at a distance of 300 m in pin 2 the RSSI is stronger that in 1 but it is still noticeable its decrease to an average of 75 The same goes for pin 3 with an average of 65 As for the influence of banking manoeuvres on the RSSI show
13. 31 32 33 34 34 37 37 37 38 39 41 42 42 42 7 6 5 1 Test Design 6 5 2 Test Results Flight Testing TA SNO Range Fight TEST se opcion ime e e ee an ed ar ae fil RC Dink Quali sites reeadce ce 6224 be SAA SES es SSS ES Ria Video WINK QUAY rocas amara oe Ss ot ae ews E 7 1 3 Overall RiantQUAy 524 ae a E ao SO SE Sarees 7 2 Longer Range Flight Test o 7 2 RO AA A ee DR ee fee Nideo Link Quality iba Se a eo AA T23 Overall Flight Quality 2 lt lt 2425228 Ade EB BER CES E DE SSS Final Considerations 8 1 Achievements 8 2 Future Work Bibliography A Design of an Antenna Tra A 1 Problem Statement A 2 Long Range Design Airframe and Engine Test cker bed Selection B 1 Airframe Testbed Selection 0 0 0 ee ee a a aa B 1 1 Weight Distribution 00 u ai ws a wl at we a Row a ew aE A B 2 Electric Motor and Propeller Testbed Selection 0 2 000000 B 2 1 Propeller B 2 2 Electric Motor Sub systems Schematics xiii 67 67 68 69 71 2 2 73 76 77 78 19 85 87 87 88 91 91 92 94 94 94 99 XIV List of Tables 2 1 2 2 2 3 3 1 3 2 3 3 3 4 3 5 3 6 3 4 1 4 2 4 3 4 4 9 1 9 2 9 3 9 4 6 1 6 2 6 3 6 4 6 5 6 6 6 6 8 Airborne equipment necessary for RPV operations Ground station equipment necessary for RPV operations
14. RPV due to its small size and low light capability Plus electrical wiring is exceedingly simple which is 3 wire outputs ground power and video signal output Some may have an additional wire for analogue audio output if the camera also has a built in microphone Most cameras are designed to operate within a specific voltage range which is usually between 6 to 15 V making all RPV electrical components to operate with 2S and 3S LiPo packs without the need of voltage regulation which is usually is made without great efficiency by losing energy in the form of heat 42 43 When choosing the RPV camera there are two primary variables to consider and three secondary more 44 e Image device type e Analogue video encoding type e Size e Field of view e Image definition Regarding camera imaging device there are CCD or CMOS which stands for Charger Coupling Device and Complementary Metal Oxide Semiconductor respectively Typically CCD type cameras have better low light and high light level performance meaning it will not go blind when pointing the camera into or near the sun and are also less susceptible to cause image wobble lts disadvantages are weighting more being bigger and more expensive and consuming more power when compared to the CMOS type 45 About the camera video encoding type either NTSC National Television System Committee or PAL Phase Alternating Line is generally not an important decision because most RPV co
15. System 7 2 1 Description of UAV SYSTEMS us e a ep 2 2 2 a E ala wR A 7 2 1 ADONG dd ra AA di A a Ma and dd 7 2 1 2 Ground Station s 4 4 4 2 amaid 00 a n esd comme a hoa ee 9 ae ESGISIALUON ana Bh ans a A A ie te SCE we oye dede de E Ba ee 10 2 2 1 Bandwidth Legislation 22 2 2 Hu m nn 10 2 2 2 UAV Flying Legislation sssr s 3 28 A aoe amp Shwe RD BW Ga ee ee we 10 2 3 RPV System Requirements 2 22 2 2 Cm m 0 a 10 3 Design of Control System 13 3 1 Radio Eontr l Sysiem ss ara we usa ete abe Boe oe a aan Eee 14 3 1 1 Remote Control Transmitter ee 15 Sole WACCOIVEL 44 de aida o a RE A ees 16 3 1 3 Long Range System LRS e 16 3 2 PUONE CONTO a a A ARABE A a a SS 18 3 3 Telemetry Radio e r sa 3 2 a A RARA 20 xl 3 4 Radio Control Antennas HH 3 4 1 Tx Antenna Testbed Selection 2 HH a nn 3 4 2 Rx Antenna Testbed Selection a a a a a a a 3 5 Estimation for the Communication Link Systems aooaa aaa a a a a Design of Video System 4 1 Remote Person View Setup a a a a a dll Camela a Eh oe tae DD RS ae BS aaa Ge es 4 1 2 On Screen Display 2 22 2 m nn nn 4 1 3 Video Transmitter and Receiver a eee eee eee 4 1 4 Video Feed Antennas ce 4 1 5 Video Display su Geko ost te ara aw 0 a Bow oe wh A oe ee VA 41 65 Video RECORdeR amp 5 0 Siok WS Seah a MG ee dv Ae a CS 4 2 Propagation Aspe
16. Yagi is reoriented and as soon as this happens the link raises its strength to 86 In conclusion although the RSSI is influenced by propagation loss the parameter that most affected this flight was the directivity of the antenna the same happened to the video link Also comparing the performance of this link with the performance on the ground it can be said that this system can top a range of at least 7 km 7 2 2 Video Link Quality As done for the short range flight the 2200 m flight is also analysed in terms of video issues and quality Just as it was done with the Yagi not to take any risks the Helical antenna was hand oriented so that those issues could be minimized The flight path is shown in Fig 7 10 In the same figure are marks that represent issues from the video link that were found to be noteworthy 13 a UAS performing a banking ma b Obstructed heliaxial antenna noeuver Figure 7 12 First pinpoint 1 remarks In the first pinpoint 1 two situations were tested the polarization loss issue seen in Fig 7 12 a and obstruction in Fig 7 12 b The polarization loss was tested by making a banking manoeuvre with a roll angle of 53 from the same figure the sky can be considered as very gray this is due to the direct exposure of the camera lens to sun light and the result was positive for the circularly polarized configuration since there are no interferences of any kind As for the obstruction i
17. allows an estimation for the base drag coefficient Aerodynamic Specs Vetimb 10 2 c m 0 22 V 1 77 1075 Rex 1 267 10 Cf 0 0068 x C 0 4 t cmax 0 13 A cmax deg 1 47 F 1 55 Swet S 2 044 Up 0 022 Table B 4 Intermediate steps for calculation the Base Drag Coefficient Available Motors Every required parameter is now computed and so it is possible to estimate the required Thrust T 8 11 N and Power P 82 7 W From the above estimate for the thrust and maximum power an OS3810 1050 engine with specifications given in Table B 5 was chosen OS motor 3810 1050 Volts 12 6 KV rpm V 1050 Weight g 102 ESC 50A Battery 3S Prop 9x6E Max Thrust kg 1 3 Max Power W 315 Table B 5 os3810specs Although it was estimated the necessary output thrust of the propulsion system when tested in the field it did not seem to provide enough thrust since it turned out to be a day with some gusts although it allowed for minimum consumption in cruise a gust might become a problem This was done by holding the UAV by its wings as in Fig B 2 a and giving it maximum thrust Having bought the engine the size of the propeller limited by its diameter there was the option of raising the motor axis by building a support This would allow the use of blades with bigger diameters 96 The support was done using a CNC machine automation of machine tools that are operated by precisely programmed commands and a light composite
18. and better solution for Long Range Unmanned Air Systems The platform in question is a glider and is composed by three main systems the radio control the video feed and the telemetry radio that together connect the UAV to the ground station The parameter received signal strength indicator RSSI was used for control evaluation While propagation polarization and obstruction losses were used for evaluation of the video system Although the long range system encountered difficulties in reaching a maximum flight range it proved to be useful for long range applications Keywords RPV UAV long range video radio control Contents ACKmoWledgments asma aa AIR IE eee eee bee ee V RESUMO araa Gee See aoe Goh ee ee ee do ee Ma ee vii ADSMAC ense ate So dd bg is A date Bs ese ee SS tees a a nb Oe ae eee ae 4 ix LISCO TADOS inn a se E de Gres ee ae nia Se Ser ht ala dio da la rata Be oR Br Ge de Er eevee Xvi ISEORRIQUISS same dd ack os ae A A anal e vis Bs dls lc nes meer ee al Se Wh BL eel zer By xix Acronyms xxi Symbols xxiii 1 Introduction 1 lll MOIVALUON 8 mesie vet a o rio weg E As hee ae are Uae AE a ade a g 1 12 State ol ING ARE a os de o ie he ve oa dyes Sa e the Ga pie vee de Beth de a Tg de e de te de aria SS 2 o Ab oe veers sith pei ic pete ee ae ae ee Bigs OP Ge a oe Co AG on Sd ra cae ue 3 14 ODJECUVES lt assi i acd Boe EE ei a id 5 1 5 Structure of the Document nn 6 2 Description of the RPV
19. b it is stated in 52 that combined with a helical antenna at the receiving end it provides the desired long range more than 50 km at 1 2 GHz at a price of 35 Directividad 30 Dmax 2 30 dB i a Figure of the skew planar wheel antenna 6 Skew planar wheel antenna radiation pattern 3D Figure 4 4 Skew planar wheel SPW12 1200 1360 MHz Antenna 53 The chosen ground station antenna is thus a helical antenna sourced from Circular Wireless It is a circularly polarized directional antenna with a gain of 12 dBi and 60 of beamwidth see Fig 4 5 b ideal for use in long range flights 52 The helical antenna is priced at 82 Directividad 30 Dmaw 12 04 dB 1 a Figure of the helical antenna b Helical antenna radiation pattern 3D Figure 4 5 Helical 12 910 1680 MHz Antenna 54 4 1 5 Video Display For video display the Fieldview 1010 Fig 4 6 a was selected because it has an RCA input making it compatible with the video receiver and most importantly it does not switch to blue screen when the 33 signal gets weak which on the contrary would represent a high flight risk This display is priced at 165 o vie Fore a Fieldview 1010 Display Monitor 55 b DVR SD recorder 56 Figure 4 6 Recording and displaying devices 4 1 6 Video Recorder For video capture the selected hardware was the Hobbyking DVR SD card recorder Fig 4 6 b This recorde
20. best antenna configurations for video and RC the same was applied to a flight test in which its strengths and weaknesses were analysed 78 A maximum flight range of 2 2 km was reached Although the UAS seemed to handle a lot more than 2 km it was decided it was better for the UAS to return home because it was getting to hard to manually point the antennas towards the UAV as it got out of sight Extrapolating the UAS with a 3S LiPo battery on board can perform flights of 10 km distance and still have 25 of battery reserve which can is summarized in Table 8 1 c With that said it was proved in this dissertation that the system is suitable for distances of at least 8 km and that range Is limited by the fact that the ground station antennas are not directly pointed to the UAS as it gets harder to manually point them for distances that are out of the line of sight 8 2 Future Work There is however potential for enhancing the obtained results The major concern during flight testing was the orientation of the ground station antennas towards the UAS The use of an antenna tracker should be tested analysed and implemented the same way as the other systems were in this disserta tion In order to break barriers in terms of range and endurance a structure with concerns in aerodynamic performance should be implemented and also the use of solar panels that no longer makes energy an issue Also the use of the flight controller s autopilot fea
21. g ts ai Figure 2 4 UAS coverage assuming a 100 km range along the portuguese coast 11 12 Chapter 3 Design of Control System This chapter aims to describe the design of the control sub system used for this dissertation in which Commercial off the shelf COTS products are used this includes the primary components such as remote control transmitter long range radio receiver and high gain antennas Radio control RC is the use of radio signals to remotely control a device The term is used frequently to refer to the control of model vehicles from a hand held radio transmitter RC electronics have three essential elements 1 The transmitter is the controller that has control sticks triggers switches and dials at the pilot s finger tips 2 The receiver that is mounted in the model receives and processes the signal from the transmitter translating it into signals that are sent to the servos 3 The servos that are mechanical actuators that follow the commands sent by the transmitter and converted by the receiver In order to perform long endurance flights two add ons need to be considered e Flight Controller autopilot e Long Range System LRS While the former provides navigation and flight aids the latter extends the radio control range A block diagram of the entire RC unit is presented in Fig 3 1 Antenna Figure 3 1 Block diagram showing the radio control RC sub system 13 3 1 Radio Control System
22. hobbyists and other interested and skilled people have been coming up with all kinds of creative uses for unmanned aerial vehicles Until now drones have found applications in e Farming Fig 1 1 Farmers have an important but tough job and unmanned air vehicles UAV are a great way to do aerial surveys of crops so that farmers can see if their irrigation systems are working how their plantations are growing or even see if any plantation is affected by pests and diseases by using infra red sensory 2 e Sports Coverage UAVs are a great way of covering a sport event from above not only is it enter taining to watch but it also gives coaches a unique and valuable perspective on how their players are doing 3 Law enforcement Police departments use UAVs for surveillance and related activity and border patrolling 4 Environment All kinds of scientists are using UAVs to keep track of the environment for example to the United States Environmental Protection Agency EPA testing air quality 5 NASA is using UAVs to probe ozone loss and in Italy UAVs have been monitoring on illegal dumping for years 6 e Wildfire Control Fig 1 2 UAVs are becoming an incredibly useful tool for fire fighters especially those who have the seemingly impossible task of putting out wildfires The aircraft are used not only for spotting and gauging their movement but also actually fight fires while keeping the fire fighters away from harm 7
23. input a full 6 V can be sent to these receivers by connecting the battery to an unused channel or by using a Y harness to connect it to a channel in use by a servo 3 1 3 Long Range System LRS A useful COTS upgrade for the RC system for this particular case is an Long Range System LRS Typically they consist of a small box transmitter mounted on the back of the existing transmitter coupled with a matching receiver like any other that is attached to the on board equipment The advantage of the LRS is it just connects right to an existing transmitter allowing the RPV model to travel long distances The major problem of this system is it might cause electrical interference in the video and disturb it This happens due to spurious emissions which refers to any signal that comes out of a transmitter other than the wanted signal Harmonics is one type of spurious emissions and they are the multiples of the operating frequency of the transmitter If one harmonic falls on the frequency being used by the video system then this sourious emission can prevent the video signal from being properly received To avoid interferences with the harmonics in addition to the good design of the amplifier the transmitter output 16 could be filtered with a low pass filter to reduce the level of the harmonics The filter will pass the desired frequency and reduce all harmonics to acceptable levels Although a lower frequency like 35 MHz would provide t
24. inputs and plug the servos and motor controller into the APM outputs Table 5 1 shows how the female to female cables should be connected the ground black wire of each connector should be on the outside closest to the edge of the board Each channel that the pilot wants the APM to control should be connected to the corresponding input on the APM board An extra pin was activated in the Scherrer s Rx to manipulate the autopilot function Channel 6 This channel will allow the pilot to change between manual and automatic flights by controlling the PWM value As for the output pins the way to plug the servos and other devices for the APM to control is shown in Fig 5 1 the ailerons are attributed to pin 1 the elevator to pin 2 throttle to pin 3 and rudder to pin 4 3 Robotics Figure 5 1 4 Channels plane setup 63 The flight controller must be facing forward the GPS connector should also face forward The board must also be right side up Fig 5 2 a with the Inertial Measurement Unit IMU shield at the top lt is important that it is attached with velcro to the airframe and mounted on a solid platform as seen in Fig 5 2 b so that it does not move around during flight be as close as possible to level when the plane is in its flying orientation and also it would have to be as close to the center of gravity as possible because that is where the vibration is the least lt is also necessary the supplied APM Power Module for the
25. long range transmitters With a resonance noise floor of 90 dBm it is easily noticeable that the OpenLRS has the best transmitter s input filter meaning that it will be producing much less noise onto a video receiver than the others being the second best the ScherrerLRS However this issue does not mean that the OpenLRS will fly longer ranges it means that the control and video systems will not interfere with one another as much 26 The output power of the Scherrer is variable from 0 5 to 2 W the EZUHF from 0 2 to 0 6 W the DragonLink from 0 25 to 0 5 W the OpenLRS has a fixed output power of 1 W The physical specifications of the systems are also important as the UAV demands less space payload and power consumption and they are compared in Table 3 2 The Scherrer RC system was selected because it has been proved to perform more than 100 km range Roberto Montiel from Section 1 2 compared with the other systems it is the second with less phase noise The sensitivity of the OpenLRS is the lowest of the lot From the type of modulations all 17 Scherrer Immersion EZUHf DragonLink OpenLRS Size mm 26x54x18 70x30x17 49x84x28 N A Weight g 20 22 22 N A Range km 100 70 50 N A Sensitivity dB 114 112 115 118 Modulation PPM FSK N A FSK LRS Price 450 350 225 160 Table 3 2 Comparison of physical specifications for the long range system systems are digital meaning they are less affected by interferences Analogue si
26. material Fig B 2 b shows the final result a Test for Thrust b Final Result for the support of the motor Figure B 2 Radio link system configurations With a new platform built 3 different propellers were tested and Table B 6 shows the thrust calculated for each one P W MA V T kg 9x6 288 24 12 1 13 10x5 303 25 12 15 11x55 372 31 12 18 Table B 6 Experimental Data for each propeller using the same OS engine The 10x5 was chosen since it provided an increase of 25 in thrust with just an increase of 5 in input power 97 98 Appendix C Sub systems Schematics Figure C 1 Video transmission schematic 99 j C ARRERA gt vi AN maf Ola FDR RADIO gt lt eee ori e Vt SDE ALRSREED Sewa Tosg Tlesiia i us Tex Ka u Bl he fbi Figure C 2 RC sub system Schematic 100
27. radio On the other hand the LRS can affect the TR if the antennas are touching each other or if the LRS is emitting 2 W and they are very close together The Yagi having the transmission directionally channelled has more influence on the telemetry trans mission However it can also be seen that if the antennas are reasonably away from each other the interference is almost null 96 In conclusion although the TR is the weakest sub system for the desired long endurance flight it can still be a useful tool Supposing an electric UAV powered by solar panels the TR allows the user to make changes to a predefined mission without having to land it It will just have to be in loiter mode in a 1 km range This reduces the risk of damaging the UAV when landing 6 4 Testing the Interaction between Video and Communications Systems The objective of this experiment is to evaluate the interference between the communications link and the video link First it is important to understand why this test is useful On one hand the onboard video system emits strong RF signals in its primary frequency and also in other frequencies there is usually noise from spurious emissions These RF emissions can greatly affect the link of surrounding equipments such as RC receiver GPS receiver stabilization systems and servos On the other hand GCS wise the same goes for the RC transmitter lts third harmonic can affect the video link quality if the noise pr
28. that enables long range flights including the primary compo nents such as a camera camera gimbal transmitter and receiver on screen display with telemetry data ground display and antennas e Design and setup of a control system that enables long range flights including the primary com ponents such as remote controller LRS transmitter and receiver and antennas e Radio Control range tests in a controlled environment such as a signal strength as a function of distance b antenna directivity e Video range testing in controlled environment such as a propagation loss b polarization loss c antenna pattern null and d signal obstruction and e antenna directivity e Implementation and validation of the purposed setup by means of analysis of quality and range in actual flight tests taking into account in both systems the importance of a distance b baking c signal obstruction d antenna directivity e Development of a platform capable of communicating at long distances that is not an end in itself but an open project that can be used for many purposes depending on the will of the project it is inserted in A final antenna configuration was reached and 2 m above the ground the video configuration as seen in Fig 8 1 a showed a maximum range of 8 km while the RC configuration as seen in Fig 8 1 b also 2 m above the ground proved to be able to perform at least 8 km After gathering conclusions regarding the
29. the amount of energy reflected by the antenna is defined by the fact that if the antenna is perfectly matched with the transmitter it will use 100 of the energy that the transmitter delivers As this adaptation becomes worse by the design of the antenna or because the frequency to be transmitted is not the resonant one the antenna will gather a lower percentage of the energy delivered by the transmitter The spectrum frequency is summarized in Table 3 6 Like it was said before UHF 300 3000 MHz is required when covering large areas with little control over the receiving installation 21 andno Symbol Frequency range Wavelength Corresponding symbol metric subdivision of wavebands ELF lt 300 Hz gt 1000 km 3 ULF 300 Hz 3 kHz 1000 100 km Hectokilometric B hkm 4 VLF 3 30 kHz 100 10 km Myriametric B Mam 5 LF 30 200 kHz 10 1 km Kilometric B km 6 WIF 300 kHz 3 MHz 1km 100 m Hectometric B hm T HF 3 30 MHz 100 10 m Decametric E dam 8 WHF 30 300 MHz 10 1 m Metric B m 9 UHF 300 MHz 3 GHz 1m 100mm Decimetric B dm 10 SHF 3 30 GHZ 100 10 mm Centimetric B cm 11 EHF 30 300 GHz 10 1 mm Millimetric B mm 12 300 GHz 3 THz 1 mm 100 um Decimillimetric B dmm 13 3 30 THz 100 10 um Centimillimetric B cmm 14 30 300 THz 10 1 um Micrometric Bum 300 3000 THz 1 0 1 um Decimicrometric B dum Note 1 band number N N band number extends from 0 3 x 10 to 3 x 10 Hz Note 2 prefix k kilo 10 M mega 10 G giga 10 T tera 10 m
30. the features and functionalities of the MinimOSD Here it is possible to access the source code if there is the need to configure some extra feature like for example for getting RSSI from the control receiver The firmware for the MinimOSD in this particular case is the MinimOSD Extra Plane Pre release _2 4_r719 hex while the configuration tool is the CT Tool for MinimOSD Extra 2 3 2 0 Pre Release r727 zip Inside the zip file there is an executable file that auto matically runs ConfigTool The first step is to enable this function in the APM so that it can communicate with the MinimOSD Extra as it was explained in Subsection 5 1 2 After the firmware update the charac ter set a mcm file comes next for the character set both sides of the MinimOSD have to be powered one side from the USB port and another from the video pins with a 3S LiPo battery For this dissertation an important feature of the OSD is the RSSI output The RC receiver the Scherrer Rx 700 has an extra output pin on channel 12 for RSSI out This pin will send a voltage of 2 2 V when the connection is at 100 and 1 1 V when it is at 0 As shown in Fig 5 4 this spot was soldered to a pin so that Ch12 becomes a 4 pin channel Two wires are then connected to the APM the RSSI and ground as it can be seen in Fig 5 4 For the APM to recognize the RSSI in it has to be configured in the Mission Planner MP The way to do this is to connect the APM to the MP next go to
31. was hard to point the antenna to where the UAV was exactly and for this reason the design of an antenna tracker using COTS products is addressed in this appendix This approach significantly improves the range over which signals can be both sent and received from the ground station A 1 Problem Statement Designing an antenna tracker for the purpose of this dissertation has two different ramifications 1 using the equipment already available and 2 designing it for long range With the available equipment there are two possible approaches 1 Using the Telemetry 3DR radio to provide the tracker the GPS coordinates to determine Azimuth heading and direct the antennas ltem Using a system that instead uses raw signal strength RSSI The first uses the 3DR radio which is a transceiver with an output power of 100 mW which was not designed for long range flights It would be possible to adjust that coupling it with a high gain and very directional antenna like a parabolic dish The main problem of using the 3DR transceiver is that the ground station would have three antennas with two of then working in the 433 MHz frequency band which is not advisable due to interference reasons The second design is retrieved from a post of Alexander Greve in RCGroups 71 that designed an antenna tracker which instead of using GPS coordinates to determine azimuth heading to direct the antennas beam uses raw signal strength RSSI This way there will be
32. when increasing height Its intensity becomes negligible at about 1 wavelength over ground and 5 to 10 over sea water The best type of surface for surface wave transmission is sea water The electrical properties of the terrain that determine the attenuation of the surface wave field intensity are very little Omnidirectional antennas are not isotropic and typically have nulls in their radiation pattern aligned with the antenna axis If the Tx antenna is somehow pointing to the Rx antenna the effective gain of the Tx is much lower and this effect will add extra loss to the video link The most common situation of antenna radiation pattern null is when the UAV is flying over the GCS 22 36 Chapter 5 Setup of the Unmanned Air System 5 1 Setup of the RPV Airframe Turning a RC plane into an UAV implies putting a flight controller between the RC receiver and the aircrafts servos so that it sends telemetry data through the OSD and the pilot can orient himself through the monitor display and to enable the autopilot function so that the flight controller can take over control when the pilot desires so 5 1 1 APM 2 5 Between the Rx and the Servos Channel TSLRS APM 1 Throttle Ailerons 2 Ailerons Elevator 3 Elevator Throttle 4 Rudder Rudder Autopilot 6 8 TSLRS Rx700 APM 2 5 Table 5 1 Connections between the APM and the Rx700 The way the APM 2 6 is connected is to plug female to female cables from the RC receiver into the APM
33. 37334 Table 6 10 Obtained GPS latitude with video transmitter off and on Time s Real Longitude GPS Longitude off GPS Longitude on 10 9 136955 9 136892 9 136943 20 9 136955 9 136955 9 136937 30 9 136955 9 136898 9 136937 40 9 136955 9 136897 9 136925 50 9 136955 9 136926 9 136917 60 9 136955 9 136917 9 136919 Table 6 11 Obtained GPS longitude with video transmitter off and on Table 6 12 shows that the reading of the GPS has an error associated with the receiving data How ever that error does not seem to be aggravated with presence of the video transmitter Concluding with this test there seems to be no interference of the video Tx on the GPS receiver Video Tx with RC Rx Regarding the RC receiver it was necessary to check if the onboard video transmitter was interfering with the RC Rx For this the whole system was used so that the MinimOSD would state the value of the RSSI on the ground station screen as explained in Subsection 5 1 3 61 Time s Video Off m Video On m 10 5 7 4 4 20 0 0 2 2 30 6 2 4 4 40 6 9 3 8 50 5 2 5 8 60 3 3 3 9 Table 6 12 Read distance from real UAV position with transmitter off and on ee YA Lab ee 8 Figure 6 16 Outlook of the test for the Interferences of the Communications on the Video System First Table 6 13 shows the testing of the the servos in the same way as in Section 6 1 for movement continuity and the ability the reach
34. 7 Flight Testing When changing from a controlled to a free environment where the UAV is going to fly the most important thing is to minimize possible errors The first set of variables is weather conditions In here there are two that can kill the mission strong wind and precipitation Strong wind can change a stable flight into a total disaster rain on the other hand not to talk about electricity and water can greatly affect the video quality by the sudden and multiple changes in the refraction factor causing multipath interference as mentioned in Section 4 2 Updated weather conditions were retrieved from websites 68 and 69 where it is possible to obtain wind speed gusts and direction temperature and humidity Before each flight it is important to check as in Fig 7 1 if the UAV is giving the correct GPS coordinates and if the distance home is nearby because in case of permanent link loss the UAV will head for the predefined Home When the UAS is turned on the GPS will lock this location as Home lt is also important to check the servos response and battery charge oo TAT OOOO e Figure 7 1 GPS lock is an important pre flight check 7 1 Short Range Flight Test Before a long range flight the link quality was studied first with short range flight tests One of those flights is analysed here The chosen date for this flight test corresponded to favourable weather condi tions as specified in Table 7 1 Th
35. 9 issues When analysing video quality it is important to have in mind a few issues that often occur with video systems and they are e Propagation loss e Polarization loss e Antenna radiation pattern null e Signal obstruction These issues are mentioned in Section 4 2 where it is explained how it is possible to replicate them and this is what was tested with the various antennas configurations Table 6 2 indicates how in theory these problems can be solved Video Issues Proposed Solutions Circular polarization naturally rejects multipath as the polarization change from left hand to right hand with signal bounce Diversity at the receiver end Two antennas at the transmitting end with a separation of at least one wavelength from each other Higher gain antenna Propagation Loss More transmitting power More receiver sensitivity Circular polarization will give no polarization losses Diversity at the receiver end with one antenna vertical and the other horizontal Diversity at the receiver end Two antennas at the transmitting end Radiation Pattern Null with two video transmitters tilted 45 deg relative to each other Diversity at the receiver end Two antennas at the transmitting end Signal Obstruction with two transmitters working in different frequencies placed in both wing tips this way the probability of obstruction is much smaller Multipath Polarization Loss Table 6 2 Proposed Solutions
36. For radio control there are three forms of radio frequency RF communication systems 1 simplex radio technology that allows only one way communication from a transmitter to a receiver 2 half duplex operation mode in which each end can transmit and receive not simultaneously 3 full duplex each end can transmit and receive simultaneously In order to control the UAV from the ground station a simplex communication system is required A basic simplex communication system is composed by the building blocks from Fig 3 2 21 Tranarnitter Modulator Amplitiar Low Frequency Information Signal Intelligence High Frequency Carrier Receiver Figure 3 2 Basic building blocks of a RF system 21 The RF modulation is part of the transmitter will combine data into a carrier wave at a standardized frequency as required by the receiving equipment The demodulator on the other hand is part of the receiver and will perform analogue demodulation extracting the original information bearing signal from the modulated carrier wave 21 The signal output from a demodulator may represent sound an analogue audio signal images an analogue video signal or binary data a digital signal There are three major types of signal modulation 1 Pulse position modulation PPM is one form of signal modulation in which message bits are encoded by transmitting a single pulse in one possible time shift repeated ev
37. I0Ut m nn nn 46 6 3 Points along the coast where the Radio control experiment took place 46 6 4 Changing the output power and antennas of the transmission 48 6 5 Video link system configurations 2 222 2 2 mm nn nn 49 6 6 Points along the coast where the experiment took place 51 6 7 Effect of propagation loss in video quality 52 6 8 Video Quality affected by propagation loss 2222 2 mm nn nn 53 6 9 Tests Of telemetry radio 22 22 2 Ho nn n nn 55 6 10 Test of the telemetry radio link system configurations 0 4 56 6 11 Ground station interferences and outlook 58 6 12 Ground station interferences and outlook o o 59 6 13 At a distance of 8 km with only the video system circularly polarised configuration 59 6 14 Video System coupled with the onboard RC equipment 59 6 15 Comparison between the overall video quality in standalone and installed configurations 60 6 16 Outlook of the test for the Interferences of the Communications on the Video System 62 6 17 Camera gimbal setup nn nn 63 7 1 GPS lock is an important pre flight check om En 67 7 2 Line of travel for the short range Flight 0 nn 68 7 3 RSSI versus distance home nn nn 68 7 4 RSSI versus the Roll of a certain m
38. Signal Strength Indicator RSSI It is not required that a vendor uses all 225 values so each vendor will have a specific maximum RSSI value making the RSSI an arbitrary integer value that depends solely on the vendor Nothing regulates the unit of measure of the RSSI it can be dBm or mW Regarding the strength of RF signals on the Scherrer device RSSI sensors on board of the UAV are able to measure that across a range of frequencies The signals although noisy and ambiguous due to structural noise allow estimates to be made of emitter locations The RSSI output is an analogue voltage that reveals how strong the signal arrives to the receiver lt is possible to predict the range of a transmission with the antennas in line of sight without any obstacles with the Friis transmission equation 40 This equation gives the power received by one antenna under idealized conditions given another antenna some distance away transmitting a known amount of power The Friis equation states given two antennas the ratio of power available at the input of the receiving antenna P to output power to the transmitting antenna P F Te Leo 1 Pi on Ir where G and G are the antenna gains with respect to the isotropic radiator of the transmitting and receiving antennas respectively A is the wavelength and R the distance between the antennas The inverse of the factor in parentheses is called free space path loss The equation also has to consider a fad
39. TECNICO LISBOA Design of a Remote Person View System for a Long Range UAV Pedro de Oliveira Martins Gersao Miller Thesis to obtain the Master of Science Degree in Aerospace Engineering Supervisor Prof Andr Calado Marta Examination Committee Chairperson Prof Filipe Szolnoky Ramos Pinto Cunha Supervisor Prof Andr Calado Marta Member of the Committee Prof Agostinho Rui Alves da Fonseca June 2015 Be the change you wish to see in the world Mahatma Gandhi Acknowledgments want to dedicate this section to thank my supervisor Professor Andr Marta for his dedication through out the elaboration of this dissertation would also like thank Professor Agostinho Fonseca for his helpful advice and Professor Carlos Fernandes for kindly providing his useful information upon estimat ing ranges would also like to thank Bernardo Reis for so eloquently flying the UAV and Alexandre Cruz for all his technical support This project is the culmination of the last five years of completing my degree which would not be possible without the friends made in this time So a very special thanks to my classmates who accom panied me throughout the several challenges that arose and without whom this time would not have bee as much fun and fruitful as it was want to express my gratitude to my family for their unconditional and essential support encourage ment and help during all my studies and also during the elaboration o
40. V autopilot system comprises of a GPS receiver an IMU and an onboard processor state estimator and flight controller as ilustrated in Fig 3 4 28 GPS Receiver BFS i Throttle State State l Aileron j e Controller _ Observer ud Estimator Elevator Sensor Measurenont Rudder Figure 3 4 Functional structure of the UAV autopilot 30 All inertial measurements from sensors are sent to the onboard processor for further filtering and control processing The strength of the autopilot software directly affects the robustness of the whole autopilot system 29 There are three basic controllers for the UAV flight control altitude controller velocity and heading controller Altitude controller is to drive the UAV to fly at a desired altitude including the landing and take off stages The heading and velocity controller is to guide the UAV to fly through the desired waypoints To achieve the above control requirements different control strategies can be used including PID adap tive neural network fuzzy logic and fractional order control Given the reference waypoint coordinates and the current UAV state estimates the controller parameters of different layers can be tuned off line first and re tuned during the flight Most commercial autopilots use traditional PID controllers because they are easy to implement in the small UAV platforms However PID controllers have limitations in optimality and robustness 28 For the
41. acteristics 46 With that said the Kx 181 CCD Sony camera was selected because as it can be seen in Table 4 1 it has the recommendable imaging device CCD 520 TVL and it is a fairly priced camera The voltage range is within the 2S 3S batteries and comes with the already stated compromised 3 6 mm focal length lens 4 1 2 On Screen Display An On screen display OSD device allows the telemetry module of the flight controller autopilot to overlay information onto the video stream which can facilitate the its navigation This information can include the UAV altitude heading direction to home distance form home velocity or power etc There are many options when considering an OSD module Most of the OSDs are designed to connect into its flight controller and get the information from there which is useful due to the fact that it is only needed a single add on board in order to have OSD capabilities Some flight controllers come bundled with an OSD built in The most important thing to consider when considering an OSD is its compatibility with the chosen flight controller All in all what to look for in an OSD is e Weight e Price e Compatibility 29 e Features In this segment three OSD devices are analysed the APM MinimOSD 47 the EZOSD 48 and the RangeVideoOSD 33 The MinimOSD is a small circuit board designed and programmed by 3DRobotics that gets telemetry data from the APM flight controller and overlays it on t
42. ain antenna in this case 13 dBi this does not mean the transmission will gain something more or it is better This just means the radiation pattern of this antenna instead of a spherical shape will vertically look like an apple and the higher the gain the bigger the difference Another important aspect of this antenna and antennas generally is its polarization In this case it is linearly polarized Theoretically this will be a problem when the UAV is performing a manoeuvre like banking However the TSLRS receiver is already compensating with its diversity system Since diversity is the feature that allows the receiver to choose out of its antennas the one with better reception a receiving antenna on the wing horizontal and another on the rudder vertical will solve this issue The A430510 from Diamond Antennas 37 was chosen because it provides a bandwidth of 430 440 MHz with 13 dBi of gain and an aperture of 30 Fig 3 7 a Also it is easily assembled and portable Figure 3 7 a shows the directivity chart for the A430510 although it provides a narrow beam of 30 this will allow the UAV to fly long distances This type of antenna is widely used for UHF bands due to its moderate gain which depends on the number of elements linear polarization unidirectional beam pattern with high front to back ratio It is also lightweight and simple to build It is priced at 79 34 22 PART E Eu ly E T San a
43. ames The EPP FPV for being the cheapest airframe and lightest weighting only 1 kg with the 2013 being the second most light with 1 8 kg is tempting but it lacks space for storing all the necessary electronics which means that they would have to be placed outside the airframe translating in aerodynamic drag The Skywalker from 2013 is the one with the most reviews and recommendations It has many videos available verifying its reliability and is the second most light For being around for quite a while its price is very reasonable The Skywalker from 2014 was found in a local shop which would mean less time spent ordering and ease the buying On the other hand the 2013 Skywalker has been around for some time and for that is much more less expensive and there are lots of flight test video of the internet showing that it is a capable and reliable airframe 91 The Skywarrior lacks in detailed description also there are no flight test video available and it is priced at 165 On the other hand the flying wing X 8 seems to be a good approach due to its interior volume for placing all the electronics Also it is made of EPP too which makes it as hard to brake as all the others It also received good reviews by the community The 2013 Skywalker is the airframe with better potential and will be the one used Although they share similar qualities but it is best to buy an airframe that has shown good results from previous users and there
44. an the standard monopole antenna 25 26 Chapter 4 Design of Video System The aim of this chapter is to describe the design of the video system used for this dissertation in which Commercial Off The Shelf COTS products are used This includes the primary components such as the camera video transmitter and receiver On Screen Display OSD also ground display and high gain antennas 4 1 Remote Person View Setup Remote Person View RPV is the method used for controlling a radio controlled vehicle from the cabin s point of view It involves mounting a small video camera and a video transmitter to an RC aircraft and flying by means of a live video down link commonly displayed on a portable monitor As a result RPV aircraft can be flown well beyond visual range limited only by the range of the remote control video equipment and batteries used A typical RPV setup makes use the following equipment as depicted in Fig 4 1 Camera On Screen Display OSD Video Transmitter Tx Video Receiver Rx Tx Antenna Rx Antenna Video Display Video Recorder The following Subsections detail the characteristics and the selection of each component 27 Camera Flight Controller DVR Display Figure 4 1 Scheme of the video system Tx Antenna Rx Antenna 4 1 1 Camera Most RPV cameras available today are primarily from the video surveillance and security industry and work very well for
45. anoeuvre 2 2 69 7 5 Overall flight data for a short range flight om mn nn 70 7 6 Banking of 39 with no image distortion 2222 2 Cm mm nn 70 7 7 Distortion due to transmission through the MinimOSD 70 7 8 UAV flown in the direction of the GCS doing 180 with the Heliaxial orientation 71 7 9 Camera gimbal operation modes 22 22 Ca on m nn 71 7 10 Flight path of the 2 2 km flight test 2 20 0 0 002 4 72 7 11 Overall flight data for a short range flight o 73 7 12 First DinPoint 1 remarks e 55 8 82 4 3 ar Sk Rn 2 a A eee 74 7 13 UAV gaining altitude and with the Helical pointed directly towards it 2 74 7 14 Remarks from pinpoints 3 to 9 1 eee 75 8 1 Final configuration for long range flights 0 002 eee ee 77 A 1 Tracker board schematics 71 2 ee 88 A 2 Antenna tracker layout 71 2 2 Coon nn 89 A 3 Alexander Greve s own prototype 71 89 XVIII B 1 9x6 Propeller characteristics 56 2 0 ee 94 B 2 Radio link system configurations 2 o 97 C 1 Video transmission schematic 2 aooaa a a a a e e a 99 C 2 RC sub system Schematic a 100 XIX XX List of Acronyms FHSS GPS LiPo LOS LRS OSD PPM RC RPV RSSI Rx Tx UHF UAV VHF Frequency Hop
46. ary domain This has allowed for expanding the use of unmanned aerial vehicles to many civilian applications In recent years the term UAV has been replaced with the term UA which stands for unmanned aircraft To emphasize that a UA is a part of a complete system including ground operator stations launching mechanisms and so forth the term unmanned aerial system UAS has been introduced and its use is becoming commonplace 18 One common feature of UASs is the use of a video system This system allows the UAV to be piloted beyond the line of sight of the pilot from a first person perspective via an on board camera fed wireless to a monitor In order to describe the components that constitute the desired UAS for this dissertation the platform was divided into two sub systems as seen in Fig 2 1 the airborne and ground station setup and the means of communication between the two In the chapters that follow the UAS was divided between video and control systems instead of the airborn and ground station systems The following subsections aim to give an overall view of these sub systems 2 1 1 Airborne The airborne equipment refers to the systems that will be flying The type and performance of the aircraft is determined by the needs of the operational mission For horizontal take off and landing HTOL aircraft the flight variables are direction horizontal speed altitude and rate of climb The direction of flight heading will be controlle
47. c center is estimated to be at 93 25 of the root chord the neutral point at 60 and the center of gravity at 48 This is the reason why the batteries the heaviest elements of the whole lot will placed as far back as possible which coincides with the 48 of the wing root chord The batteries will be placed below the canopy so the overall centre of gravity stays approximately at 50 of the wing root chord B 2 Electric Motor and Propeller Testbed Selection B 2 1 Propeller The Skywalker has the support for the motor on its back and so the propeller size is limited by the dis tance between the engine support and the airframe tail The airframe only allows a maximum diameter of 0 22 m for the propeller Because of this the chosen propeller was a 9x6 APC where the 9 stands for 9 inches diameter 0 22 m and the 6 for the pitch size as seen in Fig B 1 Length Inch X E oe Piteh Inch Y E Figure B 1 9x6 Propeller characteristics 56 B 2 2 Electric Motor In order to find a combination of electric motor and propeller that matches this UAV empirical data is used as basis supplemented by propeller data 73 The parameters that will define if the motor is suitable for the aircraft are thrust T shaft horsepower P and engine and propeller efficiencies The first assumption is that the climb stage is the one that requires more power and more thrust Assuming also that the climb will be at a con
48. cal position and so with vertical polarisation the onboard monopole antenna is changing polarisation from vertical to horizontal thus affecting the link quality see Table 6 3 On the other side of the spectrum the helical with skew planar antenna configuration for having both circular polarisation is the less affected configuration by the inclination of the UAV however it can be seen that with the increase in distance the effect starts showing some signs of weakness see Table 53 6 3 Pattern Null Distance km V v Vs H v H s 0 6 8 9 8 9 2 1 3 7 7 3 1 1 9 9 4 2 1 4 9 6 1 7 7 3 9 e Table 6 4 Antenna pattern null with different configurations and distances With respect to the antenna pattern null it is seen that both configurations with vertical polarisation in the GCS are greatly affected by the pattern null showing that the gap on top of the radiation shape is large and easy to find Thus with this configuration it is not advisable to fly the UAV over the GCS As for the Helical configurations it is seen that this gap is difficult to find although it increases with distance see Table 6 4 Obstruction Distance km V v Vs H v H s 0 6 7 7 10 7 2 1 1 7 7 3 1 1 3 5 4 2 1 2 4 6 1 1 7 1 9 E 3 E 2 Table 6 5 Obstruction with different configurations and distances The case of obstruction is the one that affects the link in most ways if using a vertical polarisation in the GCS the
49. ch channel is encoded as a scalar value based on the position of the interface which is usually composed of two joysticks each with two degrees of freedom The functionalities to look for in a remote control transmitter are e Price e Number of channels e Modes e Compatibility with Long range systems Each channel allows one individual function on the aircraft For example for turning left or right for pitching forward or backwards for throttle and for rolling left or right Four channels is the minimum for the required UAV pitch roll throttle and yaw With a remote with more than four channels there is the choice of using switches or potentiometers to change settings on the UAV during flight When using a flight controller the minimum number of channels increases to five the extra channels is to switch between different flying modes 15 Regarding compatibility the transmitter has to enable PPM signal modulation In the features of the RC remote there has to be the capability of student function see list of acronyms and to be compatible with PC simulators Its down side is the price being the most expensive component in the whole system with a cost of 1000 The Graupner mc 24 was chosen because of it popularity amongst pilots and for its 12 controllable channels switches and potentiometers with internal or external telemetry Also it gives the pilot the freedom to programme everything like he wants to have it This bec
50. cts of Video Transmissions 0 0000 Setup of the Unmanned Air System 5 1 SOU OF ING RV AIG side dc hh Gm SR eae 5 1 1 APM 2 5 Between the Rx andthe Servos 2 00000 5 1 2 Flight Controller Configuration nn Sto MNMOSD Setups 2 22 3 8 one BOP Se SEES RAD ewe ee E 5 1 4 Video Transmitter Setup ea 2 2 oe ra al a 52 S6t p OF the Ground Stalo a amp a gi oe ddr en de o a Se CONTO Stato Selup yd msgs a ae es dd eR A gerne dez RPV Staion SeU aaa sabia Ed ei Sub Systems Testing in Controlled Environment 6 1 Testing of the Radio Control Link Systems 0 2 0000 a Gilet MESTIDESION s ax a Oia ara oe eee ee oS RRO Dee e 8 12 ICSDMCSUINGS ss Ria Tae wide dorms E A A At ae ede 6 2 Testing of the Video Link System es 6 21 Tesi Desig dci a aes Goad a BE a ea 622 TES ACSUNG sacar dp aa ar Bie ke be oe e Bp Ee 6 3 Testing of the Telemetry Radio nn 6 3 1 Testing of the Telemetry Radiorange 2 02 00 ee 6 3 2 Testing the Interference between the Telemetry Radio andthe TSLRS 6 4 Testing the Interaction between Video and Communications Systems 6 4 1 Ground Station Interferences 2 2 22mm 0 000 ee 6 4 2 Onboard Interferences paus cia aa Aa 6 4 3 Ran a a UN Iesing s criada ao Ban ei ann 6 5 Testing of the Energy Consumption 0 m nn xii 27 27 28 29
51. d by a combination of the servos responsible for the rudder and ailerons the horizontal speed will be controlled by voltage regulator of the propulsive thrust and elevator deflection Finally the rate of climb to a given altitude is achieved by the application of a combination of elevator Antenna Video Display Rx recorder Monitor LRS Tx Rx Antenna pen mm Cotroller Figure 2 1 UAS Functional structure deflection and propulsive thrust All the servos are connected to the receptor that receives orders from the transmitter or autopilot depending on the type of flight operation As for the navigation system described below the degree of autonomy in a UAS can vary greatly ranging from teleoperation to fully autonomous operation Teleoperation is a mode of operation where the UAV is commanded by a human operator using a remote controller from the ground In this mode of operation the degree of autonomy is minimal because continuous input from an operator is required Fully autonomous UAVs are characterized by the ability to maintain flight and to carry out complete missions from take off to landing without any human pilot intervention Regarding ways of navigation the operator can be either piloting the UAV from sight which gives the system a reduce area of operation or it can be piloted through a video system monitor which gives the pilot an on board view This type of piloting is usually called remote person view RPV and greatly
52. d positions Margins in each checkpoint for the six possible antenna configurations Since both configurations only started showing signs of weakness at km 7 the table begins at the previous checkpoint and ends at km 8 due to the fact that the coast started retrieving thus imposing obstacles to the transmission From Table 6 1 it is possible to see that regarding the monopole antenna e The connection ends between 4 and 7 km It is noteworthy that between these checkpoints the connection breaks no matter what the output power is It suggests that output power on the monopole does not make any difference e t has a range of at least 4 km and regarding the Yagi antenna 47 e The signal gradually loses its strength from the 7 km checkpoint Using different output powers it is possible to see the gradual decrease from the 7 km to the 8 km mark e The maximum registered range is at 8 km However with 1 W the servo was still moving going for its extremities but at an inconstant pace While with 2 W the servo started moving continuously towards its margins This means that the maximum range is at least 8 km e While the monopole handles 4 km the Yagi antenna doubles the range of the connection 100 x KR Whip 0 5W 100 i N E Whip 1W 90 PRO u 80 N an E Yagi LW 70 N k li ho a de Yagi IW x 60 SER oo y a 50 e mn N 550 nM E 40 gt Hao 4 as aa 30 1 5 20 20 10
53. dard whip antenna Information retrieved from private e mail conversation with Juan Sircana Accessed 2015 02 24 67 Telecommunication Standartization Sector of ITU Subjective video quality assessment methods for multimedia Recommendation ITU T P910 2009 68 Windguru http http www windguru cz Accessed 2015 04 16 69 Accuweather http www accuweather com pt pt portugal weather Accessed 2015 04 16 70 The rssi is very inconstant while cruising or manoeuvreing the rssi can vary from 93 to 70 Informa tion retrieved from private e mail conversation with Aram Robledo 3DR Tech Support Engineer Accessed 2015 04 24 84 71 Alexander Greves Do lt Yourself Antenna Tracker http www rcgroups com fo rums showthread php t 1337608 Accessed 2015 05 10 72 B Etkin Dynamics of Flight Stability and Control John Wiley amp Sons Wiltshire United Kingdom 1995 73 APC Propellers 9x6 performance datasheet December 2014 74 T C Corke Design of Aircraft Pearson Education 2003 ISBN 13 978 0130892348 75 Maximum lift coefficient of the skywalker airframe http www rcgroups com forums showthread php t 1223595 amp page 525 Accessed 2014 01 30 85 86 Appendix A Design of an Antenna Tracker Antenna Trackers are systems that track the UAV s location and use this information to correctly align a direction antenna From ground and flight testing it was found that in long distances it
54. e which is being developed in a collaborative project by the departments IDMEC from Instituto Supe rior Tecnico INEGI Faculdade de Engenharia da Universidade do Porto and AeroG Universidade da Beira Interior under the sponsorship of LAETA Laboratorio Associado de Energia Transportes e Aeronautica 17 The main goal of the project is to develop a low cost smart footprint electric UAV capable of being deployed from short airfields easy to build and maintain and high flexible to perform different civilian surveillance missions The main specifications of the RPV system include e Long Endurance accomplished by using green power technologies such as an electric propulsion system with solar power This includes the use of highly efficiency solar cells high capacity density batteries efficient compact motors and appropriate long endurance aerodynamic design e Autonomous Flight accomplished by equipping the UAV with autopilot navigation systems such as inertial guidance systems and GPS e Obstacle Avoidance accomplished by implementing an obstacle avoidance technique that in cludes detection estimation and avoidance planning of the obstacle e High Strength Low weight Structure accomplished by using composite materials with fuse lage wing critical areas designed for good impact resistance on landing using easy to manufacture techniques e Multiple Mission accomplished by designing a sufficiently large payload
55. e RC system 27 oo nn nn 18 Functional structure of the UAV autopilot 30 o 19 Telemetry Radio from 3DR Robotics ee e o 21 Types of propagation directions of an antenna 36 22 Long range RG System 3427 uc a 88 2 RES nahe id a a E 23 Scheme of the video system 2 manene Ea E 28 MinimOSD from 3DRobotics 47 22 2 22 22mm 31 Video system developed by Partom nn 32 Skew planar wheel SPW12 1200 1360 MHz Antenna 53 33 Helical 12 910 1680 MHz Antenna 54 33 Recording and displaying devices nn 34 Types of Wave Propagation 2 2222 mn m nn nn 36 4 Channels plane setup 63 En 38 Concerns about the mounting of the APM a 38 MinimOSD between the APM and Video Transmitter Schematics 39 APM reads RSSI from Ch12 to channel A o 40 Configuring the MinimOSD to correctly read the RSSI values 41 Graupner mc 24 coupling with Scherrer TX 2 2 222 2 mE nn 42 Control station connection schematic 2 2 22 nun nn 42 RPV station connection schematic 2 2 2 mn m 0 e 43 5 9 Final result for the UAS setup on the day of the first flight 43 6 1 Radio link system configurations 22 22 2 om n nn 46 6 2 Mission Planner reading RSS
56. e Srna STE gp A 27 km Flickering Flickering gg Mov E 6 km Mov continuity Continuity 4km ee AR Borders m i Tkm Contrast Contrast a ey 2km cc Colours 0 2 4 6 Rate for Quali c Heliaxial GCS Vertical UAS d Heliaxial GCS Skew Planar UAS Figure 6 7 Effect of propagation loss in video quality Contrast colours and image borders seem to be equally affected by the distance and so video can be classified by a generalized parameter an overall image quality The points attributed to the these parameters where used to build an average score A representation of that evaluation in shown in Fig 6 8 where the overall video quality is rated as a function of distance Regarding Figs 6 7 and 6 8 there are several things that are noteworthy e The best configurations have the Helical on the GCS since good video quality goes much further in range This may be due to the fact that the receiver for having a higher gain antenna is concentrating its focus into a more specific area and can interpret the signal much easier More specifically the system works best if the helical is coupled with the Skew Planar because they have the same polarisation e The configuration with the vertical antenna on the GCS and the skew planar onboard seems to be the worst For having different polarisations it is the one where the connection is the worst and totally losing it at the 6 km mark e T
57. e UAV comparing the voltages between the two Rx and the third unit will be the receiving module Locating the RSSI pins in the receiver is done by checking voltages on each pin turn on and off the radio Tx and see which pin changes voltage The RSSI buffer reduces the impedance of the RSSI and disconnect it from the circuit when it changes state using the Operational Amplifier LM358 The signal comparator does the actual selection of the signals Its inputs are the two RSSI voltages and it outputs a 5 V or O V signal This tells the channel selector which unit to select Once selected the output is then buffered through an adjustable Schmitt trigger circuit by adding a single potentiometer to 88 the LM393 to keep it from switching unnecessarily fast between the two units Fig A 2 shows the printed circuit board layout of the antenna tracker To t2 Dattery Notes 1 AIRED wires are 12V 2 Brown wire is 5V 3 147805 is shown from the front side 4 The 30K resistor is 2 15K resistors in senes back to back i 5 The 1 MegaOhm pot adjusts the duty cycle 6 The 100K pots adjust the centering calibration 7 The 4 7uF capacitor may be changed for a 2 2uF to lessen oscillation with higher power servos 8 Circuit voltage range is from 9V to 15V 9 itis recommended that the circuit be taid out on the board as shown here 10 Al capacitors should be mounted so that the side with the gray sinpe s connected to ground battery
58. e control and video subsystems for the unmanned air system UAS of a long endurance electric UAV The tests will be done in a way that both video and remote control are approved in a controlled environment and then perform a series of flight tests where both systems are evaluated in its range and quality 1 5 Structure of the Document This work is divided in four main stages the design of the control and video sub systems Chapters 3 and 4 setup of the whole Unmanned Air System Chapter 5 testing in controlled environment Chapter 6 flight testing and conclusions Chapters 7 and 8 In Chapters 2 3 and 4 it is made a description of typical RPV systems including both control and video sub systems followed by a benchmark of commercial solutions Then comes a detailed description of the design of both the control and video sub systems and construction of the same Chapter 5 After characterizing the whole unmanned air system both control and video sub systems are tested in a controlled environment Chapter 6 followed by flight testing Chapter 7 and the respective results are presented Chapter 2 Description of the RPV System 2 1 Description of UAV Systems An unmanned aerial vehicle is an airborne vehicle without a human crew on board Historically the term and the primary use of UAVs have been in the military area Continuous development and technology transfer has lowered the cost of accessing the technology outside the milit
59. e curvature of the earth s surface by reflecting off of the atmospheric layers or refracting through atmospheric layer boundaries This allows the conclusion that the lower the frequency the longer the communication distance As frequencies get higher the tendency is for the signal to pass through the layer boundaries rather than reflecting on them The result is shorter range with power not being a factor However higher frequencies in the range of GHz signals have the ability to send signals with much better quality The aim is to get a system that has a good compromise between signal fidelity and signal quality e Effective Radiated Power ERP of the Transmitter Effective Radiated Power is the standard ized theoretical measurement of radio frequency energy and is determined by subtracting system losses and adding system gains It takes into consideration transmitter power output transmis sion line attenuation electrical resistance and RF radiation RF connector insertion losses and antenna gain e Sensitivity of the Receiver The sensitivity is a measure of the quality of a receiver and is related to the signal noise ratio SNR Sensitivity is the mnimum magnitude of input signal required to produce a specified output signal 23 3 1 1 Remote Control Transmitter The transmitter Tx is usually built into the hand held controller which encodes movement from the fingers of the pilot into several channels of flight control data Ea
60. e flight test was conducted at Pista de Aeromodelismo de Corroios This provided a safe place where the pilot could test all the actuators of the UAV and test climb cruise banking loiter descent and 6 Condition Value Wind velocity km h 15 Gust km h 20 Direction West Temperature C 14 18 Humidity 55 Table 7 1 Weather conditions during short range flight test finally landing The goal of this test was to perform a simple flight where RPV system was installed so that the pilot could perform the whole flight by looking at the screen and data could be retrieved 7 1 1 RC Link Quality The pilot performed a manual flight around the track and the values for RSSI were retrieved to see the variations in RSSI within a maximum range of 340 m Figure 7 2 Line of travel for the short range Flight The flight path is shown in Fig 7 2 Figures 7 3 and 7 4 show the variation of the RSSI as the distance home and roll change over time Before evaluating the level of RSSI it is important to say that the Yagi antenna was never moved during the whole flight in order to evaluate the directivity of the antenna it was placed always facing NorthEast with an output power of 500 mW 120 5 T 400 PPR 96 150 Dist Home m RSSI 3 oa oo o So o So YS _ gt E r Aa gt rau 4 tw ho w B e Dist Home m 1 2 3 0 00 1 12 2 24 3 36 4 48 6 00 7 12 8 24
61. e margin which is a design allowance that provides for sufficient system sensitivity to accommodate expected fading for the purpose of ensuring that the required quality of service is maintained It was assumed that a 20 dB fade margin would suffice Table 3 7 provides the required data for calculating the range of the transmission To calculate the range the Watt unit was converted to dBm using Eq 3 2 according to 22 24 yldBm 10log 1000x W 3 2 Monopole Yagi Frequency MHz 433 433 Output Power dBm 26 99 26 99 Sensitivity dBm 113 113 Receiving Gain dBi 2 2 Transmitting Gain dBi 3 13 Fade Margin dB 20 20 Communications Range km 56 160 Table 3 7 RC link range with both monopole and yagi antennas Knowing the frequency f it is possible to calculate the wavelength by Eq 3 3 where c is the speed of light which gives 0 69 m for both antennas with a 433 MHz Amer 3 3 The range is given by Eq 3 1 or it can be calculated adding the fade margin of 20 dB by Range m O P G G 20 log o A P Fm 20 3 4 where Fm stands for fade margin Equation 3 4 retrieved from 41 is valid for propagation in free space without obstacles and it gives the value of the received power on the antenna Although these ranges are very optimistic because they do not consider interferences and obstacles it is possible to conclude that theoretically the Yagi antenna will provide almost three times more range th
62. enter of gravity CG location range is usually between 28 and 33 ahead of the aircraft neutral point this is called the static margin which should be between 5 and 15 ahead of the aircraft neutral point The simplest way for calculating the neutral point is by using the areas of the two horizontal lifting surfaces as in Eq B 2 Astab D Lx Mi B 2 Awing ES Astab l where D is the distance between the neutral point and the main wing aerodynamic center and L the distance between the two aerodynamic centers Asta the area of the stabiliser Awing the wing area For aircrafts with different aspect ratios in the two lifting surfaces a more accurate result can be obtained by the use of the tail volume ratio as in Eq B 3 72 92 4 A Stabe L D V AR0 25 B 3 AV Auer oes MAG wig l The operating handbook of every airplane specifies the range over which the CG is allowed to move Inside this range the airplane is considered to be inherently stable which is to say that it will self correct longitudinal pitch disturbances without pilot input However in the Skywalker manual there is no indication of this margin and so an estimate for the position of the center of gravity will have to be made H Aircraft Center of Gravity Calculation Wing Root Chord m 0 23 Wing Tip Chord m 0 21 Wing Sweep Distance m 0 02 m Wing Half Span m 0 9 Stabiliser Root Chord m 0 17 Stabiliser Ti
63. er mc 24 that is not mentioned the remote control has to receive a PPM signal from the mono jack end tip and ground from the base as seen in Fig 5 6 a So the wire is cut which in fact is three wires PPM Ground and Power and the mono jack is welded as seen in Fig 5 6 b a From stereo to mono adaptation for the mc 24 b Mono jack transformation Figure 5 6 Graupner mc 24 coupling with Scherrer Tx The connections were made and the binding procedure was done the receiver confirming it with a fast blinking mode and the transmitter with a permanent red light on The ground control station is then composed by the radio control transmitter the long range transmitter TSLRS Tx700 and a Suitable antenna as illustrated in Fig 5 7 Figure 5 7 Control station connection schematic 5 2 2 RPV Station Setup The RPV ground station is composed by a video receiver and suitable antenna a digital video recorder and a LCD monitor as illustrated in Fig 5 8 These components have an operating voltage of 7 to 18 V LCD screen 5 to 30 V DVR and 7 to 12 V video receiver and so they will all be powered by a 3S 42 LiPo with 4200 mAh capacity Figure 5 8 shows a scheme of how the ground station is powered Since the video receiver will be attached to the helical antenna it must be placed far away from other devices and the control antenna not to be affected by external interferences SMA output Connector Figure 5 8
64. erence the video system is affected by the overlaying panels The use of the MinimOSD adds noise to the video Also the recommendable channel to be transmitting on is between 7 and 9 including It is also noteworthy the fact that the entire experiment was performed with the RC system with 2 W of output power so that the hypothetical interference was as strong as possible 60 6 4 2 Onboard Interferences The objective of this test is to evaluate the interference of the onboard video Tx on the onboard receiving equipments GPS ardupilot APM and TSLRS Rx The equipment used is e Video Tx and antenna e APM Ardupilot e GPS e Radio Control Rx e Servo The place in Fig 6 6 is again used for the onboard interferences test From Section 6 1 the maximum distance that the monopole antenna signal can travel with 0 5 W is between 4 and 6 km Video Tx with GPS Regarding the interference of the video Tx on the GPS receiver a simple test was performed The video Tx antenna was right next to the GPS and for 1 minute the GPS coordinates from Mission Planner were retrieved as it is shown in Tables 6 10 and 6 11 The values were written with both the video Tx on and off Time s Real Latitude GPS Latitude off GPS Latitude on 10 38 3 298 38 3 311 38 737311 20 38 737298 38 737298 38 737312 30 38 737298 38 737332 38 737307 40 38 737298 38 737341 38 737315 50 38 737298 38 737257 38 737309 60 38 737298 38 737299 38 7
65. ery pack Live video from a single board camera was transmitted from the plane to a ground station and was recorded on VHS video The sensor platform also included a digital 2 MegaPixel camera with the capacity to store 50 images The RPV weighed 3 4 kg making it light enough to hand launch and it was able to withstand belly landings The simplicity of the plane allowed for easy transport and on site data review The platform used by Hardin and Jackson 13 in 2005 was designed to include remotely controlled aircraft with a flight stabiliser a 35 mm camera and a GPS receiver Upon landing the GPS data was downloaded yielding the plane s vertical and horizontal positions and velocity The photograph locations were found by following the GPS tracks As part of the Global Dust Program the United States Geological Survey USGS designed a UAV to identify micro organisms that can survive long range atmospheric transportation by desert dust clouds The study used a one quarter scale Super Cub aircraft with a wingspan of 2 5 m and nitro engine com bination capable of carrying 14 kg for one hour duration at an altitude of one kilometre 14 The UAV telemetry included real time positioning autonomous scientific instrumentation control autonomous flight and ground control and a lightweight precision vision system In 15 a modified radio control RC aircraft equipped with a GPS receiver and a digital camera was proposed to conjunction with automated
66. ery t seconds 2 Pulse Width Modulation is a technique used to encode a message in a pulsing signal where the average value of voltage and current is controlled by turning the switch between supply It used to relay data in the form of a varying pulse width The way data is relayed to a servo for instance is the time the pulse is on 3 Frequency Shift Keying FSK is a frequency modulation scheme in which digital information is transmitted through discrete frequency changes of a carrier wave 21 It is desired that the UAV is built out of commercial off the shelf COTS solutions and the market offers a variety of radio link options in a wide spectrum of frequency bands Manufacturers usually provide a whole set of parameters for their links such as e Transmitting Frequency The usable frequency spectrum extends from 3 Hz to 300 GHz which is split into standardized regions As frequency increases the signal is prone to be absorbed by physical objects atmospheric moisture trees buildings etc hence the need for more power to 14 make up for signal loss For constant power the range decreases with the increase in frequency due to the increase in signal loss This energy transfer to physical objects is similar to the one behind microwave ovens which operate in 2 45 GHz that transfer the transmitted energy to water molecules 22 Another factor affecting terrestrial communication range is the tendency of low frequencies to follow th
67. ess of the International Council of the Aeronautical Sciences St Petersburg 2014 18 Piotr Rudol Increasing autonomy of unmanned aircraft systems through the use of imaging sen sors Ph d thesis Link pings universitet 2011 19 Autoridade Nacional de Comunica es Quadro nacional de atribui o de frequ ncias Accessed 2014 11 27 20 Autoridade Nacional de Avia o Civil Seminario sobre regulamenta o de RPAS February 2015 21 D Grini Rf basics rf for non rf engineers MSP430 Advanced Technical Conference 2006 22 L Barclay Propagation of Radiowaves Electronic Waves Series 502 2008 ISBN 13 978 0852961025 23 D M Pozar Microwave Engineering John Wiley and Sons Inc 2012 24 If the lower the frequency the longer the range why not building for example a 72mhz Irs system Information retrieved from private e mail conversation with Patrick Mikkelsen and Steven Friberg Accessed 2015 02 24 25 Harmonics and frequency planning technical breakdown of tslrs ezuhf dragonlink https www youtube com watch v RFC9PDTjJ4E Accessed 2014 02 26 26 Sba responds to scherrer uhf https www youtube com watch v Q4V20e7PCg0 Accessed 2014 02 26 27 Scherrer UHF Long Range System Manual for tx700 November 2013 28 H Chao Y Luo L Di and Y Chen Fractional order flight control of a small fixed wing uav controller design and simulation study In Proceedings of the 2009 ASME Internati
68. f this thesis Finally would like to thank Maria Ana Silva who makes hard work easier every day vi Resumo Ve culos a reos nao tripulados UAV nasceram no sector militar e evolu ram de forma exponencial nos ltimos anos devido ao facto de serem vistos como uma abordagem barata e dispensavel a miss es de alto risco secretas ou politicamente sens veis Estao de facto a ganhar uma m reputacao mas um n mero cada vez maior de industrias civis est a tomar proveito desta evoluc o tecnol gica para um bem maior Sao uma abordagem vi vel em detec o e preven o de fogos opera es de salvamento agricultura de precis o ou jornalismo Nesta disserta o abordada e analisada uma solu o para pilotagem remota de um destes ve culos para aplica es a longas dist ncias utilizando equipamento comercial Para o sucesso desta disserta o foram definidos e explicados objectivos de miss o e requisitos para o ve culo O design final sujeito a testes em ambiente controlado e ensaios em voo e a performance do UAV assim utilizada para avaliar as solu es iniciais e prop r uma configura o final para um ve culo aereo n o tripulado capaz de percorrer longas distancias sem perder recep o de controlo e transmiss o de v deo A plataforma em causa est dividida em tr s sistemas principais o controlo remoto o sistema de v deo e o r dio de telemetria que juntos ligam o UAV esta o de terra Como forma de ava
69. for multipath fading propagation and polarization losses radiation pattern null and signal obstruction 66 Currently the available equipment does not allow the testing of all these proposals since there is only one transmitter available and there is no diversity equipment in the video system and so the proposed solutions from Table 6 2 that involved more than one video equipment or diversity system are not tested However this table can be used as a future reference Secondly it is important to state which parameters will be varied for this test e Distance e GCS antennas e UAV antennas With these four antennas it is possible to make four different antenna configurations in each check point Thirdly a location that provides the same range as for the communications link is selected The location of Cascais was found to be too noisy for an analogue video system for the RC link was a digital one which is less affected by noise So Fig 6 6 shows the new place of choice in which the testing took place Baleal Peniche 50 Figure 6 6 Points along the coast where the experiment took place In this test are shown the differences between vertical and circular polarisation a higher and a lower gain antenna and how these different solutions can solve issues from Table 6 2 The video sequences were shown to a group of 4 random people who according to MOS in 67 compared the various sam ples Lastly for the testing of pr
70. fore has been around for a while Also a light airframe will theoretically allow better results B 1 1 Weight Distribution An aircraft can perform a steady flight if the resultants of the external forces and moments about the mass center both vanish which implies the pitching moment to be zero If an aircraft is longitudinally stable a small increase in angle of attack will cause the pitching moment on the aircraft to change so that the angle of attack a decreases Similarly a small decrease in angle of attack will cause the pitching moment to change so that the angle of attack increases A non zero pitching moment Cm will cause a rotational acceleration in the direction of the unbalanced moment The static stability is determined by the sign and magnitude of the slope It can then be said that Cm must be positive and negative if the airplane is to be in a condition of stable equilibrium 72 lt has been found both experimentally and theoretically 72 that if the aerodynamic force is applied at 25 of the chord from the leading edge of a rectangular wing the magnitude of the aerodynamic moment remains nearly constant even when the angle of attack changes This location is called aerody namic center AC To calculate the mean aerodynamic center of a tapered wing equation B 1 may be used LENEA MAC Croot 2 3 CEDE TEM B 1 where A is the wing s taper ratio o Croot the root chord and c the tip chord The c
71. gation Linear dace IR Elliptical Figure 3 6 Types of propagation directions of an antenna 36 Gain Another important parameter that characterizes an antenna is the gain or more correctly its directivity 34 An antenna is a passive element it has no gain since it does not amplify the signal What it does is it concentrates the radiation to a certain area of the space The higher the gain the narrower the 22 beam of radiation Using a moderate gain patch antenna 8 dBi the radiation is concentrated in a beam of about 60 covering a large area of flight To increase the flight distance more gain is needed This can be done using a 24 dBi parabolic antenna in which the beam width will be only 8 implying that the antenna has to be kept fully focused on the plane 22 3 4 1 Tx Antenna Testbed Selection High gain antennas for point to point communication links and UHF reception are usually Yagi Udas since parabolic dishes only become practical at the top end of the UHF band 22 The ground station antenna will have to cover a wide range Also the bandwidth used for transmitting radio control will be between 430 and 490 MHz amateur purposes This is possible to do without spent a great amount of energy It is just necessary the right antenna A directional antenna concentrates all its energy into one direction allowing the same energy to go much further Regarding the gain of the antenna when it is said that it is a high g
72. gnals are constantly changing electromagnetic waves which can be influenced by external electromagnetic fields Digital signals are electrostatic pulses of a fixed amplitude They resist external fields because the pulses are either fully on or fully off 22 This LRS has been used since 2008 in the most diverse applications with proven results The Tx unit shown in Fig 3 3 a samples PPM frames from a standard remote control Tx unit from 4 to 12 servo channels and encodes this data digitally SN EMA en PMA ALA E L m E y in Lt E La E J 12 CH RSSI OUT RX LR 7 00 TSLRS COM MECA a Scherrer Tx700 b Scherrer Rx700 Figure 3 3 Thomas Scherrer long range RC system 27 The Rx unit shown in Fig 3 3 b decodes the data and generates the desired up to 12 pulses giving a jitter free system known from all pulse code modulation PCM systems At the same time this system uses a multi frequency hopping FHSS making it more immune to jamming The diversity system which is choosing the best receiving antenna from having two connected on the Rx removes blind spots when the angle from the plane to the ground station changes from for example a banking manoeuvre if one of the antennas is placed horizontally and the second vertically It operates through the UHF band 433 MHz to 440 MHz has a maximum radiated power of 2 W and has a Receiver Signal Strength Indication RSSI analogue output pin that proves
73. he display monitor To set it up it is just a matter of hooking it up to the flight controller and connect it between the FPV camera and the video transmitter link 12 V from a LiPo battery feeds directly the FPV camera and video transmitter It also feeds the analogue line by a 5 V voltage regulator avoiding noises from servos attached to the APM The Minim OSD is priced at 40 Features from the MinimOSD can be seen in Table 4 2 47 The RangeVideoOSD RVOSD is a stand alone on screen display OSD and flight controller This is already the fifth generation which means there has been plenty of time to correct and improve this concept The RVOSD enhances the overall flight experience through a continuous stream of information relating to the aircraft such as position speed altitude distance from home and battery level It performs the functions on a flight controller and an on screen display in one compact package being actually lighter than the APM combination it weights 29 g and the APM OSD weights 35g It contains four integrated sensors two gyros an accelerometer and a barometric pressure sensor that working together provide precise control of the aircraft under many different scenarios and even allowing six different modes The RVOSD is priced at 240 Features from the RVOSD can be seen in Table 4 2 33 The EzOSD module may be used stand alone and will offer navigation and basic voltage measuring capabilities The 100 A current sens
74. he maximum range is 7 km 92 The limit in range for the video system is determined by the helical skew configuration at 7 km The last tried checkpoint was at 9 km where the connection did not show any signs 10 q artical c vertical Vertical c skew Overall Image Quality Helada c Vertical Heliaxtal c Skew Distance rr Figure 6 8 Video Quality affected by propagation loss Regarding the video issues discussed in Section 4 2 as the distance between antennas grew their presence became stronger and stronger Tables 6 3 6 4 and 6 5 illustrate the effect of different antenna configurations on signal propagation issues where V v H s stand for vertical antenna mounted at the GCS vertical antenna onboard helical antenna on the GCS and skew planar antenna mounted onboard respectively They also show how much these issues degrade the video link as a function of the distance This classification was also attributed using a mean opinion score same as the rate of image quality for propagation loss The minus signs indicates that the image was beyond annoying Inclination Distance km V v Vs H v H s 0 6 7 8 9 9 2 4 8 9 9 3 4 3 9 10 4 2 1 8 9 6 8 8 7 5 9 E Table 6 3 Inclination with different configurations and distances Regarding inclination the antenna configuration that is most affected is clearly the monopole an tennas This is because when the GCS is always in a verti
75. he same 48 In conclusion although using a directional the Yagi antenna will give double the range of an omni directional monopole a new factor emerges the antenna has to be manually oriented Also the use of more than 0 5 W as output power is only justified at an 8 km distance The estimates that were done are very conservative due to the fact that these tests are performed 2 m above the ground When flying at 1000 m altitude better results are expected 6 2 Testing of the Video Link System 6 2 1 Test Design The objective of this test is to evaluate the influence of the type of antenna used for the video link in its quality and range as shown in Figs 6 5 a Vertical GCS Vertical UAS b Vertical GCS Skew Planar UAS a c Heliaxial GCS Vertical UAS d Heliaxial GCS Skew Planar UAS Figure 6 5 Video link system configurations For these tests a small platform was built using the following equipment e Partom 1 2 GHz 850 mW transmitter Standard omnidirectional with linear polarization antenna e Partom receiver with the same omnidirectional with vertical polarization antenna Circularly polarized skew planar wheel antenna Circularly polarized helical antenna The first step when testing the video system is to understand the different issues that weaken the video link quality and then to replicate them in order to determine if any adopted solution corrects those 4
76. heoretically a longer range all LRS sys tems are sold for 433 MHz This because the law does not allow enough bandwidth per channel to encode digital data and also because high enough emitted output power is not legal 24 In the following paragraphs it will be presented a market study on different long range systems that could be implemented There are many options to choose from and these LRSs were considered because of their popularity within the community This means there are many reviews and experiments 25 26 are just a couple of examples about them which facilitates the selection process In order to choose a proper long range system it is important to retain the following requirements e Phase Noise of the Transmitter e Effective Radiated Power of the Transmitter Sensitivity of the Receiver Estimated Range e Price Based on the requirements itemized above four systems are compared for radio control and in the end the one with better price quality ratio is chosen The systems chosen based on popularity are the DragonLink the EZUHF the OpenLRS and The ThomasScherrerLRS First the systems were compared on the harmonics that are represented in Table 3 1 Scherrer 25 EZUHF 25 DragonLink 25 OpenLRS 26 Binded Frequency MHz 433 433 433 433 Output Power dBm 27 27 27 27 3rd Harmonic Frequency MHz 1296 1296 1296 1296 Phase Noise dBm 64 48 50 80 Table 3 1 Comparison of phase noise and output power of
77. ies 3 3 Telemetry Radio The telemetry radio which is a supplement to the APM autopilot was acquired because it provides an air to ground data link between the autopilot and the ground station computer lt works as it is a replacement for the USB connection to the computer This radio shown in Fig 3 5 will allow real time data from the UAV Since it produces 100 mW minimum of output power it can be said that it is a quiet equipment to the on board receivers lts drawback is a rather limited range of 2 km A 3 7 to 6 V voltage range allows a direct connection to the UAV not requiring a voltage regulator lts main specifications are summarized in Table 3 5 3 4 Radio Control Antennas Any radio transmission occurs at a certain frequency depending on the propagation of speed waves through the air The geometry of the antenna is based on taking advantage of resonances so that their 20 Table 3 5 General specifications of 3DR telemetry radio 3DR Telemetry radio Frequency 433 MHz output Power 100 mW receiver sensitivity 117 dBm Communication Full Duplex Protocol Framing MAVLink Figure 3 5 Telemetry Radio from 3DR Robotics FHSS Open source firmware Configurable Receive Current 25 mA physical dimensions are closely related to the wavelenght of the signals For practical purposes this implies that an antenna generally will be bigger when designed for lower frequencies It is possible to divide antennas for UAS into gro
78. increases the usable operating area of the UAV For this telemetry readings and a video transmission will take part of the onboard equipment This way an example of an airborne system is shown in Table 2 1 and Fig 2 2 Equipment Description Actuators Small mass produced servomotors used for radio control Engine and propeller Machine designed to convert one form of energy into mechanical energy Battery Converts stored chemical energy into electrical energy Video Transmitter Tx Transmits audio and or video signals wireless from one location to another Video Camera Captures video that in this case becomes the eyes of the pilot RC receiver Rx Receives radio control signals from a source and processes them to the actuators Flight Controller allows the operator to turn any vehicle into fully autonomous capable of performing programmed GPS missions with waypoints Transmitting Antenna Radiates the energy from the transmitter as electromagnetic waves Receiving Antenna intercepts some of the power of an electromagnetic wave in order to produce a voltage at its terminals that is applied to a receiver to be amplified and interpreted Table 2 1 Airborne equipment necessary for RPV operations Antenna Figure 2 2 Airborne equipment necessary for RPV operations 2 1 2 Ground Station The control station is based on the ground and it is the control centre of the operation and the man machine interface It is usually the p
79. ing short range flight test a 68 7 2 Weather conditions during the longer range flight test 72 A 1 List of parts needed to build an antenna tracker 71 88 B 1 Main specification of the selected airframes o 91 B 2 Skywalker data for the calculation of the center of gravity 93 B 3 Measured specifications from the Skywalker Airframe 95 B 4 Intermediate steps for calculation the Base Drag Coefficient 96 B 9 0OS38 10SPECS ui 24 za DEE mr ren RRA Sea a 96 B 6 Experimental Data for each propeller using the same OS engine 97 Xvi List of Figures 1 1 1 2 2 1 2 2 2 3 2 4 3 1 3 2 3 3 3 4 3 5 3 6 3 4 1 4 2 4 3 4 4 4 5 4 6 4 9 1 3 2 9 3 9 4 3 9 9 6 9 7 9 8 UAVS NEDIN tarmes 2 o ooo vise 2 2 2 23 24 dede A ds 1 UAVS wildfire aiding Al cari ie A it aaa de 2 UAS Funcional SUCIU sas ani cir are ee dodo Qu ea GRE e oe c Bm a E 8 Airborne equipment necessary for RPV operations 9 Ground station equipment necessary for RPV operations 9 UAS coverage assuming a 100 km range along the portuguese coast 11 Block diagram showing the radio control RC sub system 0 4 13 Basic building blocks of a RF system 21 o a ee eee 14 Thomas Scherrer long rang
80. ion parameters from Section 6 2 and the different video samples from each checkpoint video quality was evaluated rating colour contrast borders and movement continuity just as in Section 6 2 Regarding propagation losses Figs 6 12 illustrate how video quality is affected by the distance between antennas and the difference between using only the video system or all the systems together according to the subjective opinion data gathered Smearing Flickering tov Continuity Borders Contrast Colours 10 12 a Video Quality according to the presented parameters b Video Quality when added the APM and the Mini in 6 2 mOSD Figure 6 12 Ground station interferences and outlook Bauen ps 35 40842 a EIA eee 5 263451 a GCS turned off b GCS turned on Figure 6 14 Video System coupled with the onboard RC equipment As it was done in the video alone quality test an overall parameter was built based on the six parameters from Figs 6 12 and the result was compared with the overall video quality of the video system alone which can be seen in Fig 6 15 As it can be seen the video quality of the UAV becomes degraded when compared with the results of the UAV from Fig 6 12 At first it was assumed that this was due to the interference of the control 59 Video Stand Alone Overall System o gt Overall Video Quality s 4 Distance km Figure 6 15 Comparison between the
81. it is provided some insights on why image quality assessment is so difficult by pointing out the weaknesses of the error sensitivity based framework Equation 4 1 from 40 states that the only thing it can state is that if the received power is below the sensitivity value of the receptor a connection is not possible The contrary is not necessarily true but 34 typically if the received power is at least 20 dB above the sensitivity limit 41 it is likely that the video has a good reception quality P Ke A il 4 1 P G Gr a Rad In 61 a new approach on video quality metric based on light adaptation luminance and chromatic channels spatial and temporal filtering spatial frequency channels contrast masking and probability Summation dynamics of light adaptation and contrast masking is attempted It applies the metric to digital video sequences corrupted by compression artefacts and compared the results to quality ratings made by human observers Although the results show improvements when compared to others they also show systematic failure of prediction Since quantitative metrics for measuring video quality are still a long way from precise the chosen method of evaluation for this dissertation is the subjective quality measurement Mean Opinion Score MOS that has been used for many years and is documented by the International Telecommunication Union ITU in 62 This method consists on using the human eyes to simply eval
82. itive response from the RC commands the stabilise box was checked This would order the camera to respect and follow the attitude defined by the accelerometer In this test the tilt responded with success However the pan would only respect a heading that pointed North since the UAV was laying on the ground After this test it was decided that the tilt was ready for a flight test However the pan did not respond well to the test and could cause disturbances to the system It is suggested that the autonomous tracking is used on a second camera gimbal a second video system whose purpose is not to pilot the UAV but to monitor the surroundings 63 6 5 Testing of the Energy Consumption 6 5 1 Test Design The components electrical energy consumption is one of the elements that limit the range and endurance of the UAS Depending on how much time the batteries last the UAV will be able to fly longer or shorter distances In this setup both components from the ground station and the onboard use batteries for energy and so it is important to do an estimate of how much they consume and how long they last Thus the objective for this test is to do an estimate on the consumption of each component and for this two experiments will be made the consumption of the RPV ground station receiver DVR and screen and the onboard video transmission Tx OSD and camera As for the control system both ground station and onboard will be tested Only a sim
83. k Pa a i i an A Pu an i C e i i ns r E is yr m a 7 k i Ir i E E kE Ee ior y a x 1a do mn 150 FA 150 a Directivity chart for the A430510 b A430510 antenna figure c RC system Thomas Scherrer wire antenna Figure 3 7 Long range RC system 37 27 23 3 4 2 Rx Antenna Testbed Selection Omnidirectional UHF antennas used on mobile devices are usually short wires or rubber ducky anten nas Higher gain omnidirectional UHF antennas can be made of collinear arrays of dipoles and are used airborne The type of antenna that comes standard with the Thomas Scherrer Receiver is linearly polarised Figure 3 7 c illustrates the antenna that comes with the Scherrer system However simple as the antennas is the ones which came standard were too small to take advantage of the diversity capabilities of the receiver let alone be as separate from the video Tx as possible For this reason two new antennas were built They are just the same as the one from Fig 3 7 c but extended This was done making use of 88 This way one antenna was placed on the left wing making it horizontally polarized and the other on the vertical tail making it vertically polarized 3 5 Estimation for the Communication Link Systems From 39 the IEEE 802 11 defines a mechanism by which RF energy is to be measured by the circuitry on a wireless link This numeric value in an integer with allowable range of 0 225 called the Received
84. k Quality from the telemetry radio which is read on the Mission Planner HUB The telemetry radio was proven to be the weakest link in the whole system mainly because of two reasons the antenna used a linearly polarized monopole and the operating power 100 mW As it can be seen in Table 6 6 the link shows a strong connection in the first two checkpoints but rapidly loses signal after 800 m However it is noteworthy that a 90 inclination almost does not affect the strength of the link because in the video link the monopole antenna is strongly affected by its inclination 6 3 2 Testing the Interference between the Telemetry Radio and the TSLRS For this test it is also used the same route from Fig 6 3 and it is composed by the same equipment as in Subsection 6 3 1 First the receiver is included on the onboard equipment and the standard monopole antenna is connected Secondly the monopole is replaced with the Yagi to evaluate the quantitative difference This experiment is done in two different points at O m a desk test and at 360 m Table 6 7 represents the interference between the two systems As it can be seen the TR triggers no interference on the LRS due to its low output power of 100 mW while the LRS transmits a minimum of 500 mW Checkpoint LRS on TR touch monopole LRS on TR touch Yagi TR on the LRS 1 from 99 to 60 from 96 to 54 X 2 from 97 to 20 from 91 to 30 X Table 6 7 Influence of the LRS on the telemetry
85. latform in which the mission is pre planned In a similar way via the communications down link the aircraft returns information and images to the ground station operators This information may include data from the payloads status information of the sub systems and position information This way an example of a ground station is shown in Table 2 2 and Fig 2 3 Equipment Battery Video Receiver Rx Video Recorder DVR Radio Control Transmitter Tx Display Monitor Transmitting Antenna Receiving Antenna Description Converts stored chemical energy into electrical energy Receives audio and video signals from a number of sources and process them to drive loudspeakers and a display Records video in a digital format to a memory storage unit Generates a radio frequency alternating current which is applied to the antenna When excited by this alternating current the antenna radiates radio waves Electronic visual display for video system Radiates the energy from the transmitter as electromagnetic waves Intercepts some of the power of an electromagnetic wave in order to produce a voltage at its terminals that is applied to a receiver to be amplified and interpreted Table 2 2 Ground station equipment necessary for RPV operations Ground Station Video DVR Display Rx recorder Monitor LRS Tx Rx Antenna Zu cr Figure 2 3 Ground station equipment necessary for RPV operations The launch equipment can take the fo
86. le 4 3 Advantages and disadvantages of different frequency bands Regarding the power of the video transmitter this will be listed in mW and it is not recommended to go over 1 W because although it will give a beiter range this will not be a proportional relation and it will most likely enable interferences with the GPS and the radio control The large majority of RPV video Tx 91 also allow choosing between several different transmitting channels within its specific frequency band which allows the user to tune the video system for the best image transmission if one channel seems less noisier than the others Partom Lawmate DJI Lightbridge Working Frequency GHz 1 2 1 2 2 4 Tx Output Power mW 850 1000 100 Rx Sensitivity dBm 85 85 101 Weight Air system g 21 30 71 Video Encoding PAL or NTSC PALorNTSC PAL NTSC or HDMI Operating Current mA 245 350 700 Antenna Plug SMA SMA MCX Price 83 137 1400 Table 4 4 Main specifications for each video system Rx and Tx 49 50 51 There are two types of video systems here presented digital and analogue Table 4 4 presents two analogue systems the Partom and the Lawmate and one digital the DJI Lightbridge Beyond the difference in output power and consumptions the digital system allows a much more effective transmission it is less affected by interferences and less susceptible to wobbling 22 As it could not be a system with much a higher quality is much more expen
87. liar o desempenho do sistema de controlo foi utilizado o par metro indicador de for a de sinal recebido RSSI enquanto que para avaliar o sistema de v deo foram utilizados par metros como perdas por propaga o polariza o e obstru o Apesar das dificuldades em definir um alcance de voo m ximo do sistema global a solu o encon trada provou ter utilidade para aplica es de longo alcance Palavras chave RPV UAV longo alcance v deo controlo remoto vil vill Abstract Unmanned Air Vehicles UAV made their way through the military sector They have evolved expo nentially in the last decade due to the fact that they are seen as a low cost and expendable way for highly dangerous secret or politically sensitive missions They are in fact getting a bad reputation but a large number of civil applications are taking advantage of these technological advancements for a greater good Sensor technology data processing hardware and software algorithms have made the Un manned Aircraft System UAS a highly feasible approach in fire detection rescue operations precision agriculture maintenance or journalism A solution for RPV using commercial off the shelf COTS equipment is presented and analyzed An Unmanned Air Vehicle UAV design was proposed and evaluated through not only in a controlled environment but also flight testing The performance of this UAV was then used to evaluate the choices made and purpose a definite
88. long its coast with the GCS installed at the Marina of Cascais and the portable device consisting of the RC componenis to be later installed in the UAV travelling along the 8 46 kms Including the 0 km mark the measurements took place in seven discrete places as labeled in Fig 6 3 The test proceeded the following steps 1 Mount the Ground Control Station which includes the Tx700 the Graupner mc 24 and the battery and the portable configuration which includes the ardupilot Rx700 servo Power Module battery and PC 2 Test the system at 0 km and turn off both batteries 3 Go along the coast from Fig 6 3 turn on the equipment at the first checkpoint measure the RSSI level and move the servo to its extreme positions 4 Turn off the equipment change the transmitter antenna from monopole to Yagi and turn on the equipment measure the RSSI level and move the servo to its extreme positions 5 Repeat steps 3 and 4 for checkpoints 2 to 10 The experience stops when the servo no longer responds continuously 6 1 2 Test Results Distance km 3 95 6 97 8 32 0 5W Y Y X X X X Monopole 1W Y Y X X X X 2W Y Y X X X X 0 5W Y Y J Y X X Yagi 1W Y Y Y Y Y X 2W Y JV Y Y Y Y Margins Contin Margins Contin Margins Contin Mov Mov Mov Table 6 1 Output behaviour of the servo in function with the distance Table 6 1 shows how the servo behaved in terms of movement continuity Contin Mov and reaching its en
89. mOSD and powered through the Easy FPV board When connecting a 3S LiPo battery to the Easy FPV board it will not only power the Video Tx but also one side of the MinimOSD and the camera Table 5 4 expresses the connections from the MinimOSD through the Easy FPV board to the Video Tx The auxiliary Figure in the table shows the shape of the Easy FPV board A detailed scheme of the referred connection is shown in Fig C 1 from Appendix C Portnr MinimOSD Miniboard input Port Miniboard output FPV Tx 1 Vout Vout 1 Yellow Video in Video in 2 12V 12V 2 Red Power 12V Power 12V 3 GND GND 3 White Audio in Audio in 4 Black GND GND Table 5 4 Connections from the MinimOSD through the miniboard to the video Tx As it was done in SubSection 5 1 2 Fig C 1 from Appendix C shows how the RPV system was connected for the realization of this dissertation 5 2 Setup of the Ground Station 5 2 1 Control Station Setup The first thing to do when using a long range system is to bind the remote controller with the LRS system In this particular case a Graupner mc 24 remote controller was coupled with a Scherrer transmitter While the mc 24 works with a 2 4 GHz transmitter the Scherrer Tx700 will make the controller work with a 433 MHz one which allows the UAV to be controlled at long distances The binding process is described in the user s manual 27 so there is no need to repeat it in here However there is an exception with the Graupn
90. mbal c Video loss at 2 03 km from the GCS tenna towards the UAV 3 to do a terrain recognition 4 5 d Image recover after reorienting He e UAV performing a 61 manoeuvre f Signal loss at short range due to lical antenna 7 with any image conflict 8 antenna orientation 9 Figure 7 14 Remarks from pinpoints 3 to 9 towards the UAV Regarding pinpoint 5 the UAV is now 2 03 km away from the Ground Station and the video starts to get weak flickering and smearing appear as seen in Fig 7 14 c The pilot recognises the situation and moves 100 m North towards pinpoint 6 and that is where the video link improves significantly as seen in Fig 7 14 d Pinpoint 7 is where the flight range achieves its maximum value of 2193 m The video link is now getting smeared and the pilot decides to return home because moving the antenna might mean losing the link entirely This does not mean the maximum range of the video system is 2 km it just means that it gets harder to reposition the antenna without knowing the exact direction the UAV It is easy to come to the conclusion that orienting the antennas manually is not advisable for long range flights The use of an antenna tracker is definitely more advisable Pinpoint 8 is yet another confirmation that the circular polarization was a good choice as seen in Fig 7 14 e The UAV is now almost 1 km away performing a banking manoeuvre of 61 and the video link is n
91. milli 107 u micro 10 Table 3 6 Frequency Spectrum up to 3000THz 22 Antenna Polarization There are two special cases of polarization linear polarization and circular polarization In a linear polarization the electric field of the radio wave oscillates along one direction this can be affected by the mounting of the antenna but usually the desired direction is either horizontal or vertical In circular polarization the electric field rotates at the radio frequency circularly around the axis of propagation 22 Itis best for the receiving antenna to match the polarization of the transmitted wave for optimum reception Intermediate matchings will lose some signal strength but not as much as a complete mis match A transmission from a circularly polarized antenna received by a linearly polarized antenna or vice versa entails a 3 dB reduction in signal to noise ratio as the received power has thereby been cut in half 22 Fig 3 6 shows the different possible polarizations for a propagation When the field remains in a particular direction the wave is considered to be linearly polarized In the case of circularly polarized antennas the electric field rotates as it travels along Elliptical polarization on the other hand is the polarization of electromagnetic radiation such that the tip of the electric field vector describes an ellipse in any fixed plane intersecting and normal to the direction of propagation 22 direction of propa
92. mponents will support both types With that said the camera is usually the one video component in the system that is one or the other PAL is the primary analogue video system used in Europe and does provide better resolution compared to NTSC but has a slower frame rate 44 28 Many of the popular CCD FPV cameras used today make use of the 30 mm lens Most cameras also allow to thread different mount lenses into the lens body tube to change the field of view FOV or even increase the light gathering capabilities making them very adaptable The majority of these small cameras come with a standard 3 6 mm focal length lens giving about a 90 FOV The lower the focal length number the wider the FOV fish eye effect The higher the focal length number the more zoomed in the image will appear A 3 6 mm about 90 field of view is a good compromise in all aspects However in this aspect it is only a matter of preference some Since this camera will be used just for flying and not for any particular application the 3 6 mm lens will give a wide image with fish eye effect Regarding camera definition within the 500 and the 700 TVL TV lines of resolution is what the average pilot uses Of course the more resolution the camera has the more costly it will be Spec Type Imaging Device CCD TvLines 520 Encoding PAL Size 25x25 mm 1 3 Consumption 50 mAh Voltage 12V Weight 26 9 Price 76 Table 4 1 Kx 181 CCD Sony Camera char
93. n in Fig 7 4 it is seen that the diversity capability of the TSLRS Rx is properly effective since for example at minute 1 40 1 the UAV is manoeuvring with a roll of 39 and the RSSI reads 85 120 100 RSSt 20 y Roll 1 0 00 24 3 38 4 48 6 00 7 12 B 24 3 36 10 48 Time min Figure 7 4 RSSI versus the Roll of a certain manoeuvre 7 1 2 Video Link Quality The same flight from Subsection 7 2 1 is analysed but now from the point of view of video quality Just as was done with the Yagi the helical was not moved during the whole flight with Fig 7 5 showing the directivity limits of the helical antenna which is 60 It is noticeable that the UAV did not get outside those limits Despite being inside these limits there are still some glitches and images distortions It was found that the image would distort mostly around the telemetry data As in Section 6 2 this was found to be due to the coding behind the MinimOSD since the coupling of the video transmission with the MinimOSD degrades the video Fig 7 7 exemplify this issue As for glitches due to banking this was found to have two sides the manoeuvre with maximum bank angle 39 roll seen in Fig 7 6 mentioned in Section 7 2 1 does not show any kind of glitch or distortion However lingered banking manoeuvres would somehow distort the image This again can be 69 Figure 7 5 Overall flight data for a short range flight 29 48249 2 70
94. nna is consuming too much energy lt was tested and 64 Component Total Test Time min Current mA Energy mAh Avg Input Power W Video Rx Heli 45 770 825 9 43 Video Rx Monopole 45 770 825 9 25 Video Tx Skew 60 3100 3069 35 81 Video Tx Monopole 60 3100 3060 35 81 RC Rx Wire 60 240 245 2 96 RC Tx Yagi Low 30 220 128 6 09 RC Tx Yagi High 30 710 370 6 09 RC Tx Monopole Low 30 650 307 6 09 RC Tx Monopole High 30 222 900 5 61 Table 6 18 Sub systems testing in energy consumption the antenna was not in short circuit The reason why this was happening was not found it was tested if the antenna was in short circuit Assuming that each battery is equally charged at the beginning of each testing the video reception is the one that spends the most amount of energy both in the ground station and onboard Onboard the video system is mostly responsible for the energy consumption maybe due to the fact that the video transmitter is very inefficient since it loses too much energy from heating From this sub systems testing it is possible to conclude that with a 4200mAh battery it is not recommendable to perform RPV for more than one hour This value will obviously be drastically reduced by the electric engine at full throttle a 10 x5 blade will drain the battery in little over five minutes see Table B 6 A more accurate estimate for total system consumption can be done with actual flight tests 65 66 Chapter
95. no need of using the telemetry radio that had a limited output power of 100 mW The design from Alexander Greve was chosen because this antenna tracker working properly will have the same range as the video system and not the range of the the telemetry system adaptation 87 A 2 Long Range Design All the needed parts are commonly available which is a plus because they can be bought online or ina local store The list of parts is summarized in Table A 1 1 PCB board 5x7 cm 2 5 cm hole spacing 1 Resistor 270 K9 1 voltage regulator UA 7805 2 Resistors 22 KQ 1 voltage comparator LM393 6 Resistors 15 KQ 1 Operational Amplifier OpAmp LM358 2 Resistor 2 KQ 2 555 timer NE555N or NE556N 1 resistor 390 2 2 electrolytic capacitor 1uF 2 Diode N4148 1 Capacitor 4 7 uF 1 Heatsink TO 220 1 Capacitor 1 uF 1 Standard size servo 2 Potentiometers 100 KQ 3 Video Rx 1 Potentiometer 1 Mega 2 3 directional antennas Table A 1 List of parts needed to build an antenna tracker 71 Figure A 1 shows the tracker control board schematics Rs Si Butter RSS 1 in O 100K Signal comparator 12 15K RSSI 2 in e n SK G IH w o 9 3 ml o 2 o lt e o 1 555 Timer NESSSN or similar Figure A 1 Tracker board schematics 71 The RSSI pin will be used to determine the position of th
96. oduced is too high it will interfere with the video system that works on the same frequency of the RC s hamonics The main causes for video link interfering with other systems are itemized below e Video Tx output power e Video Tx antenna position As for ground station interferences in the case of the TSLRS in binding mode 0 5 W at 432 3 MHz the 37 harmonic appears at 1296 9 MHz with 65 dBm 25 Table 6 8 shows how these two frequencies can interfere The right frequency will provide the best video quality possible using these two systems 3rd harmonic All signals contain harmonic frequencies 1296 9 Some waveforms contain large amounts of Rx Frequency energy at harmonic frequencies Scherrer 3rd harmonic 1080 1120 1160 Bad designed transmitters emit more Partom 1200 1240 1280 energy at harmonic frequencies 1320 1360 Table 6 8 Principle cause for RC Tx interference with video Rx Summarizing for this experiment it is important to see if all the systems are compatible and find out their limitations For that the experiment will be divided into two sections ground station interferences and onboard interferences 6 4 1 Ground Station Interferences RC Tx with Video Rx On the ground station there is a video receiver and a radio control transmitter In terms of interfer ences there is only one way in which they can happen the RC transmitter may interfere with the video 57 receiver The objective of this tes
97. omes helpful when features besides the usual four servos configuration are added for example when using a camera gimbal onboard or when having an autopilot that has more than one flight mode Its most important features are 1 six free configurable flying phases with pre configurable rudder positions and variable switching time 2 Up to 16 full free configurable switches 3 Up to eight full free configurable control switches 3 Trim travel reduction 4 Servo speed configurable for every servo or control 5 six programmable clocks 6 Can be used as teacher student transmitter 7 It has four modulation systems SPCM 20 10 channels PCM 20 10 channels PPM18 9 channels PPM24 12 channels All the mentioned features will allow a more complex UAS where functions that were not thought at the beginning and start to appear as the project grows For these reasons the Graupner mc 24 remote controller was selected 3 1 2 Receiver The receiver Rx interprets the signals from the transmitter and sends them out ot the servos The receiver must match the transmitter to work properly They must be both of the same type band and channel settings Most receivers operate at 4 8 V or 6 V Some have a battery eliminator circuit allowing the connection of a 7 2 or 8 4 V a main battery on an electric model into the receiver The standard voltage in use is 6 V equal to a four cell alkaline holder and since any of the receiver s channels will accept power
98. onal Design Engineering Technical Conference Computers and Information in Engineering 2009 29 Duarte Lopes Figueiredo Autopilot and ground control station for uav M s thesis Instituto Superior Tecnico October 2014 30 H Chao Y Cao and Y Chen Autopilot for small unmanned aerial vehicles A survey International Journal of Control Automation and Systems pages 3144 3149 August 2007 doi 10 1007 s12555 010 0105 z 82 31 APM 2 6 Autopilot User Manual 3DRobotics March 2013 32 Pixhawk Autopilot User Manual 3DRobotics March 2014 33 On Screen Display Autopilot for Model Airplanes User Manual RangeVideo August 2012 34 C A Balanis Antenna Theory Analysis and Design John Wiley and Sons Inc 2010 35 Agostinho Fonseca Apontamentos de ensaios em voo Instituto Superior T cnico Portugal 2011 36 Antenna polarisation http www air stream org au technical references antenna polarisation Accessed 2015 01 05 37 Diamond Antenna A430s10 base station yagi beam January 2007 38 UHF RC system MCX wire antenna detailed datasheet Thomas Scherrer LRS February 2011 39 Joshua Bardwell About 802 11 signal and noise metrics Document D100201 2004 40 H T Friis A note on a simple transmission formula R E and Waves and Electrons 1946 41 Carlos Fernandes Estimar o alcance de uma liga o assumindo desimpedida utilizando a equac de friis Instituto Superior T cnico 2014 42 Firs
99. one in the Config Tool in a few steps presented below Fig 5 5 shows the window where this can be done File Video Mode Options Help CT Tool Status Presented model type Plane w Presented Charset MinimOSD 2 4 0 1 mem Config Panel 1 Panel 2 RSSI channel Mavlink RSSI Ee Speed ema RSS Min Value g RSSI Max Value Overspeed km h 255 40 E RSS Waming Level z Call Sign Is 51 Enable Raw alb2ec2d4 MinimOSD Extra Config Tool 2 4 0 1 Pre Release r 88 EM OSD Status Model Type found in 05D Unknown Last charsel uploaded io OSD Unknown Units Metric a Min Battery Voltage 4 10 1 Bat Remain Wam Level x 10 dg Show remaining Figure 5 5 Configuring the MinimOSD to correctly read the RSSI values In Config Tool check the RSSI Enable Raw check box so that when the OSD is powered up with the APM the raw values are seen and check if the RSSI channel is set to MAVLink RSSI After the APM has booted up and with the RC Tx is working the screen will show the raw value that after has to be set in the RSSI Max Value box With the RC Tx turned off it will then show the raw value that has to be set in RSSI Min Value Plug the OSD to the FTDI cable again and uncheck RSSI Enable Raw check box and change the Max and Min values 230 for Max and 150 for Min 5 1 4 Video Transmitter Setup The video transmitter is connected to the Mini
100. opagation loss 6 different parameters were taken into account 67 e Image colours Image contrast Image borders Movement continuity Flickering Smearing With these evaluation parameters and the different video shots from each checkpoint and each an tenna configuration the video quality was evaluated in terms of colour contrast borders and movement continuity on a 10 point scale from bad to excellent while flickering and smearing were rated also with a 10 point scale but from very annoying to not annoying 6 2 2 Test Results Regarding propagation losses Fig 6 7 illustrates how video quality is affected by the distance between operating antennas according to the subjective opinion data gathered The same figures show that 91 e Flickering and smearing are the ones that most affect the quality of the video and the ones that are most affected by propagation loss the increase in distance e When different polarisation is used from each side the image quality tends to get worst Specially regarding flickering and smearing so it is advisable to use antennas with the same polarisation o _2O __ Smearing jr Smear ne eee a gt RN Mov RE rt Continuity n m mM _ Flickering O Oe Mov Continuity ee ae OO EOE WE Contrast gs Colours Fr Borders Contrast e Colours Fr 0 2 6 8 4 Rate for Quali a Vertical GCS Vertical UAS e
101. or records not only the instantaneous current consumption but also keeps track of battery level recording precisely the energy in mAh consumed Features from the EzOSD can be seen in Table 4 2 MinimOSD RVOSD EZOSD Home Distance V V V Home Direction T Y V Throttle Y T X Speed V J Y Altitude Y T Y Battery Status J J J GPS coordinates NG Y X Pitch row and heading angles v Y Y Flight Modes NG Y X RSSI Y NG X Variometer V V X Artificial Horizon Y T V Table 4 2 Main Features of the OSDs considered the MinimOSD the RVOSD and the EZOSD 47 33 48 Taking these comparisons into account the MinimOSD is a viable choice since with its low price and provides has as many features as the RVOSD has The EZOSD does not seem to provide Euler angles which in case of using a camera gimbal is absolutely necessary so that the pilot has a precise notion of the flight it is taking Also with the flight controller already chosen it is important not to have any compatibility issues and for the fact that it is a very popular item it comes with a growing support 30 platform MinimOSD Extra that is constantly improving it Figure 4 2 MinimOSD from 3DRobotics 47 4 1 3 Video Transmitter and Receiver With the use of analogue cameras digital video systems being in an unaffordable price range the RPV video system has to be an analogue RF system They are fairly inexpensive being mass produced and allow long ranges
102. ot affected by it In Pinpoint 9 shows a video link completely lost as seen in Fig 7 14 f However since the UAV is already in line of sight the antenna was easily readjusted This point shows how relevant an antenna tracker can be 19 7 2 3 Overall Flight Quality Pinpoint 10 marks the landing of the UAV and end of the flight The UAV travelled a total of 8 7 km and it only spent 2425 out of a 3S LiPo battery with 4200 mAh capacity The most limiting factor was not having the 3DR telemetry radio telling the pilot where the UAV was since it has a maximum range of 500 m with the current configuration However the obtained telemetry data retrieved from the OSD showed to be very reliable Combining that with the use of the camera gimbal was enough to guide the pilot successfully The risk of losing the video and or RC links in the middle of a flight is a threatening reality Thus the use of an antenna tracker is something to consider The use of a different antenna directional with higher gain on the 3DR telemetry radio will give more range to the antenna tracker however the radio can only emit at an output power of 100 mW 76 Chapter 8 Final Considerations A solution for Remote person view RPV using commercial off the shelf COTS equipment is presented and analysed For the success of this dissertation mission objectives and RPV requirements are defined and explained Next a RPV design is proposed and evaluated in a con
103. overall video quality in standalone and installed configurations transmission However when the RC Tx was turned off on the last checkpoint the video quality did not improve as it can be seen in Fig 6 14 It stayed with the same smearing and flickering it had before By comparing Figs 6 13 6 14 and 6 15 one can visually check the above mentioned Frequency Planning Regarding frequency planning the evaluation of video quality corresponding to each video frequency was done the same way as in Section 6 2 but in the form of a table at 6000m Ch Freq Ch Nr Colours Contrast Borders Mov Continuity Flickering Smearing AVQ 1080 4 4 4 4 4 4 4 4 1120 5 3 3 3 3 3 3 3 1160 6 5 5 5 5 5 5 5 1200 7 8 8 8 8 8 8 8 1240 8 8 8 8 8 8 8 8 1280 9 8 8 8 8 8 8 8 1320 H 7 7 7 7 7 7 7 Table 6 9 Evaluation of video quality depending solely on the transmission frequency lt can easily be seen from Table 6 9 that from channels 7 to 9 there seems to be not much of a difference and that they are the best channels to be transmitting on it is important to say that channel 8 is the closest from the Scherrer s 3 harmonic thus it can be said that there is no interference However there are other unrecognised noise sources that heavily degrade the system near the 1120 MHz frequency Concluding there was the expectation that the RC ground system would cause interferences in the video ground station but this experiment showed a different kind of interf
104. p Chord m 0 11 Stabiliser Sweep Distance m 0 06 Stabiliser Half Span m 0 3 Distance between Leading Edges m 0 74 Stabiliser Type T tail Static Margin 10 Mean Aerodynamic Chord m 0 22 Sweep Distance at MAC m 0 01 From Root Chord to MAC m 0 44 Wing Area m 0 3944 Stab Area m 0 1 Aspect Ratio 8 96 Tail Volume ratio 0 71 From Wing Root Leading Edge to AC m 0 06 From Wing Root Leading Edge to CG m 0 11 From Wing Root Leading Edge to NP m 0 14 Table B 2 Skywalker data for the calculation of the center of gravity In cruise condition most of the lift force is generated by the wings with ideally only a small amount generated by the fuselage and tail The longitudinal static stability may be analysed by considering the aircraft in equilibrium under wing lift tail force and weight The moment equilibrium condition is called trim and is the aircraft condition of concern For an aircraft to be stable in pitch its center of gravity CG must be forward of the Neutral Point NP by a safety factor called static margin which is a percentage of the mean aerodynamic center MAC Table B 2 provides all the characteristics that allow an estimation With this aircraft data and recurring to 72 it is possible to estimate the position of the ideal center of gravity The mean aerodynamic chord MAC was estimated to be 0 22 m located at 0 44 m from the wing root and the sweep distance at the MAC 0 01 m Thus the aerodynami
105. pC B 9 where Cr is the lift coefficient for maximum lift to drag ratio which is related to the maximum MAT range The value for Cz was obtained empirically from pilots that suggested 75 an estimate of 1 72 which translated in a value for the stall speed of 8 m s and a climb velocity of 10 m s Base Drag Coefficient Cp To calculate the base drag coefficient the whole aircraft was approximated to a wing using turbulent flat plate studies The base drag coefficient is given in 74 as a function of the friction coefficient Cy the Swe form factor F Wet Area Area ratio and the interference factor Q as shown in B 10 Cp C produ B 10 where each parameter is estimated through B 11 B 12 B 13 respectively and Q is approximately 1 for the high wing configuration of the Skywalker Table 4 2 p 75 74 0 455 Or 0 0068 B 11 logioRes 2 58 l where Re is the Reynolds number and where the flow was considered solely turbulent in order to 95 estimate the worst case scenario of drag 0 6 di 2 C mazx t c 100 t c 1 34M 18 cos As ec 28 B 12 where x C mar IS the chord wise location of the maximum thickness point of the airfoil section t c and A the sweep angle of the maximum thickness line 74 Dwet _ 1 977 0 52 S Cmax B 13 where Table B 4 shows the input parameters obtained from actually measuring the airframe and the output parameters that
106. php products_id 1195x0sCsid 7c6b025c8274cec5164f 7099c80b117e October 2013 Accessed 2014 10 13 56 Hobbyking website for model testbed http www hobbyking com Accessed 2014 10 22 57 Q Huynh Thu and M Ghanbari Scope of validity of PSNR in image video quality assessment Electronics Letters 22 13 2012 58 Y A Al Najjar and D Chen Soong Comparison of image quality assessment PSNR HVS SSIM UIQI International Journal of Scientific and Engineering Research 3 8 2012 59 National Instruments Peak signal to noise ratio as an image quality metric National Instruments 2013 60 Z Wang Why is image quality assessment so difficult Acoustics Speech and Signal Processing ICASSP 1V 3313 3316 2002 61 A Watson J Hu and J McGowan Ill Dvq A digital video quality metric based on human vision Journal of Electronic Imaging pages 20 29 2001 62 Telecommunication Standartization Sector of ITU Subjective video quality assessment methods for multimedia applications International Telecommunication Union 2008 63 Ardupilot APM and PX4 Configuration for Plane http plane ardupilot com wiki arduplane setup first time apm setup Accessed 2015 04 1 64 A3DRobotics UAV Technology Apm 2 6 for external magnetometer December 2013 65 Minimosd extra support website https code google com p minimosd extra Accessed 2014 02 19 66 why the skew planar antenna is better than a stan
107. ping Spread Spectrum Global Positioning System Lithium Polymer Line Of Sight Long Range System radio control On Screen Display Pulse Period Modulation Radio Control Remote Person View Received Signal Strength Indicator Receiver Transmitter Ultra High Frequencies Unmanned Air Vehicle Very High Frequencies xxi xxii List of Symbols P P G Gt A R C f Fu Power available at the input of the receiving antenna Output power of the transmitting antenna Gain of the receiving antenna Gain of the transmitting antenna Wavelength Distance between antennas Speed of light Frequency Fade Margin XXIII XXIV Chapter 1 Introduction 1 1 Motivation Unmanned Air Vehicles UAV made their way through the military sector They have evolved con siderably in the last decade due to the fact that they are seen as a low cost and expendable way for highly dangerous secret or politically sensitive missions They are in fact getting a bad reputation but a large number of civil applications are taking advantage of these technological advancements for a greater good Sensor technology data processing hardware and software algorithms have made the UAV a highly feasible approach in fire detection rescue operations precision agriculture maintenance journalism coverage and inspection of critical zones 1 Figure 1 1 UAVs helping farmers 2 As technology improved and considerably dropped in price
108. ple static test to the APM and RC receiver was done because their energy consumption depend on too many variables for example the type of flight operation if it is in manual or automatic control how much use it is given to the servos etc For this test a wattmeter is coupled with the system in each experiment 6 5 2 Test Results Regarding the engine when choosing a battery it is recommended that the current of the battery ex ceeds that of the motor This ensures that even if the motor is running at 100 the battery does not hold it back The motor current is calculated as follows Maximum power of motor 328 W Battery voltage LiPo 3S 11 1 V Maximum motor current 328 11 1 29 55 A A battery pack with current discharge rating above 29 55 A is therefore needed For a three cell LiPo battery pack chosen with the following specifications Battery capacity 4 2 Ah Maximum Discharge current 45 C Battery Maximum discharge current 189 A it is seen that the amperage of the battery well exceeds that of the engine and so it is suitable for the design For each test the components were evaluated through a Wattmeter in Voltage Amperage Wattage and accumulated energy consumption in mAh Table 6 18 shows how each sub system behaved with a 3S LiPo battery with 4200 mAh capacity As it was expected changing antenna does not affect the energy consumption with the exception of the radio control transmission the monopole ante
109. post processing techniques to reduce the costs of traditional noxious weed mapping The study found that the automated post processed photos were not positioned sufficiently accurate to produce consistent and accurate weed perimeters In order to increase the accuracy of the weed maps the project had to rectify the photos and hand digitized the weed perimeter which was time intensive and the associated costs exceeded the traditional on foot method The Virginia Polytechnic Institute and State University integrated MicroPilot technology for precise aero biological sampling above agricultural fields Five different flight patterns were explored to deter mine the most appropriate sampling path for aero biological sampling above crop The project completed 25 sampling flight tests conducted from 10 m to 100 m above agricultural fields The study concluded that an orbital sampling pattern around a single GPS waypoint exhibited high positional accuracy with altitude standard deviations 16 In 2012 Roberto Montiel broke the world record for range in a remote control model glider using a camera onboard Most of the flight was done soaring power off taking advantage of thermal air up drafts The starting point was Algora Spain and the route extended SouthEast 111 km and return to the Start 222 km The total flight time was 6 hours 1 3 Project Framing The present dissertation is part of the project of a long endurance electric unmanned aircraft vehicl
110. present work it is important that the selected autopilot respects the following requirements e Small dimensions and weight e Low price e Waypoint following capabilities 19 e Configurable The physical specifications of the autopilots are particularly important in small UAVs in which space payload and power are very limited Size weight specifications are shown in Table 3 3 The following flight controllers were chosen due to the relative popularity amongst users the APM 2 6 the Pixhawk and the RVOSD the functional specifications are listed in detail in Table 3 4 APM2 6 Pixhawk RVOSD Size mm 67x41x15 5x15 5x81 5 66x40x20 Weight g 33 38 32 Price EUR 240 280 300 DC In V 5 6 4 1 5 7 6 25 CPU MHz 168 168 NA Memory Mb 4 4 NA Table 3 3 Comparison of physical specifications of autopilots 31 32 33 APM2 6 Pixhawk RVOSD Waypoints Navigation Vv Auto take off and landing Y Altitude Hold Y Airspeed Hold Y OSD X Telemetry X ER ORR ae a Table 3 4 Comparison of autopilot functions 31 32 33 Regarding the RVOSD and Telemetry functions its construction means that it is not necessary the acquisition of an On screen display OSD as it is in the case of the other two autopilots since both functions are already embedded in the system The APM was chosen because it is the cheapest one of the three it has been used by many pilots meaning it has proved capabilities and 29 explores its many capabilit
111. r was supposed to arrive with a power supply that goes on the wall which did not come but a more practical solution was approached Having an input voltage range of 5 to 30 V a plug adaptor was made to connect it to a 3S LiPo battery which made the DVR a portable device With this device 1 5 GB Gigabyte will record 1 hour of flight so a 12 GB SD card will record the desired projects flight of 8 hours discussed in Section 1 3 4 2 Propagation Aspects of Video Transmissions Much effort has been made in recent years to develop objective image quality metrics that correlate with perceived quality measurement but only limited success has been achieved Peak Signal to Noise Ratio PSNR coupled with the Mean Square Error MSE is the most used objective image quality metric but they are also widely criticized for not correlating well with perceived quality measurements The MSE for practical purposes allows to compare the true pixel values of the original image to the degraded image lt represents the average of the squares of errors between the actual image and the noisy image and it is proposed that the higher the PSNR the better degraded imaged has been reconstructed to match the original image and better the reconstructive algorithm However the main limitation of this metric is that it relies strictly on numeric comparison and does not actually take into account any level of biological factors of the human vision system 57 58 59 In 60
112. ral design using advanced model building techniques A total of two models is built a first generation prototype and a second generation prototype Flight Testing The full scale prototypes testing includes systems checks on ground wind tunnel tests to assess aerodynamic performance static thrust under varying solar conditions and finally flight tests The first aircraft is operated under radio controlled mode which allows for through checks of the solar powered propulsion system The second aircraft is used to test the overall design refinement and also the autopilot hardware and software As for this dissertation its focus falls into the Communications and Electronics task where its objec tive is to implement both a video and radio control systems capable of responding the long endurance requisites of the project The mission profile for the LAETA project can be summarised as follows 1 Take off at sea level with mass 4 9 kg 2 Climb up to 1000 m altitude 3 Fly for 8 hours in the equinox 21 March or 21 September at an altitude of 1000 m at low speed to be defined by system efficiency but greater than 6 m s and maximum speed of 21 1 m s 4 Descent 5 Landing in the field at sea level 1 4 Objectives The objectives of this thesis are design construct and test a remote person view RPV system in order to control a long endurance electric UAV The expected results include detailed design setup and test of th
113. range capability and de veloping upgradable modular avionics to enable easy software upload and or hardware swap to meet the selected mission requirements For the elaboration of these requirements and specifications of the RPV system a plan was made with the following tasks 1 Conceptual Design At this stage several configurations are evaluated where the goal is to meet or exceed the mission requirements endurance size and cost 2 Propulsion System Secondly several electric propulsion system configurations are considered comparing electric performance weight and cost Solar panels are selected in function of the electric brushless motors 3 Aerodynamic Design Definition of the wing geometry Wing is sized for the propulsion system avionics and auxiliary systems Tail is designed from first considerations of static stability As the design progresses their geometry will most likely have to be revisited 4 Noise Prediction Here the mechanisms associated with wing and airframe noise generation will be addressed Analytical codes will be implemented for the UAV in study that will be taken as input variables for the optimisation study 5 Structural Design and Aeroelastic Analysis The airframe both internal structures and external skins is designed in this task with the goal of achieving a light and strong enough structure while keeping its manufacturing cost reasonable 10 11 Design for Manufact
114. re with one another Another objective of interest is to access the telemetry radio connection range Summarizing this test is divided into two experiments as shown in Figs 6 9 one that tests the range of the telemetry radio and another that tests the interference of both 433MHz system on each other a Range test b Interference with RC system Figure 6 9 Tests of telemetry radio 6 3 1 Testing of the Telemetry Radio range For this test it is used the same route as in Fig 6 3 the same used for testing the communication system The equipment is composed by e Telemetry radios and antennas onboard and ground station e Computer e Ardupilot APM The procedure for this experiment is the following e The APM is connected to the telemetry radio TR and then it is powered through the power module e The ground station TR is connected to the PC through an FTDI cable the corresponding driver has to be installed otherwise the PC will not recognize the COM port e In the main page of the Mission Planner the two radios are connected e The RSSI is appointed in the Flight Data menu in the HUB windows as shown in Fig 6 10 55 e This is done at every checkpoint until the link goes down Figure 6 10 Test of the telemetry radio link system configurations Checkpoint Intensity of Connection 90 deg Inclination Distance km 1 99 97 0 2 97 89 0 36 3 0 0 1 5 between 2 and 3 44 42 0 85 Table 6 6 Lin
115. reases the RSSI decreases as expected The peak of maximum distance retrieves a RSSI of 79 120 2500 RSSI Dist Home 2000 x A 80 k ji ya ee m u 2 ot er au AN ed g 1500 E EA 2 x 1000 40 500 20 1 2 3 Time min Figure 7 11 Overall flight data for a short range flight Comparing this result with the ground tests from Fig 7 3 it can be said that ground effects can greatly influence the link since on the ground at 2 km distance the retrieved RSSI was 60 and in the air the RSSI retrieves 79 In Fig 7 11 there are three marked situations where the RSSI drops below 50 On the first pinpoint 1 it is seen that the RSSI drop is very short This fast rise is explained by the fact that the UAV was still in line of sight and the Yagi was easily reoriented The second fall was already on the way home and the UAV was not in line of sight For this reason the drop lasted thirty seconds When the Yagi and UAV were realigned the RSSI retrieved 79 From the second pinpoint 2 to the third 3 the Yagi is not reoriented However the pilot changes the course of the UAV so that the influence of the directivity can be evaluated for a longer range then in Section 7 1 1 As it can be seen from Fig 7 11 minute 10 is where the directivity is greatly noticed the UAV is 1 km away and 42 rotated from the Yagi orientation in theory 30 would be the limit and the RSSI suddenly drops to 60 The
116. rm of a ramp along which the aircraft is accelerate on a trolley until the aircraft reaches an airspeed at which it can sustain airborne flight On the other hand the recovery equipment is usually a parachute or even a set of wheel that allow the aircraft to land in a run on landing For the particular case of RPV system used in this work it will be hand launched and prepared for belly landing For simplification in this thesis the systems are divided into control that goes airborne and in the ground and video that goes airborne and in the ground 2 2 Legislation 2 2 1 Bandwidth Legislation The authority that regulates radio frequencies in Portugal is ANACOM Autoridade Nacional de Comunicac es There is a document publicly available 19 that defines the bandwidth of frequencies available for ama teur radio control and video transmissions Table 2 3 was built from that data Bandwidth MHz Applications 430 440 Amateurs and Local Radio 1240 1300 Amateurs 1260 1270 Amateurs 2300 2400 Amateurs and Local Radio 5650 5670 Amateurs 5668 5670 Amateurs 5670 5725 Amateurs 5725 5830 Amateurs 5830 5850 Amateurs and Local Radio Table 2 3 Attribution of frequencies by ANACOM Summarizing with the respective license there is the possibility of choosing the frequencies in Table 2 3 for applying in this dissertation This will later be taken into account when selecting the components used for the designed RPV system
117. ronmental restoration at oak ridge national laboratory In Proceedings of the 23rd Annual Association for Unmanned Vehicle Systems International Symposium and Exhibition Innovations for the Future 1996 10 M C Quilter and V J Anderson Low altitude large scale aerial photographs a tool for range and resource managers Rangelands 2000 11 Digital photos from solar airplane to improve coffee harvest http www nasa gov centers ames news releases 2002 02 27AR html Accessed 2014 10 22 12 S T Simpson T Stombaugh L Wells and J Jacob Imaging techniques and applications for uav in agriculture International Journal of Agricultural and Biological Engineering 6 031105 2003 13 PJ Hardin and M W Jackson An unmanned aerial vehicle for rangeland photography Rangeland Ecology and Management 58 4 2005 14 V Espinar and D Wiese An extreme makeover scientists upgrade a toy plane with robotic tech nologies GPS World pages 20 27 2005 81 15 P Clegg L Bruciatelli F Domingos R R Jones M De Donatis and R W Wilson Digital geological mapping with tablet pc and pda A comparison Computers and Geosciences 32 10 1682 1698 2006 16 B R Dingus The use of unmanned aerial vehicles for aerobiological sampling M s thesis Virginia Polytechnic Institute and State University 2007 17 A C Marta and P V Gamboa Long endurance electric UAV for civilian surveillance missions In 29 Congr
118. rovided a safe place to do all the necessary pre flight and flight checks before attempting a new range mark The goal of this test was to evaluate the performance of both the RC and video links while going further and further from the ground control station The whole flight was done in manual mode 7 2 1 RC Link Quality This flight test was performed solely in manual mode since the interaction between the RC Tx and Rx is one of the two subjects of evaluation For safety reasons the Yagi antenna was manually oriented so that the levels of RSSI were as high as possible The farther the UAV was the more difficult it was to orient the Yagi the output power of the TSLRS was always at 500 mW The whole ground station was powered by a car battery since all its equipment works at 12 V and and the battery can be constantly recharging The sense of orientation of the pilot played a major role in this flight The values of RSSI were retrieved in order to evaluate its variations within a maximum range of 2200 m The flight path can be seen in Fig 7 10 re D lt rs 2 Fa I a j s F Ne Y y u ae a t a y e er Y je at gt i AS ml 227674 Ea E E y Ea E Y A x AG s Y E N ne es WSs WES CIS CEC ta A E gt gt a y nn rad Figure 7 10 Flight path of the 2 2 km flight test 2 Regarding the relation between the distance home and the RSSI it is seen from Fig 7 11 that when the distance inc
119. signal drops less than 1 km away and even the helical configuration starts breaking at a distance of 3 km see Table obstruction In conclusion the best configuration for a long range flight is a circular polarisation with high gain antenna at the ground station The circular polarisation will overcome banking and obstructions and the high gain antenna will allow coverage of a farther flight However having a directional antenna will increase the risk of losing link suddenly because of the reduced aperture angle The UAV will have to be flying almost in a straight line for it not to break the link For this problem an antenna tracker would solve the issue since this device tracks the transmitter and points the ground station antenna to where the UAV is As for the obstruction although the circular polarisation seems to correct the issue a diversity device could correct it permanently As said in Subsection 6 1 2 the estimates that were done are very conservative due to the fact that these tests are performed 2 m above the ground When flying at 1000 m altitude better results are expected 54 6 3 Testing of the Telemetry Radio The telemetry radio allows the connection of the ardupilot APM via MAVlink to the computer It allows the user for example to modify the mission while the UAV is still in the air The purpose of this test is to check if the long range RC system LRS and the telemetry radio for working in the same frequency interfe
120. sive As it was said before the video systems used for RPV are mass produced This mass production is doe by many different companies but in a very generic way For example the two analogue receivers from Table 4 4 use that same Comtech module Whereas the quality of the 2 analogue systems is very similar in terms of performance that the Partom weighs 9 g less and with 15 less output power there is a 30 reduction in consumption this leads to the conclusion that the Partom is more energy efficient Also it is less expensive than the Lawmate For these reasons the Partom was selected The complete system is shown in Fig 4 3 1 Onboard transmitter H2 Ground station receiver 3 Standard antennas Figure 4 3 Video system developed by Partom 4 1 4 Video Feed Antennas With the video system and camera already chosen the type of antenna is now narrowed down The working frequency will be 1 2 GHz and since the desire is to have long range the ground station antenna will be a directional and high gain one As for the onboard antenna omnidirectional circularly polarized antennas usually used because for being circularly polarized they naturally reject multipath 32 interference However an omnidirectional antenna is not famous for obstruction capabilities 22 The chosen onboard antenna is a skew planar wheel antenna shown in Fig 4 4 a which weighs 6 g has a 2 dBi Gain and omnidirectional radiation pattern see Fig 4 4
121. ssue one person stood right in front of the helical antenna and the conclusions from Section 6 2 of this fact are once again confirmed Although this is the less affected configuration it can be seen from Fig 7 12 b that obstruction can greatly affect the video link It is noteworthy that the obstruction test was done only 26 m away from the ground station a UAS at 69m b UAS at 140m Figure 7 13 UAV gaining altitude and with the Helical pointed directly towards it 2 On the second pinpoint 2 the helical antenna was oriented towards the UAV and the image became clearer when compared with the one from pin 1 Fig 7 12 a as can be seen in Fig 7 13 b Also at this point the UAV is 100 m higher then in pin 1 which also means the ground effects are less influential on the video quality The third pinpoint 3 is noteworthy because at this point the antenna was readjusted and when comparing Fig 7 14 a with Fig 7 14 b from pinpoint 2 it is clear that an antenna repositioning makes all the difference On the forth pinpoint 4 the pilot has to do a terrain recognition making the soeedway the stadium its reference points as seen in Fig 7 14 b so that the ground station antennas could be reoriented 74 p 38 6240 4 st g 19288 a ag sa Sit 1052 Baum 798 2 vom bersreen 974m GverSpeeo a Effect of reorienting the Helical an b Making use of the camera gi
122. stant rate dV dh 0 where V is velocity and h is altitude the rate of climb becomes 74 dh T D a Vetimo sin y Vetimb 7 B 4 where T stands for thrust D for drag W for weight and y for the climb angle And so the required thrust for climbing can be calculated as T Wsin y D B 5 For subsonic climb the total drag is the sum of the base drag with the drag coefficient Cp and the lift induced drag Therefore 74 D qSCp 4SC nARe B 6 94 where q stands for air dynamic pressure S for platform area AR for Aspect Ratio and e for wing efficiency factor as in 74 assumed 0 8 for simplicity Finally an equation for the required thrust for climb is obtained in Eq B 7 2 te W sin y p5 qS CD ae gr AReS B 7 and also for the required Power in Eq B 8 74 P Telimb Velimb B 8 Table B 3 shows the parameters that as of this moment are known Spec Value Weight N 20 AR 8 96 S m 0 3944 p kg m 1 225 S m 0 3944 y deg 20 Table B 3 Measured specifications from the Skywalker Airframe Thus it is necessary to estimate the climb velocity Veiim and the base drag coefficient Cp Climb Velocity From 74 Verim is the velocity that is appropriate to the climb conditions Velimy Viakeof f can be the representative velocity for the take off climb The velocity required for take off is defined as a function of the stall velocity Vstani 74 w 2 S Vro toy 12 TO s
123. system despite being digital is still affected by the area where it is transmitting in Concluding this segment there seems to be no interference of the video Tx onto the RC receiver The experience stopped due to lack of space It is important to say that the video transmission end before the RC which is desirable as previously stated 6 4 3 Pan and Tilt Testing A ITAL SETUP COMFINTUNHO SMULATON TE 280 Ct El install Firmen tm rei A Wizard r ane Sano LU Angie Limits input Ch ee er mn Si f RCE gt gt Mandatory Hardenre J a 5 PE PS M Es al en HELP DICALETE gt gt Optional Hardware Figure 6 17 Camera gimbal setup Regarding the implementation of the pan and tilt servo mechanism of the video camera it was tested in two ways first if it responded to the assigned channels and secondly if it would automatically stabilise if it would respect a predefined floor After trial and error calibration in Mission Planner s initial setup menu Fig 6 17 the values for maximum and minimum servo limits were found and are shown in Table 6 16 Table 6 17 represents the obtained response to the RC controller where the minimum limit for tilt was raised so that the camera would not touch the canopy Maximum Minimum Pan 2100 1100 Tilt 2100 1600 Table 6 16 Servo limits of the pan and tilt 180 180 Mov Continuity Pan Y Y v Tilt Y Y Y Table 6 17 Performance checks of the pan and tilt After pos
124. t Person View FPV Policy Model Aeronautical Association of Australia August 2012 43 C Ononiwug O J Onojo and N Chukwuchekwa Uav design for security monitoring International Journal of Emerging Technology amp Research 11 2 March 2015 44 B Kang J Kim and H Yang Design of multi standard ntsc pal video encoder Current Applied Physics 4 37 42 2004 45 R Hain C J K ahler and C Tropea Comparison of CCD CMOS and intensified cameras Exper iments in Fluids 42 3 March 2007 doi 10 1007 s00348 006 0247 1 46 Kx 181 camera ccd camera http electronicarc com catalogo product_info php products_id 439 0sCsid a1680012e8e8b24100ce0e9750b3158e Accessed 2014 10 13 47 3DRobotics Video OSD kit December 2013 48 EZOSD Overview amp Operating Instructions Immersion RC April 2009 49 ElectronicaRC Partom 850 mW 1 2 GHz video system datasheet May 2014 50 ElectronicaRC Lawmate 1 2 GHz 1000 mW video system datasheet May 2014 51 ElectronicaRC DJI Lightbridge 2 4 GHz full HD digital video downlink Aug 2014 52 Circular wireless products page http www circular wireless com en products page AC cessed 2014 11 6 53 Circular Wireless Skew planar wheel January 2007 83 54 Circular Wireless Helical modo axial January 2007 55 Fieldview 1010 tft high definition lcd monitor for fov 1366x768 led backlight 10 1 inch http electronicarc com catalogo product_info
125. t are going to be tested six configurations total are then evaluated by varying the output power of the transmitter 0 5 1 and 2 W and by switching the antennas Monopole and Yagi Section 3 5 shows how the RSSI can be used as a measure of the signal since it relates signal strength with distance In this particular test the RSSI is retrieved by the Mission Planner with a PC as shown in Fig 6 2 where it is given as a percentage 0 means there is no signal between the GCS and the UAV and 100 means maximum strength 45 a Output power test using the Monopole b Output power test using the Yagi Figure 6 1 Radio link system configurations In order to test the control system without the Telemetry Radio system the ardupilot APM which interprets the RSSI signal from the Rx has to be connected to the PC via USB port In an actual flight it is not possible to have the PC connected directly and so this value is sent to the OSD that gives the RSSI value overlaid on the flight video Figure 6 2 Mission Planner reading RSSI out The place of choice to perform the experiment was Cascais because it allowed the portable device to travel 8 kilometres without obstacles as seen in Fig 6 3 m Ay da Rep blica Ca Parede o no Ra Rey N a um Berto Ile ities Av gt e Rep bpica Figure 6 3 Poinis along the coast where the Radio control experiment took place This experiment was done a
126. t is to evaluate in the same way as in Section 6 2 the interference of the RC Tx in the video system For this test the equipment used is e Video ground station Rx antenna LCD and DVR e RC transmitter and antenna e Video transmitter The location for this test is the same as seen in Fig 6 6 and only the circularly polarized antenna helical with skew planar configuration will be analysed as shown in Fig 6 11 a a f 0 5 1 2W z a Ground station interference with varying output b Evaluation outlook of the experiment power Figure 6 11 Ground station interferences and outlook For the last checkpoint when the video reception is the weakest the video system will be tested in its eight available frequencies in onder to find what the combination with less interferences is Besides it will be important important to know if the video signal has a shorter range than the RC because the video signal degrades progressively and the RC can simply stop working It will be an extra warning that the UAV is getting out of range Thus in this section different aspects will be tested e Video interferences e Video frequency planning e Range For this test two extra components will be added e MinimOSD e APM 2 5 This way it will be possible to evaluate the signal strength through the RSSI as explained in Subsection 6 1 1 Figure 6 11 b exemplifies the outlook of the evaluation 98 With the same evaluat
127. th different configurations and distances a Antenna pattern null with different configurations and distances Obstruction with different configurations and distances 2004 Link Quality from the telemetry radio which is read on the Mission Planner HUB Influence of the LRS on the telemetry radio 2 2 20 0 00002 eee Principle cause for RC Tx interference with video Rx 2 2 0002 ae XV 9 22 3 6 9 Evaluation of video quality depending solely on the transmission frequency 60 6 10 Obtained GPS latitude with video transmitter off and on 0 4 61 6 11 Obtained GPS longitude with video transmitter off andon 4 61 6 12 Read distance from real UAV position with transmitter offandon 62 6 13 Testing the performance of the servos as done in Section6 1 62 6 14 Testing the performance of the communications system on the Yagi configuration without the video system as in Section 6 l ee 62 6 15 Testing the performance of the communications system on the Yagi configuration while the RSSI is provided by the video link nn 62 6 16 Servo limits of the pan and tilt o e a 63 6 17 Performance checks of the pan and tilt o eee a 63 6 18 Sub systems testing in energy consumption 2 2 22 2 m mn nn 65 7 1 Weather conditions dur
128. the Config Tuning StandardParams menu search for the Receiver RSSI sensing pin RSSI_PIN parameter and set it to the desired port number in this case A1 Figure 5 4 APM reads RSSI from Ch12 to channel A1 When using the MinimOSD as in this case there is the need to setup the APM to communicate with it and there are a few requirements that need to be met in order to be able to use the MinimOSD Extra which is the programme that allows the configuration of the MinimOSD The data stream rates have to be configured correctly and to do so the EEPROM parameters on the MP have to be according to Table 5 3 These parameters are configured through the Full parameters list in the in the Config Tuning tab Parameter Value Description SERIAL_BAUD 57 Telemetry output at 57600 SR1_EXT_STAT 2 Extended status stream rate to ground station SR1_EXTRA1 5 Extra data type 1 stream rate to ground station SR1_EXTRA2 2 Extra data type 2 stream rate to ground station SR1 EXTRAS 3 Extra data type 3 stream rate to ground station SR1 POSITION 2 Position stream rate to ground station SR1 RAW SENS 2 Raw sensor stream rate to GCS SR1_RCCHAN 5 RC Channel stream rate to ground station Table 5 3 EEPROM parameters for the interaction between APM and MinimOSD Although the APM already recognizes the RSSI output the MinimOSD has to be recalibrated via 40 MinimOSD Extra so that on the screen it outputs the correct signal strength in percentage This is d
129. their endpoints Distance Okm 0 6km 2km 3 km 4km 6km 8 km 0 5W Y Y Y Y Y Y Y Yagi 1W Y Y J Y Y Y Y 2W Y Y Y Y Y Y Y Margins Contin Margins Contin Margins Contin Mov Mov Mov Table 6 13 Testing the performance of the servos as done in Section 6 1 Secondly the values of the RSSI were written down for every checkpoint as done in Section6 1 with and without the video system turned on The results in Table 6 14 are the same from Section 6 1 and Table 6 15 has the results obtained for the whole system bundled Yagi Okm 0 35km 1 5km 2km 4km 7km 8km 0 5W 100 97 63 57 51 40 O RSSI 1W 100 99 64 60 55 47 48 ow 100 99 67 62 59 50 51 Table 6 14 Testing the performance of the communications system on the Yagi configuration without the video system as in Section 6 1 Yagi Okm 0 6km 2km 3km 4km 6km 8km 0 5W 97 g5 95 93 92 92 84 RSSI 1W 97 96 96 95 95 95 87 2W 97 97 97 97 97 97 90 Table 6 15 Testing the performance of the communications system on the Yagi configuration while the RSSI is provided by the video link As it can be seen the results retrieved with the whole system are clearly better then the ones retrieved with the RC standalone While the first table at km 8 with 0 5 W has 0 of RSSI using the 62 RC standalone platform since the second at 8 km is still showing a strong signal of 84 This can be due to the change in environment or antenna directivity Opposed to what was said in Section 6 1 the RC
130. to be extremely useful to check during flight 3 2 Flight Controller Flight Controller systems are now widely used in modern aircraft and ships The objective of UAV autopilot systems is to consistently guide UAVs to follow reference paths or navigate through pre set 18 waypoints A powerful UAV autopilot system can guide UAVs in all stages of autonomous flight including take off ascent descent trajectory following and landing An autopilot also needs to communicate with the ground station for control mode switch to receive broadcasts from GPS satellites for position updates and to send out control commands to the servo motors on UAV A UAV autopilot system is a closed loop control system with two fundamental functions state esti mation and control signal generation based on the reference paths and the current states The most common state observer is the Inertial Measurement Unit IMU including gyros accelerometers and magnetic sensors There are also other attitude determination devices available like infra red or vision based ones 28 The sensor readings combined with the GPS information can be passed to a filter to generate the estimates of the current states for later control uses Based on different control strate gies the UAV autopilots can be categorized as proportional integral derivative PID based autopilots fuzzy based autopilots neutral network NN based autopilots etc 29 A typical commercial off the shelf UA
131. trolled environment and also through flight testing The performance of this Unmanned Air Systems UAS is then used to evaluate the choices made and to propose a definite and better solution for long range UAS The platform in question is composed by two main systems the radio control and the video feed that together connect the UAV to the pilot The radio control link between the ground station and the UAV consists primarily of an up link trans mitting command from the pilot to the UAV This transmission of commands is done on a radio frequency of 433 MHz and a permissible output power between 0 5 and 2 W allowing a sufficient bandwidth per channel to encode digital data within the limits of the law to travel long distances The video feed on the other hand makes use of a small video camera and an analogue video system on a radio frequency of 1 2 GHz and a permissible output power of 850 mW in order to fly by means of a live video down link displayed on a portable monitor This video system is also retrieving telemetry data through the flight controller and an on screen display 433 MHz ac 1 2 GHz 433 nu Skew Planar TSLRS Tx Wheel Antenna Rx700 antenna Controlled Flight 0 85 mW IdBi Environment a 1 2 GHz 433 MHz 433 Mhz RC gt 8 km gt 2 km 1 2 GHz A RE EN TSLRS A43S10 Diamond Video 8 km gt 2 km Rx Hellaxial Tx700 Yagi antenna Antenna i 0 5 2 W 13dBi 13dBi a RPV long range configuration b RC long range configuration
132. tup The MinimOSD is a small circuit board that gets telemetry data from the APM flight controller and overlays it on the FPV monitor To connect the MinimOSD to the APM 2 5 a 5 pin splitter cable is used The connections shown in Fig 5 3 are required Mule TX ts HOT connected there is also an Ese in parade APM telem port in urder to wee a GSC mn llanos ly Video Transmitter pira sapene hom bariem ETA 5 51 al Sa IN rs ae our mee 4 Td ah E 3555 ur eno Tasi Sac Figure 5 3 MinimOSD between the APM and Video Transmitter Schematics Regarding the setup of the MinimOSD it is based on two components a processor and a video chip From the digital side the flight controller is providing MAVlink data to the OSD processor allowing it to parsing and packaging Then the video chip overlays the data onto the video stream outputting it to the camera It is possible connect the MinimOSD to the computer and load its firmware For this it is necessary an FTDI cable and download its respective driver so that the computer recognises the FTDI cable Both the FTDI and the OSD have 6 pins so the only thing of concern when connecting the two is just putting the Vcc together 5 V with 5 V To configure the OSD there are a couple of programs that need to be downloaded the MinimOSD Config Tool as well as the binaries that contain the firmware MinimOSD Extra 65 is a developer 39 website that is concerned with extending
133. ture should be explored in a long range mission When considering an UAS that not only can perform long distance flights but also flights of long en durance the pros and cons of using directional antennas have to be measured they allow the UAV to travel long distances but with narrow angles of directivity which limits its applications at long distances To solve this issue a long range antenna tracker has to be implemented 19 80 Bibliography 1 R Austin UAS Design Development and Deployment Wiley Wiltshire United Kingdom 2010 2 B Brown Will drones soon replace architects http architizer com blog will drones soon replace architects June 2014 Accessed 2014 10 13 3 Watch a drone visit college football to give coaches better perspective Techcrunch Website Gregory Ferenstein Accessed 2015 04 1 4 Jos Ant nio Cerejo PSP compra ve culos a reos nao tripulados Jornal O Publico December 2013 5 T Hong Air Quality Plume Characterization and Tracking Using Small Unmanned Aircraft 2011 University of California San Diego 6 Jacopo Pasotti Stillfly the newest weapon in the fight against illegal waste dumping 2012 7 Amy Gahran CNN Fighting fire with data spacecraft drones CNN July 2012 8 Rebecca Boyle Introducing the matternet a network of drones for deliveries in remote locations popsci August 2011 9 J E Nyquist Applications of low cost radio controlled airplanes to envi
134. uate the video quality in different situations In the whole UAS communications the video system is the most sensitive and so the one that most suffers from disturbances For this reason in this section it will addressed the various forms of disturbance in video transmissions Atmospheric Disturbances The atmosphere can either increase the signal strength or weaken it If the signal gets refracted as a re sult of changes in the refractive index occurring especially within the first kilometres above the ground it can travel beyond the line of sight of the pilot However if the changes in the refractive index are very abrupt due to weather conditions the signals can be ducted by the ionosphere and be subject to multipath fading causing the distance over which the signal travels to be decreased Although multipath fading is necessarily accounted for in the design of video and communication sys tems it can still be detected through the video link specially on a rainy day 22 Polarization and propagation Losses Even if considering that the path is free of losses there is still a slow degradation of the signal quality since the power received is diminishing with distance This is called propagation loss A horizontally polarized wave is weakened more rapidly by travelling over the ground than a vertically polarized wave While the polarization of sky waves waves that do not follow a path always near the ground usually vary sometimes q
135. uite rapidly and splits into several components that follow different paths ground waves usually retain the polarization characteristics they had when they left the antenna As a rule a vertical conductor radiates a vertically polarized wave and the same goes for a horizontal one 22 The performance of a receiving antenna is improved if it can be oriented to take advantage of the polarization of the incident wave If possible both vertically and horizontally polarized antennas should be tried This means that if the transmitting antenna is vertically polarized in a vertical position and the receiving antenna is tilted 90 relative the the transmitting antenna then theoretically there will be 35 a total loss by polarization This is called polarization loss When a circuit produces mostly surface wave propagation it is important that the antennas at both ends of the path have the same polarization However vertically polarized antennas provide most effective surface wave coverage A propagated ground wave takes three separate paths to the receiver direct ground reflected and surface wave as shown in Fig 4 7 22 Direct Wave ET a SS Y io Reflected Wave ad y oe ee eee Lo Ground Wave en Figure 4 7 Types of Wave Propagation When both transmitting and receiving antennas are close to the ground the direct and ground reflected paths tend to cancel each other while the intensity of the surface wave diminishes in strength
136. ups and there are four usual types of antenna to be adopted for UAS a The dipole antenna erected vertically is vertically polarised and requires a receiving antenna to be similarly polarised or a significant loss of signal strength will result 1 b The Yagi Uda antenna contains only one active dipole element backed up by a number of passive reflector elements which modify the basic radiation pattern to a predominantly directional beam with however small side lobe radiations 1 c Parabolic dish antenna as the name implies are so formed and as a pure parabola By changing the disc diameter for a given radio frequency beams of various widths may be generated 1 d A square patch will produce an antenna with equal beam width in vertical and horizontal directions whilst beams of different width in the two planes will result from rectangular patches 1 To describe the performance of an antenna three major parameters should be considered 34 Antenna Bandwidth The fact that an antenna is designed for a specific frequency or resonance frequency does not mean it is unable to transmit or receive signals from other frequencies Any antenna has a bandwidth which is the range of frequencies where the antenna is able to operate with acceptable efficiency 35 To determine the bandwidth of an antenna or how well they behave for a given frequency there are different parameters For example the reflection parameter which measures
137. uring manufacturing feasibility and integration study is undertaken in order to ensure the manufacturability of the proposed designs Stability and Control During this task the control surfaces are designed to provide enough stability and control authority to the aircraft Empirical data is used and the results are tuned in wind tunnel testing The data gathered from wind tunnel testing is used to develop the UAV controller Multidisciplinary Design Optimisation At this point all the necessary analysis tools for the propul sion aerodynamics structures and controls are in place As such it is possible to couple all these into a multidisciplinary optimisation framework to refine the aircraft design Communication and Electronics In this task the communications and electronic systems are es tablished There are several goals for this task design and implement the autopilot hardware and software make the aircraft systems capable of flight logging and possibly telemetry to a ground station and install all the sensors and actuators in the airframe Aerothermodynamic analysis is performed with the aim of managing the thermal loads from the internal avionics to guarantee efficient cooling in the expected tight bay Telemetry equipment is installed to monitor the aeroe lasticity behaviour Manufacturing Here the construction of the UAV is accomplished The goal is to build the airframe according to the detailed structu

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