1Unmanned Aerial Vehicle 16 Foot Wingspan Flying Wing Christopher Good Test Manager, Senior Software Engineer AAI Corporation, Unmanned Aerial Vehicles Division Graduate Student, Master of Science, Mechanical Engineering Department of Mechanical Engineering University of Nevada, Las VegasHome WorkThis Master's Project is an on-board autopilot program running on a micro-controller that will control a dynamic system; an aircraft in flight. The aircraft is a 16 foot wingspan flying wing modeled on the Northrop N-9M flying wing. Three aircraft have been built: an 11 foot testbed, a proof of concept half scale 8 foot aircraft, and the full size 16 foot wingspan aircraft with the computer on-board. The onboard computer has an autopilot program. Initially, telemetry will be downlinked within a video signal as textual overlays on the picture. Further development with other controllers will allow waypoint navigation based on GPS input.
3Prototype & Construction Half size prototypeThis plane was built and test flown to prove the airfoil and airframe were stable. An OS 46 engine and tractor propeller provide power. No drag rudders are on this airframe and it is controlled only by remote control.Full size constructionWing tips (6’ each) plug in to the center section, which holds computers, sensors, engines, fuel, RC gear, batteries.
4AvionicsThe attitude sensors were supplied for free as test units; Analog Devices supplied the ADXL-202 accelerometers and Nanotron supplied the NA-070 tilt sensors.NA-070 tiltsensorsLeads to computerserial RS-232 connectorNetMedia BasicX-24 ($40)MotorolaMPX-4115Apressure sensorfor altitude ($20)0-65k feetADXL-202 accelerometerMotorola MPX 2010G low pressure sensors for airspeed ($10 for three)0-1.3 psi, mphInfra-red remotereceiver for shortrange (<5 ft) control ($5)9 volt power
5Ground Control Station JR RadioCompaqLaptopCollinearAntennaWIT2410 RFSERIAL (2)Trainer Signal2.4 GHzDown-converterNoteworthyPCMCIAVideo CaptureCollinearAntennaGameportto USBConverterRC to PCGameportConverterUSBGameportAutopilot and Navigation Flight with RC BackupGround control of the ISOPOD will be done via a WIT2410 RF modem transceiver identical to the airborne unit. The video signal will be down-converted to a base-band composite signal and captured for display on the laptop by the PCMCIA video capture card. This eliminates the need for a separate TV to view airborne video.Manual control of the aircraft will be done with a JR radio. The analog stick movements are converted to the standard JR digital trainer box signal. This digital signal is converted to the standard PC analog gameport signals, and finally converted to a USB signal for input to the laptop.RF Modem DatalinkThe datalink will done with Cirronet WIT GHz spread spectrum wireless industrial transceivers. These plug into the serial ports of the computers at each end of the link and are invisible to the serial connection. They transmit at 100mW and frequency hop to any one of 64 preprogrammed patterns.
6BasicX-24 BasicX-24 Sensors Roll Pitch Roll rate Pitch rate Roll Pitch AnalogADXL202RollAnalogADXL202PitchRemoteControlReceiverPiezo gyroRoll rateDIGITAL (2)DIGITAL (2)Piezo gyroPitch rateDipoleAntennaDIGITAL (1)AntennaData Acquisition,DisplayDIGITAL (1)NanotronNA070Tilt SensorRollVideoTransmitterDIGITAL (1)uBloxGPSSERIAL (1)BasicX-24DIGITAL (1)NanotronNA070Tilt SensorPitchBOB-IIVideo OverlaySERIAL (1)ANALOG (1)MPX2010GPressureSensorCameraANALOG (1)Airspeed(x 16)MPX4115APressureSensorAltitudeData Gathering Flight with RC Control OnlyInitial testing will include data acquisition only; data will be displayed to the controlling PC on the ground and via the BOB-II video overlay module in the air.GPS data is displayed only. Analog input is converted with an 8 channel, 10 bit ADC.
7BasicX-24 BasicX-24 Sensors Roll Pitch Roll rate Pitch rate Roll Pitch AnalogADXL202RollSerialServoController(SSC)AnalogADXL202PitchRemoteControlReceiverSafetyMUXPiezo gyroRoll rateDIGITAL (2)SERIAL (1)DIGITAL (2)Piezo gyroPitch rateDipoleAntennaDIGITAL (1)AntennaData Acquisition,Display, AutopilotDIGITAL (1)NanotronNA070Tilt SensorRollVideoTransmitterDIGITAL (1)uBloxGPSSERIAL (1)BasicX-24DIGITAL (1)NanotronNA070Tilt SensorPitchBOB-IIVideo OverlaySERIAL (1)ANALOG (1)MPX2010GPressureSensorCameraANALOG (1)Airspeed(x 16)MPX4115APressureSensorAltitudeAutopilot Flight with RC BackupAfter data acquisition flights, autopilot control will be added. This is inner loop control: straight and level flight at a preset airspeed. GPS data is displayed only. The SSC, safety MUX, and autopilot inner loop software are added here.
8ISOPOD ISOPOD Sensors Roll Pitch Roll rate Pitch rate Alpha Beta AnalogADXL202RollAnalogADXL202PitchPiezo gyroRemoteControlReceiverSafetyMUXRoll rateDIGITAL (2)Piezo gyroDIGITAL (2)Pitch rateDIGITAL (1)MPX2010GPressureSensorDipoleAntennaAlphaAntennaData Acquisition,Display, Autopilot,NavigationDIGITAL (1)ANALOG (1)VideoTransmitteruBloxGPSMPX2010GPressureSensorSERIAL (1)ANALOG (1)BetaISOPODBOB-IIVideo OverlayANALOG (1)SERIAL (1)MPX2010GPressureSensorANALOG (1)AirspeedSERIAL(2)CameraDIGITAL (1)WIT2410 RFDipoleAntenna(x 16)MPX4115APressureSensorDIGITAL (1)AltitudeAutopilot and Navigation Flight with RC BackupThe ISOPOD has much greater capabilities than the BasicX-24. It has dedicated PWM servo outputs and I/O counters, and will be able to handle all navigation tasks by itself. Analog input is converted with an 8 channel, 12 bit ADC.Hall EffectSensorTachometerL/RHall EffectSensor
9SensorsAccelerometers: Analog Devices ADXL202, 2 axix, 2-g accelerometers.Rate Gyros: Murata Piezo rate gyroscope. I bought a non-working Gyropoint mouse on eBay, cheap. By gutting the mouse and removing the piezo gyro daughterboard, I have two rate gyros already soldered onto a board and ready to use.Tilt Sensors: Nanotron NA-070 electrolytic tilt sensors, 0 –70 degree range.Altitude: Motorola MPX 4115A, ~1 – 15 psi, 0-65k feetVout to measure feet10 bit ADC -> 4 ft resolution12 bit ADC -> 1 ft resolution(x 16)Non-inverting AmplifierGain = 16 = 1+(RB/RA) = 1 + (1.5M/100K)=(x 16)
10Airspeed Sensors & Pitot Tube Mathematics Airspeed: Motorola MPX 2010G, psi, mph10 bit ADC -> 705/1024 = .68 mph12 bit ADC -> 705/4096 = .17 mphI needed to determine what the maximum pressure the pressure transducer would experience in flight, so I could buy the right sensor for airspeed sensing. The pressure in the ram section of a pitot tube is comprised of two components, the dynamic and the static. Because most pressure transducers sense the difference between some input and static (gauge pressure), we only need to look at the dynamic pressure exerted by the moving air.Dynamic fluid pressure is defined as: P(dynamic) = 0.5 (r) (v2) , where v = velocity of fluid (air), r = density of fluid (air)sea level, incompressible (low Mach number) = kg/(m3)We will assume a max velocity of 50 m/s (111 mph). So we get: Pmax=.5 (1.229 kg/(m3)) (50 m/s)2 = kg/(m s2)We need to convert this to PSI. To do that, we need to convert kg to pounds(force), which is different from pounds(mass). Remember the Mars Observer satellite? It went splat because NASA forgot to convert pounds(force) to pounds(mass).1 pound(mass) = kg 1 pound(force) = pound(mass) ft/sec2 (multiplied by gravity at sea level)1 ft = meter 1 ft2 = 144 in2After all these numbers are put in the equation, we get:P(dynamic, air) = 32 pound(force) / ft2 @ 111 mph = .22 pound(force) / in2 @ 111 mph = mphSo, to measure airspeed up to 111 mph, we need a pressure transducer that can read at least .22 psi. I have three Motorola MPX2010G pressure transducers that are rated at 1.4 psi. They should work up to 318 m/s or 705 mph (in an incompressible flow, which at 705 mph is not true, but anyway...) No problem.
11Video Downlink Video Downlink A Pixera mini camera ($26) will take video. It feeds into a Decade Engineering BOB-II video overlay module ($85) that accepts commands via a serial line. The output of that feeds into a Comtech 100mW 2.4Ghz PLL controlled RF module ($45). The RF module is controlled by a PIC ($12) that selects the frequency based on dip-switch settings. The RF module feeds directly into a dipole antenna, built from plans found on the internet.A commercial X GHz receiver ($25) will be used to down-convert the video signal for display on a standard television. I will use a omnidirectional collinear vertical stacked dipole antenna built from plans found on the internet.
12BOB-II Video Overlay L 9 r p m A h R P 7 U f t : s G d N H D 3 6 e g E Bob-II overlays 28 columns x 11 rows of white text with a black border. Everything underlined is updated; all else is static. Air sensor data and attitude data are updated as fast as the micro-controller can process the sensor inputs. GPS data and tachometers are updated at 1 Hz.A XXX mph = air data airspeed (mph)XXXXX ft = air data altitude (ft)L XXXXX RPM =left tach (rpm)R XXXXX RPM =right tach (rpm)L9rpmAhRP7Uft:sGdNHD36egE(Analog accelerometers)P XX U/D =pitch in deg, up/downR XX R/L =roll in deg, right/left(Nanotron tilt sensors)P XX U/D =pitch in deg, up/downR XX R/L =roll in deg, right/lefthh:mm:ss = GPS Time G XXX mph = GPS ground speed (mph) dd:mm:ss N/S = GPS latitudeHD XXX deg = GPS heading (deg) XXXXX ft = GPS altitude (ft) ddd:mm:ss E/W = GPS longitude
13Servo Control Serial Servo Controller (SSC) A Scott Edwards Electronics SSC ($29) accepts commands via a serial line and can control up to 8 servos.
14GPS CERAMIC PATCH ELEMENT Trimble-Lassen SK8Trimble-Lassen LPuBlox PS1GPS ReceiversThe Trimble SK8 (5.0 volts power, $35) and LP (3.3 volts power, $25) each monitor 8 satellites. The LP is a low power version of the SK8, and both receivers output NMEA or TSIP messages on serial port 1. The uBlox ($80) monitors 12 channels, and outputs NMEA or SIRF messages on serial port 1. All receivers accept RTCM-SC104 differential GPS corrections on serial port 2.GPS AntennasI decided to make my own active antenna using commercial components. The TOKO DAX1575MS63T ceramic patch element (18mm x 18mm) is $5 from AVNET. All of these receivers require an active antenna, which means this needs some type of low noise amplifier (LNA). After searching many homemade GPS antenna web pages, I found the M/A-COM AM for $4 from MHz Marketing.M/A-COMAM1.575 Ghz LNATOKO DAX1575MS63TGPS CERAMIC PATCH ELEMENT
15Controller Prototypes Ampro 286 miniboard. This single board computer ($40) with a MHz processor was the first board I picked to be the autopilot on-board computer. It has a small ISA backplane that can be attached for ground testing. More research has lead to the use of the smaller, lighter Flashlite V25+ single board computer.Flashlite V This single board computer ($40) with a 10MHz processor was the next board I picked to be the autopilot on-board computer. It runs a straight DOS 3.3 environment, has a 128KB flash hard drive, and lots of I/O. Continuous advances in hardware have left this board behind also, allowing the much smaller BasicX-24 and ISOPOD to be used.Additional DevelopmentAntennaTrimble LPMultiple GPS ReceiversFurther development may include multiple GPS receivers. All the Trimble units will be MUXed to a single serial port and replace the uBlox GPS.AntennaTrimble LPMUXAntennaTrimble SK8
16Test HardwareThe following pages show some miscellaneous hardware, and some equipment that I built for testing and other hardware configurations. For example, the ADC’s were going to be used for analog input before I decided on using the BasicX-24, which has its own 10 bit, 8 channel ADC.Analog Devices ADXL105’s. Each one measures 1 to 5 g’s in one axis. The small board on top is an op-amp acting as a data buffer.Analog-to-digital converter AD bit, 8 channels. I made this board with capacitors to smooth out the supply voltage (also the reference voltage), and a 7805 voltage regulator as the power supply.Analog-to-digital converter ADC bit, 8 channels. I added two micro potentiometers to channels 1 and 2 for testing. This board also has a 7805 voltage regulator as the power supply.
17Test HardwareRate Gyroscope. A Futaba G153BB rate gyro will be used to smooth out yaw oscillations via the drag rudders. I have an identical gyro in my RC helicopter and it works very nicely.Mercury Tilt Switches. Initial testing was done with a set of mercury tilt switches for absolute left/right roll, up/down pitch. It was built as a temporary input device for attitude input. This will not be used in the aircraft. They were acquired from a air-conditioning company (from old thermostats) for free.Printer Port Indicator. To verify the printer port interactions, I built this indicator device to show when the individual bits in the parallel port I/O area are on and off. The 5 push-button switches are used to manually simulate the data coming from an input device (A/D converter, for example). This was built from parts from Radio Shack and has been used for testing digital I/O with a PC’s parallel port.