Unmanned Aerial Vehicle 16 Foot Wingspan Flying Wing Christopher Good Test Manager, Senior Software Engineer AAI Corporation, Unmanned Aerial Vehicles.

Unmanned Aerial Vehicle16 Foot Wingspan Flying Wing

Christopher Good Test Manager, Senior Software EngineerAAI Corporation, Unmanned Aerial Vehicles Division Graduate Student, Master of Science, Mechanical Engineering Department of Mechanical Engineering University of Nevada, Las Vegas

Home email: [email protected] Work email: [email protected]

This 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.

Flying Wing UAV

PowerTwin Ducted FansOS .65 VR-DF engine Turbax III fan unit

Control Surfaces Elevons Drag rudders(each wingtip)

Flight Control NetMedia BasicX-24 micro-controllerSensorsAnalog Devices ADXL-202 accelerometerNanotron NA070 tilt sensorsMotorola pressure transducersHall-effect sensors & PIC event counters

Upgraded Flight ControlNewMicros ISOPOD

Prototype & Construction

Full size constructionWing tips (6’ each) plug in to the center section, which holds computers, sensors, engines, fuel, RC gear, batteries.

Half size prototype This 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.

Avionics

NetMedia BasicX-24 ($40)

Infra-red remotereceiver for shortrange (<5 ft) control ($5)

Motorola MPX-4115Apressure sensorfor altitude ($20)0-65k feet

Leads to computer serial RS-232 connector

9 volt power

Motorola MPX 2010G low pressure sensors for airspeed ($10 for three)0-1.3 psi, 0-705 mph

The attitude sensors were supplied for free as test units; Analog Devices supplied the ADXL-202 accelerometers and Nanotron supplied the NA-070 tilt sensors.

ADXL-202 accelerometer

NA-070 tilt sensors

Ground Control Station

CompaqLaptop

SERIAL (2)WIT2410 RFCollinearAntenna

NoteworthyPCMCIA

Video Capture

2.4 GHzDown-converter

CollinearAntenna

Gameportto USB

Converter

USBRC to PCGameportConverter

Gameport

JR Radio

Trainer Signal

Autopilot 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 WIT2410 2.4GHz 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.

Data Acquisition,Display

NanotronNA070

Tilt Sensor

NanotronNA070

Tilt Sensor

MPX4115APressureSensor

MPX2010GPressureSensor

Airspeed

Altitude

Pitch

Roll

DIGITAL (1)

DIGITAL (1)

ANALOG (1)

ANALOG (1)

Data 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.

Antenna

uBlox GPS

SERIAL (1)

BOB-IIVideo Overlay

Camera

VideoTransmitter

Dipole Antenna

SERIAL (1)

BasicX-24

RemoteControlReceiver

(x 16)

AnalogADXL202

Pitch rate

Roll rate

Pitch

Sensors

Piezo gyro

Piezo gyro

AnalogADXL202 Roll

DIGITAL (1)

DIGITAL (1)

DIGITAL (2)

DIGITAL (2)

SerialServo

Controller(SSC)

Data Acquisition,Display, Autopilot

Antenna

SERIAL (1)

BOB-IIVideo Overlay

Camera

VideoTransmitter

Dipole Antenna

SERIAL (1)

Autopilot 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.

BasicX-24

uBlox GPS

RemoteControlReceiver

SafetyMUX

SERIAL (1)

NanotronNA070

Tilt Sensor

NanotronNA070

Tilt Sensor

MPX4115APressureSensor

MPX2010GPressureSensor

Airspeed

Altitude

Pitch

Roll

DIGITAL (1)

DIGITAL (1)

ANALOG (1)

ANALOG (1)

(x 16)

AnalogADXL202

Pitch rate

Roll rate

Pitch

Sensors

Piezo gyro

Piezo gyro

AnalogADXL202 Roll

DIGITAL (1)

DIGITAL (1)

DIGITAL (2)

DIGITAL (2)

Data Acquisition,Display, Autopilot,

Navigation

AnalogADXL202

MPX4115APressureSensor

MPX2010GPressureSensor Airspeed

Altitude

Pitch rate

Roll rate

Pitch

Hall EffectSensor

Hall EffectSensor

Tachometer L/R

Sensors

DIGITAL (1)

DIGITAL (1)

Autopilot 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.

ISOPOD

Antenna

SERIAL (1)

BOB-IIVideo Overlay

Camera

VideoTransmitter

DipoleAntenna

uBlox GPS

RemoteControlReceiver

SafetyMUX

Piezo gyro

Piezo gyro

MPX2010GPressureSensor

MPX2010GPressureSensor

Beta

AlphaANALOG (1)

WIT2410 RFDipole

Antenna

SERIAL(2)

SERIAL (1)

DIGITAL (1)

DIGITAL (1)

DIGITAL (2)

ANALOG (1)

ANALOG (1)

ANALOG (1)

(x 16)

AnalogADXL202 Roll

DIGITAL (2)

Sensors

Altitude: Motorola MPX 4115A, ~1 – 15 psi, 0-65k feetVout to measure 0-4000 feet10 bit ADC -> 4 ft resolution12 bit ADC -> 1 ft resolution

(x 16)

(x 16)Non-inverting AmplifierGain = 16 = 1+(RB/RA) = 1 + (1.5M/100K) =

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.

Accelerometers: Analog Devices ADXL202, 2 axix, 2-g accelerometers.

Tilt Sensors: Nanotron NA-070 electrolytic tilt sensors, 0 –70 degree range.

Airspeed Sensors & Pitot Tube Mathematics

I 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)

r(air) @ sea level, incompressible (low Mach number) = 1.229 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 = 1536.25 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) = .4535 kg 1 pound(force) = 32.174 pound(mass) ft/sec2 (multiplied by gravity at sea level)1 ft = .3048 meter 1 ft2 = 144 in2

After 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 = .22 psi @ 111 mph

So, 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.

Airspeed: Motorola MPX 2010G, 0-1.3 psi, 0-705 mph10 bit ADC -> 705/1024 = .68 mph12 bit ADC -> 705/4096 = .17 mph

Video Downlink

Video DownlinkA 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-10 2.4 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.

LL99 99 99 99 99 rr pp mm AA99 99 99 mmpp hh RR 99 99 99 99 99 rr ppmm

PP77 00 UU RR77 00 RR 99 99 99 99 99 ff tt PP 99 00 UU RR 99 00 RR

hh hh :: mmmm:: ss ss GG99 99 99 mmpp hh dd dd :: mmmm :: ss ss NN

HHDD33 66 00 dd ee gg 99 99 99 99 99 ff tt dd dd dd :: mmmm :: ss ss EE

hh:mm:ss = GPS Time G XXX mph = GPS ground speed (mph) dd:mm:ss N/S = GPS latitude HD XXX deg = GPS heading (deg) XXXXX ft = GPS altitude (ft) ddd:mm:ss E/W = GPS longitude

L XXXXX RPM = left tach (rpm)

A XXX mph = air data airspeed (mph) XXXXX ft = air data altitude (ft)

R XXXXX RPM = right tach (rpm)

(Nanotron tilt sensors)P XX U/D = pitch in deg, up/down

R XX R/L =roll in deg, right/left

(Analog accelerometers)P XX U/D = pitch in deg, up/down

R XX R/L =roll in deg, right/left

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.

BOB-II Video Overlay

Servo Control

Serial Servo Controller (SSC)A Scott Edwards Electronics SSC ($29) accepts commands via a serial line and can control up to 8 servos.

GPS

Trimble-Lassen SK8 uBlox PS1

GPS 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.

Trimble-Lassen LP

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 AM50-00002 for $4 from MHz Marketing.

M/A-COMAM50-000021.575 Ghz LNA

TOKO DAX1575MS63TGPS CERAMIC PATCH ELEMENT

Controller PrototypesAmpro 286 miniboard. This single board computer ($40) with a 286 10MHz 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 25+. 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.

Antenna Trimble LP

Antenna

Antenna

MUX

Multiple 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.

Trimble LP

Trimble SK8

Additional Development

Test Hardware

Analog-to-digital converter AD7812. 10 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 ADC0838. 8 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.

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.

The 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.

Test Hardware

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.

Rate 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.