BUZZSAT

CONTROL SYSTEM

BUZZSAT

CONTROL SYSTEMRECIEVING SIGNAL TO TRANSMITEARTH NOT SEENSEE EARTHTRANSMIT BEACON

Control System Electronics(CSE)

Digital Inputfrom ReceiverTransmitter

Power Microcontroller

Transmitter

ReceiverPower

ControlSystemPower

Attitude Control System (ACS)

ElectromagneticTorque System

4

Earth Tracker

Controlled PowerACS

Power

Control System ArchitectureControl System Architecture

Hardware Needs

18F452

CM8870 DTMFDecoder

MAX232 LineLev el Conv erter

5

2

IRDetector

Low PassFilter

Network7 IR Detector

MOSFET PowerSwitches

2

• 18F452 Main Controller

• CM8870 DTMF Decoder

• UART in PIC, MAX232 Serial Port Line Level Converter

•MOSFET Power Switches

• Amplifier for IR Detector Voltage feed into 7 kHz Low Pass Filter

Printed Circuit Board

IR Detectors

MOSFET Switches

Serial Port

IR Sensor Low Pass Filters

DTMF Decoder

PIC18F452

Normal Software Tasks

• Starts up and initializes all the necessary hardware inside the PIC…

•ADC for IR Sensors

•PORT I/O for DTMF Decoder

•DTMF Interrupt

Power Up

INIT

LOOPREAD_DTMF

-Print Debug to Serial Port

Decoded DTMFValue

Toggle Transmitter

ToggleMagnetouquer 2

1

• Controller waits in LOOP mode until DTMF Decoder generates interrupt

•Reads received value

•Toggles respective power line

•Prints action to the serial port

• LOOP would be changed to SLEEP in flight mode for power saving.

Hardware & Software Improvement

• Hardware

•Watchdog/Reset Circuit

•Power Switch for each IC

•Power Multiplexer for IR Detectors

•Telemetry

• Software

•SLEEP Mode

•Algorithm for IR Detector Monitoring and Magnet Use

•Telemetry

Orbit DeterminationOrbit Determination

Best Altitude For SatelliteBest Altitude For Satellite Easiest And Cheapest Easiest And Cheapest

Access Of Space Is Within Access Of Space Is Within 450 Km above Earth (Low 450 Km above Earth (Low Earth Orbit or LEO)Earth Orbit or LEO)

Determination of OrbitDetermination of Orbit 45 Degrees Inclination45 Degrees Inclination Passes Over Atlanta In Passes Over Atlanta In

Order To Receive Signal Order To Receive Signal From SatelliteFrom Satellite

Magnetic Field Magnetic Field Measurement In OrbitMeasurement In Orbit

Magnetic Field Effect On EarthMagnetic Field Effect On EarthVaries Accordingly To Four FactorsVaries Accordingly To Four Factors

Altitude Altitude LongitudeLongitude Latitude Latitude TimeTime

Why Is It Important?Why Is It Important? Helps Determine The Effect Of the Satellite Guidance System In Respect To The Torque Helps Determine The Effect Of the Satellite Guidance System In Respect To The Torque

Created By The Magnetic FieldCreated By The Magnetic Field

Determination Of The Orbit Determination Of The Orbit TrajectoryTrajectory

By using a crude method of plotting the orbit, it is possible to By using a crude method of plotting the orbit, it is possible to determine where the satellite will travel across the earthdetermine where the satellite will travel across the earthFrom this information obtained, valuable data can be gathered such From this information obtained, valuable data can be gathered such as the magnetic field effect in retrospect to the location of the as the magnetic field effect in retrospect to the location of the satellitesatellite

Final Orbit Trajectory With Final Orbit Trajectory With Magnetic Field Magnetic Field

Magnetic Field ChartMagnetic Field Chart

Torque CalculationTorque Calculation

With some formulas With some formulas to obtain torque from to obtain torque from magnetic field we can magnetic field we can get the overall get the overall estimation of the estimation of the torque exerted on the torque exerted on the satellitesatellite

earthearth uBuB

BRniAu32

Attitude Control SystemAttitude Control System Function:Function:

Controls satelliteControls satellitei.i. MotionMotionii.ii. orientationorientation

Why control orientation?Why control orientation? To get a better signal from To get a better signal from

antennasantennas Motions causing de-Motions causing de-

orientation:orientation: SpinSpin RotationRotation ProcessionProcession

Attitude Control SystemAttitude Control System

Different ACSsDifferent ACSs 3-axis stabilization (Roll, Pitch, and Yaw)3-axis stabilization (Roll, Pitch, and Yaw) Permanent magnet (Easiest)Permanent magnet (Easiest) Electromagnet (Best Combination)Electromagnet (Best Combination)

Why electromagnet?Why electromagnet? Simple designSimple design Low costLow cost Better controlled fieldBetter controlled field No flipping over polesNo flipping over poles

Attitude Control SystemAttitude Control System

DesignDesign 800 turns 32 AWG enamel coated 800 turns 32 AWG enamel coated

wirewire 10.5 in diameter, 2.5 in width10.5 in diameter, 2.5 in width 500 ohm resistance, 30 mA 500 ohm resistance, 30 mA

currentcurrent 15V supplied from solar panels15V supplied from solar panels Plastic insulation from satellite Plastic insulation from satellite

bodybody Current is switched on and off Current is switched on and off

through Power MOSFET’sthrough Power MOSFET’s Mounted to satellite by metal Mounted to satellite by metal

brackets brackets

Attitude Control SystemAttitude Control System

Torque calculationsTorque calculations Magnetic field for 800 rings of wireMagnetic field for 800 rings of wire

Magnetic dipole moment of coilMagnetic dipole moment of coil

Torque of earth’s field on satelliteTorque of earth’s field on satellite

Time calculations – 90Time calculations – 900 0 (( π/2 π/2) deviation) deviation Satellite’s estimated moment of inertiaSatellite’s estimated moment of inertia

Rotational accelerationRotational acceleration

Time for re-positioning Time for re-positioning

M=satellite mass, n=# of wire loops, M=satellite mass, n=# of wire loops, μμoo=permeability, R=coil radius, i=current =permeability, R=coil radius, i=current through wire, A=area inside coilthrough wire, A=area inside coil

R

iB

2

800

BRniAu32

earthearth uBuB

2

2MRI I

t

Attitude Control SystemAttitude Control System

st 38min

Results

Coil exhibits slow movement and large oscillation about field axis

st 81max

IR SensorsIR Sensors

IntroductionIntroduction

FunctionalityFunctionality

Selection ProcessSelection Process

Testing ProcedureTesting Procedure

IntegrationIntegration

IR Sensors--IntroductionIR Sensors--Introduction

Taking into account the Inverse Square Law, at 400km from Taking into account the Inverse Square Law, at 400km from earth, IR sensors will distinguish the sun from the earth using earth, IR sensors will distinguish the sun from the earth using their different wavelength region of maximum intensity. their different wavelength region of maximum intensity.

Spectrum of the earth. The earth emits most of its radiation in a wavelength band between 0.5 and 30.0 micrometers (µm).

Spectrum of the sun. The sun emits most of its radiation in a wavelength band between 0.1 and 4.0 micrometers (µm).

IR Sensors--Functionality & IR Sensors--Functionality & DesignDesign

Using IR sensors that will check Using IR sensors that will check for radiation at ~10 micron, the for radiation at ~10 micron, the electromagnetic torquing device electromagnetic torquing device will rotate the satellite…will rotate the satellite…

IR

IR

IR

IR

IR

IRIR

IR (6371+400) km

6371 km

6371 km

55°

IR Sensors--FunctionalityIR Sensors--Functionality

……so that the transmission link will be pointed so that the transmission link will be pointed towards earth. towards earth. R

RR

R

RR

IR Sensors--Selection ProcessIR Sensors--Selection Process

MgCdTe (Rad-hard)

Pyroelectric

Thermopile

Wavelength (~10 m)

Price Availability Application

XX

X

IR Sensors--Testing procedureIR Sensors--Testing procedure

General hot/coldGeneral hot/cold Soldering iron Soldering iron ( 0.19 mV ~ 3.30 mV )( 0.19 mV ~ 3.30 mV ) Cold aluminum canCold aluminum can ( 0.07 mV )( 0.07 mV )

Ambient environmentAmbient environment Sky Sky ( 0.094 mV ~ 0.289 mV)( 0.094 mV ~ 0.289 mV) Ground Ground ( 0.135 mV ~ 0.161 ( 0.135 mV ~ 0.161

mV)mV)

Extreme temperatureExtreme temperature Propane TorchPropane Torch ( 3.137 mV)( 3.137 mV) Freezer at -80 Freezer at -80 C C ( 0.005 mV ( 0.005 mV 0 mV) 0 mV)

IR Sensors--IntegrationIR Sensors--Integration

An 351 op-amp will be used to magnify the voltage output of the IR detector

-+

-

1.2M

+

-1.2k

GND

5V DC

OUT

Connectors

System IntegrationSystem Integration

The magnetic coil and transmitter switch The magnetic coil and transmitter switch work very well on the Control Board. work very well on the Control Board.

Integration with the receiver board worked Integration with the receiver board worked well with the proto-board, but we are still well with the proto-board, but we are still waiting for a full integration test with them.waiting for a full integration test with them.

Earth Tracking System works, but full Earth Tracking System works, but full integration into the spacecraft will have to integration into the spacecraft will have to wait for future semester. wait for future semester.

Future Plans and Options for Future Plans and Options for BuzzsatBuzzsat

Calibrate and fully test IR sensors and connection to ADC system.Calibrate and fully test IR sensors and connection to ADC system.

θθφφ

Add new polar coordinate axis of rotation for pointing Add new polar coordinate axis of rotation for pointing the transmitter.the transmitter. θ θ instead of just instead of just φφ. Would be . Would be beneficial to add AE to project for this more complex beneficial to add AE to project for this more complex mechanical control system (momentum wheel)mechanical control system (momentum wheel)

Use MilSpec/RadHard parts and shielding techniques to space qualify the satellite.Use MilSpec/RadHard parts and shielding techniques to space qualify the satellite.Add GPS system for selective transmitting (i.e. only transmit over North America)Add GPS system for selective transmitting (i.e. only transmit over North America)

Budgetary BreakdownBudgetary BreakdownITEMITEM REAL COSTREAL COST COST TO PROJECTCOST TO PROJECT

PIC PIC μμCC $8.50$8.50 SampledSampled

UTMC UTMC μμCC $2500 (2 units)$2500 (2 units) Donation (2 units)Donation (2 units)

Northrop Grumman EEPROMNorthrop Grumman EEPROM $3000$3000 DonationDonation

Perkin Elmer ThermopilePerkin Elmer Thermopile $15 (10 units)$15 (10 units) $180 (10 units + shipping)$180 (10 units + shipping)

Magnetic TorquerMagnetic Torquer $65$65 $65$65

Printed Circuit BoardPrinted Circuit Board $180$180 $180$180

μμC/EEPROM ProgrammerC/EEPROM Programmer $100$100 $100$100

Instrumentation AmpsInstrumentation Amps $50$50 $50$50

Various other componentsVarious other components $50$50 SampledSampled

TotalsTotals $8,603.50 $8,603.50 $585$585

Control System SponsorsControl System Sponsors

Rad Hard EEPROM Valued at over $2200

$500 Check for various costs incurred

Professional Support from Radiation Expert

2 Rad Hard Microcontrollers Valued

at over $5000

IR Sensor Sampling $150 worth