Low Altitude Experiments in Technology

Low Altitude Balloon Experiments in Technology (LABET)Version IVEcpE 492: Dec09-14Engr 467: LABETIV_SP09

Henri BaiSteve BeckertIan MoodieMike Rau

Matthew Nelson, AdvisorJohn Basart, Advisor

December 9, 2009

22As real-world engineering becomes more complex and requires the skills of many disciplines, it is difficult to accurately simulate a design process in the classroom.

Goals of LABET project:Design, build, test, and fly a semi-autonomous robotic balloonIncorporate knowledge and skills of multiple disciplines Provide platform where students from AeroE, MatE, ME, CprE and EE can work together to improve upon a similar productProblem Statement3LABET shall weigh less than 1.5 poundsLABET shall have minimum fly time of 20 minutesLABET shall have yaw controlLABET shall have altitude controlLABET shall have ability to traverse forward and backwardsLABET shall have ability to be controlled wirelesslyLABET shall have ability to land autonomously on a table from 4 meters aboveLABET shall have attachment point for 100g balloonFunctional Requirements4LABET should be aesthetically pleasingLABET design should be innovativeLABET should be easy to controlLABET should be completed with thorough documentation Non-Functional Requirements5Operating EnvironmentUse as a promotional tool by client, SSCLDisplayed during tours or eventsTo be operated in Howe Hall atriumFlown indoors only

6Aircraft HardwareProcessorPIC24FJ64GA004Sensors3-axis Accelerometer2-axis GyroscopeSonarCommunicationRF TransceiverFlight Control2 Ducted Fans4 Servo MotorsPower7.4 Volt Li-Ion Array7

Concept Design8Structural DesignTwo fan designThin member design with cross member supportIncludes two cradle cross members for balloon attachment and supportIncludes two landing pad attachment cross membersTwo fans will be mounted using a bi-axial swivel ring

99Chassis MaterialABS PlasticOptimal strength to weight ratioEasy to cut and manipulateProper flexibility for shock absorption though tough enough to prevent yieldingIPS Corporation acrylic cementSpecifically for ABS plasticUsed to bond joints and laminate 2 ABS layersPlastic and Cement Supplierwww.eplastics.com10Weight ReductionAircraft was over weight budget at initial flightBatteries purchased for LABET IV were larger than what was specified (40 grams more total)Analysis was conducted to determine points of interestDetermined material could be removed from cross members, fan gimbles, and fan mounting arms to reduce weightTotal weight reduction: 65 grams

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12Base StationPurposeCommunicate between base station and aircraftSend aircraft movement commandsReceive aircraft status messagesTechnical DetailImplemented in LABVIEWControl scheme uses XBOX360 ControllerMessages received and sent asynchronouslyMessages are sent through serial port, which is transparently handled by RF for the physical layer

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Base Station FlowchartPoll SerialCheck DataPoll Controller DataSend SerialInterface Bad Packet?Parse PacketYes, discardNoBuild Packet15Message ProtocolMessages have the following format:

Example of Movement Command:HeaderData LengthMessage TypeDataXOR3Variable1Variable1HeaderLengthMessage TypeData0x19 0x28 0x3750x44Translation XDataDataDataXORTranslation YYaw CommandElevationCalculated16Aircraft FirmwareInterruptQueues RF Receive DataTimersPeriodically Send Status MessagePoll SensorsMaintains Fan/Servo PositionsMain Loop ( Control )Unloads RF QueueDetermines Desired MotionControl AlgorithmsSet Fan/Servo Positions1717TimersFan/Servo ControlHighest PriorityToggles GPIO to Create pulse, 1ms to 2msOn-Time Set by Control AlgorithmsPoll SensorsMedium PriorityReads ADC, Reads SPIAdjustable Frequency, 0.5 Hz to 20+ HzStatus MessageLow PrioritySends Aircraft Status Message to Base Station18AircraftFirmware

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Base StationLABETTestingLearn about PIC24FJ64GA004Processor ConfigurationUART, SPI, ADCTimers, InterruptsPWM GenerationComponent Testing (Development Board)Accelerometer SPIGyroscope/Sonar Analog, ADCWireless Transceiver UARTFan/Servo Timers, PWM Generation20TestingRC Aircraft TestingComponent IntegrationPrototype BoardExplorer 16 Development Board (PIC24FJ64GA004)21

Control AlgorithmsCreation of Error Signals22

Control AlgorithmsError Signals -> EOMS -> Fans/Servos23

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Resource Requirements26

* As of Dec 11Special ThanksMatthew Nelson (Client, Advisor)Dr. John Bassart (Client, Advisor)Dr. Gregory Luecke (Controls advice)27Questions?28Styrofoam/wood chassisBent plies to provide landing supportOne large fixed, vertically mounted propeller to provide liftServo attached to rudders for yaw controlControlled by computerIndoor use only

LABET History LABET I29Carbon fiber chassis with plastic tubingTwo fixed, vertically mounted motors Tail prop for yaw controlPitch control using servo and strings attached to balloonControlled by computer using custom programmingIndoor use only

LABET History LABET II30Three vertically mounted motorsEach provide 3 lbs of thrust (almost capable of lifting the device without a balloon)Built out of fiberglass and aluminumMore durable chassisIndoor and outdoor use

LABET History LABET III31Structural DesignTwo fan designThin member design with cross member supportIncludes two cradle cross members for balloon attachment and supportIncludes two landing pad attachment cross membersTwo fans will be mounted using a bi-axial swivel ringWill include electronic hardware mounts

32Other Design Considerations

Two fan design w/propLighter weight than three fan designTube structure, easier to buildHeavier than a thin member designFore and Aft control similar to LABET IIThree fan designMost stable designTube structure, easier to buildMost powerfulUses more powerHeavier33Several designs considered and modeled in SolidWorksTwo-fan, Cradle design chosenBest combination of weight, ease of manufacture and stabilityFull size prototypehas been built

Chassis Design34Fans & MotorsBalloon lifts 90% of weightTwo fans are to provide:Lift for remaining 10%Thrust to ascend

Total Fan Thrust = Aircraft weight*(0.10)

Thrust Per Fan = Total Fan Thrust / 2

With a maximum weight of 680 grams (1.5 lbs), the minimum thrust provided by each fan is approximately 34 grams

35Fans & MotorsThree fans from GWS were evaluatedThe chosen fan is the EDF 55-150Pros:Variable thrust output from 32g to 152gHigher efficiencyLower operating voltage to hoverCons:Twice as heavy as the othersCosts $4 more

36ES50 Nano Servo Motor Servos Employed to Provide Rotational Fan Motion 1 Servo Per Axis of Rotation Per Fan4 Servo Motors

Minimize Servo Weight/Cost; 9 g / 10$9 * (4) = 36 g , 36 g = 5.15% WeightTorque: 1. 2 kg.cm at 4.8 VSpeed: 0.13 sec/60Operated at 5 V SupplyPWM Signal For ControlPIC Directly to Servo

37Sonar Measures Altitude for use During Autonomous Landing

Ultrasonic Range Finder - Maxbotix LV-EZ1 3.3 V, 2 mA42 k Hz with Read Rate 1/50 msDistance: 1 cm 500 cm

Analog Output Employed for System IntegrationOutput 10 mV/inch

TestingFull scale RangeTemperature EffectsOutput Accuracy

Available in SSCL

38Invensense IDG-12153.0 V, 7mADual axisIntegrated low-pass filtersAuto zero functionIntegrated temperature sensor

Rotation Rate = (Output Voltage VREF) / Sensitivity

ImplementationThe Silicone Horizon Breakout BoardOn-board regulatorOn-board opAmp buffersPads for passive componentsRight angle header

Gyroscope39AccelerometerSTMicroelectronics LIS3LV02DL 3.3 V, 0.8mA3-axis, Digital sensorHigh (2g) and low (6g) sensitivity

Output Registers: OUTX_L (LSB) and OUTX_H (MSB)

ImplementationSTEVAL-MKI009V1 evaluation boardTransforms the 16 pin land grid array (LGA) into a dual inline package (DIP)IC bus (CS, SCL, SDA) or the SPI bus (CS, SPC, SDI, SDO)

40Lithium-Polymer3.7 Volt Cells

Requirements7.4 VoltsMax Discharge Rate: ~15 ACapacity: ~2200mAhWeight: