drexel rocksat
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Drexel RockSAT Individual Subsystem Testing Report
Kelly Collett • Christopher Elko • Danielle JacobsonFebruary 12, 2012
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ISTR Presentation Contents• Section 1: Mission Overview
• Mission Statement• Mission Objectives• Expected Results• Functional Block Diagrams
• Section 2: Changes and Updates Since CDR• System Modifications• Project Management & Team Updates• Schedule Updates
3
ISTR Presentation Contents• Section 3: Subsystem Test Reports
• Subsystems Overview• Structural System (STR)• Piezoelectric Actuator System (PEA)• Electrical Power System (EPS)• Visual Verification System (VVS)
• Section 4: Conclusions• Plans for Integration• Lessons Learned
Mission OverviewDrexel RockSat Team 2011-2012
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Mission Statement
Develop and test a system that will use piezoelectric materials to convert
mechanical vibrational energy into electrical energy to trickle charge on-board power
systems.
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Mission Overview• Demonstrate feasibility of power generation
via piezoelectric effect under Terrier-Orion flight conditions
• Determine optimal piezoelectric material for energy conversion in this application
• Classify relationships between orientation of piezoelectric actuators and output voltage
• Data will benefit future RockSAT and CubeSAT missions as a potential source of power
• Data will be used for feasibility study
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Concept of Operations• G-switch will trip upon launch, activating all
onboard power systems• Batteries power Arduino microprocessor and data
storage unit• Data collection begins
• Vibration and g-loads on piezo arrays create electric potential registered on voltmeter• Current conditioned to DC through full-bridge
rectifier and run to voltmeter• Voltmeter output recorded to internal memory• Data gathered throughout duration of flight
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Concept of Operations• Data acquisition and storage will enable
researchers to monitor input from multiple sources• XY-plane vibrational energy• Z-axis vibrational energy
• Researchers will determine if amount of power generated is sufficient for the power demands of other satellites
• Include visual verification of functionality• Use energy from piezo arrays to power small LED• Onboard digital camera will verify LED illumination
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Expected Results• Piezoelectric beam array will harness enough
vibrational energy to generate and store voltage sufficient to power satellite systems• Anticipate output of 130 mV per piezo
strip, based on preliminary testing.• Success dependent on following factors:• Permittivity of piezoelectric material• Mechanical stress, which is related to the
amplitude of vibrations• Frequency of vibrations
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Piezoelectric Power Output
Arduino Microcontroller
Camera
Power Supply
Rectifier
Piezoelectric Power Output
LEDRectifier
#1: 3-Axis Accelerometer
#2: 3-Axis Accelerometer
G-Switch
Rectifier Rectifier
Piezoelectric Power Output
Piezoelectric Power Output
Electrical Design
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Electrical Design continued
Piezoelectric Wire Output
LED
EPS Power Supply
Camera
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Software Elements
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Software Elements continued
Input Output Purpose
G-Switch T/F True/False Write to SD when TAccelerometer 1 X
Voltage OutputsAll data output to SD card
via “write to file” command
Data CollectionAccelerometer 1 Y Data CollectionAccelerometer 1 Z Data CollectionAccelerometer 2 X Data CollectionAccelerometer 2 Y Data CollectionAccelerometer 2 Z Data CollectionBridge Rectifier 1 Data Collection
Bridge Rectifier 2 Data Collection
Time (>1000s?) True/False End write command when T
Changes and UpdatesKelly Collett
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Subsystem IdentificationEPS – Electrical Power Subsystem
• Includes Arduino microprocessor, g-switch, accelerometers, voltmeter, battery power supply, and all related wiring
STR – Structural Subsystem• Includes Rocksat-C decks and support columns
PEA – Piezoelectric Array Subsystem• Includes piezoelectric bimorph actuators, cantilever
strips, mounting system, rectifier, and related wiring
VVS – Visual Verification Subsystem• Includes digital camera, LED, and all related wiring
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Physical Layout
XY-plane and Z-axis PEA (top),ZX-plane PEA (left), and “Nonlinear” PEA
(right)
PEA orientation updates on lower flight deck, full assembly shown
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Personnel UpdatesTeam• Kelly Collett – VVS, Testing• Christopher Elko – STR, PEA• Danielle Jacobson – EPS,
ManufacturingAdvisor• Dr. Jin KangNEW – Mentee• Ian Bournelis
• Pre-Junior (grad 2014)• Will be present at
Wallops to help with testing and integration
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Schedule UpdatesSchedule• Currently on track• Looking to start full
system testing as early as the end of this week (Feb. 17)
Concerns• Vibe testing
Subsystem Test ReportChristopher Elko
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Subsystem OverviewPEA – Piezoelectric Array Subsystem – ChristopherSTR – Structural Subsystem – ChristopherEPS – Electrical Power Subsystem – DanielleVVS – Visual Verification Subsystem – Kelly
Piezoelectric Array SubsystemChristopher Elko
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Analysis revisited
PEAStress Analysis• Point load
to simulate mass at end
• Uniform load to simulateG-loading
• Maximum stress doesnot exceed 2000 psi
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Analysis revisited
PEADeformation
Analysis• Point load
to simulate mass at end
• Uniform load to simulateG-loading
• Maximum deformation:0.3 inches
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Analysis revisited
STRStress Analysis• Point load
at electronic elements
• Uniform load to simulateG-loading
• Maximum stress doesnot exceed 649.6 psi
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Analysis revisited
STRDeformation
Analysis• Point load
at electronic elements
• Uniform load to simulateG-loading
• Maximum deformation:0.92 inches
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Preliminary Testing revisited
Preliminary piezo strip actuator voltage testing
for PEA design
Preliminary piezo strip actuator LED testing for
PEA-VVS interaction
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Non-Destructive TestsLow-Amplitude Random Vibration• Entire PEA subsystem assembled on lower deck
and subjected to random vibrations.• Range of output observed and recorded.
Random Vibration Voltage Output Data
Z-axis XY-plane ZX-place Nonlinear
Output Range (VAC) 0.13 - 0.168 0.046 - 0.102 0.024 - 0.042 0.073 - 0.131
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Non-Destructive Tests continued
Low-Amplitude Random Vibration• Lessons learned
• Due to relatively low magnitude of vibration shock (< 1G), actuators did not reach maximum output
• Masses must be added to improve low-G response, wait to vibe test with higher amplitudes to decide
• Higher specific voltage output with deflection of “nonlinear” simply supported beam• Architecture promotes higher magnitude of elongation
strain than free-ended cantilevers
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Non-Destructive Tests continued
PEA Wiring Connection Test• Determination of wiring scheme
• Connected actuators in series, then in parallel• Subjected to random deflection to find optimal scenario
• Lessons learned• Better to keep each piezo line separate• Because of random vibration, output of one actuator can be
out-of-phase with another’s, leading to destructive interference
• Also enables specific output to be more closely monitored and correlated with accelerometer data
• Consider adding capacitors to smooth out voltages
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Destructive TestsPEA Fracture Test• Determination of bending
limits of piezoelectric bimorph actuator strips• Secured strip to flat surface
with clamp• Put end of spindle
micrometer in contact with free end of strip, noting starting point
• Gradually tightened micrometer to failure point of strip PEA Fracture Test setup.
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Destructive Tests continued
Deflection Notes
1 mm No sign of fracture.
2 mm Design deflection.
3 mm No sign of fracture.
4 mm More torque required.
5 mm Protective layer begins tearing.
6 mm Audible “crackle” ≈ 5.85 mm.
7 mm Increased frequency of crackling
8 mm Tearing becoming visible.
9 mm More audible crackling.
10 mm More audible crackling.
12 mm Voltage output compromised.Will it break?
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Destructive Tests continued
PEA Fracture Test• Lessons learned
• PZT-copper-PZT sandwich designed for maximum deflection of approximately 2 mm without degradation in output
• Actual safe deflection found to be approximately 5.6 mm, on average
• Audible PZT fracture began between 6 and 8 mm of deflection, and continued to end of test, around 13.5 mm
• Despite degradation of PZT crystalline structure, output of fractured actuators remained impressively high, with only about a 40% loss in potential compared to non-deformed strips.
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Thermal TestsThermal Adhesive Tests• Thermal tests will be used to determine thermal
expansion of the piezos once adhered to the cantilever. This will ensure that the piezos don’t crack once adhered.
• Results will determine adhesive to be used.• Test Plan
• Adhere piezo actuator to cantilever material• Subject assembly to cyclic thermal environment• Bake in oven, then put in freezer
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Thermal Tests continued
Thermal Adhesive Tests
• Oven heated to 385°F• Freezer steady at 25°F• No noticeable effects
on cantilever integrity• Piezoelectric strip
exhibited no apparent degradation in output
Piezo cantilever assembly in oven (top) and freezer (bottom)
Electrical Power SubsystemDanielle Jacobson
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Arduino Sampling RatesChanged sampling rates from 300 bps to 115,200 bps
Program to test data transmission: 110,000 charactersData transmits flawlessly at 9600 bps
Default rate of our SD card breakout chip
9600 bps 115200 bps
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Data CollectionOver 140 iterations for data recordingVoltage of 3.3V = 686 in data file V= α*OutputWhere α = 0.0048
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G-Switch Program TestDemonstrative Video• If you would like to see the video, we would be
happy to send it to you as a separate file!• File is ~57MB
Visual Verification Subsystem
Kelly Collett
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VVS SubsystemCamera Activation• Tests will ensure camera
relays function properly.• Power down
requirement includes camera. Camera will be relayed to g-switch to be activated upon launch.
• Test Plan• Connect camera to G-
switch, click system on and check that camera turns on and records.
• Check that video saves at the end.
41
VVS SubsystemLessons Learned• Good solder connection
is crucial• Hot glue everything!
• Camera has wide Field of View• Not a bad thing, but
something we weren’t expecting
We’d put a video here, but it’s ~40MB.
If you’d like to see it let us know and we can send it separately.
Conclusions
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Subsystem IntegrationPlan:• Hoping to integrate everything next week
• We already integrated the PEA and VVS subsystems with the EPS for testing, everything else is mostly hardware and mounting releated
Concerns:• Vibe testing
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Full System TestingVibration Testing• Tests will ensure system is structurally sound
during vibration.• Test Plan
• Construct and connect full system• Use vibe table to simulate Terrier-Orion flight
vibration conditions• Monitor system connections and structural
integrity throughout test• Check for data collection on Arduino board and
camera at end of tests
45
Full System TestingSpin Testing• Tests will ensure system is structurally sound
during spin.• Test Plan
• Construct and connect full system• Use spin table to simulate spin of Terrier-Orion
rocket• Monitor system connections and structural
integrity throughout test• Check for data collection on Arduino board and
camera at end of tests
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Lessons LearnedWhat was learned• Programming takes forever.• Solder joints are fragile—reinforce with hot glue.• Don’t put twinkies on your pizza.Do differently• Measure twice, cut once.• Have an EE member on the team.What’s worked well• Coffee. Lots of coffee.
Final Thoughts
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AcknowledgementsReuben Krutz for assistance and guidance with programming
Marc Gramlich for assistance with camera teardown and integration
Brandon Terranova & Tyler Douglas for allowing us borrow their lab’s precision solder station and helping set up destructive testing
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RecapConcerns• Vibe testing
Thank you!Questions?
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