Drexel RockSAT

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

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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.

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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

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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?