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Drexel RockSAT Individual Subsystem Testing Report • Kelly Collett • Christopher Elko • Danielle Jacobson • February 12, 2012
ISTR Presentation Contents • Section 1: Mission Overview • MissionStatement • Mission Objectives • Expected Results • Functional Block Diagrams • Section 2: Changes and Updates Since CDR • System Modifications • Project Management & Team Updates • Schedule Updates
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 Overview Drexel RockSat Team 2011-2012
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.
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
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
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
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
Electrical Design Piezoelectric Power Output Piezoelectric Power Output Piezoelectric Power Output Piezoelectric Power Output LED Rectifier Rectifier Rectifier Rectifier Camera Arduino Microcontroller #1: 3-Axis Accelerometer #2: 3-Axis Accelerometer G-Switch Power Supply
Electrical Design continued Piezoelectric Wire Output LED Camera EPS Power Supply
Changes and Updates Kelly Collett
Subsystem Identification • EPS – 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
Physical Layout PEA orientation updates on lower flight deck, full assembly shown XY-plane and Z-axis PEA (top), ZX-plane PEA (left), and “Nonlinear” PEA (right)
Personnel Updates • Team • Kelly Collett – VVS, Testing • Christopher Elko – STR, PEA • Danielle Jacobson – EPS, Manufacturing • Advisor • Dr. Jin Kang • NEW – Mentee • Ian Bournelis • Pre-Junior (grad 2014) • Will be present at Wallops to help with testing and integration
Schedule Updates • Schedule • Currently on track • Looking to start full system testing as early as the end of this week (Feb. 17) • Concerns • Vibe testing
Subsystem Test Report Christopher Elko
Subsystem Overview • PEA– Piezoelectric Array Subsystem – Christopher • STR – Structural Subsystem – Christopher • EPS – Electrical Power Subsystem – Danielle • VVS – Visual Verification Subsystem – Kelly
Piezoelectric Array Subsystem Christopher Elko
Analysis revisited • PEA • Stress Analysis • Point loadto simulate mass at end • Uniform load to simulateG-loading • Maximum stress doesnot exceed 2000 psi
Analysis revisited • PEA • Deformation Analysis • Point loadto simulate mass at end • Uniform load to simulateG-loading • Maximum deformation:0.3 inches
Analysis revisited • STR • Stress Analysis • Point loadat electronic elements • Uniform load to simulateG-loading • Maximum stress doesnot exceed 649.6 psi
Analysis revisited • STR • Deformation Analysis • Point loadat electronic elements • Uniform load to simulateG-loading • Maximum deformation:0.92 inches
Preliminary Testing revisited Preliminary piezo strip actuator voltage testing for PEA design Preliminary piezo strip actuator LED testing for PEA-VVS interaction
Non-Destructive Tests Low-Amplitude Random Vibration • Entire PEA subsystem assembled on lower deck and subjected to random vibrations. • Range of output observed and recorded.
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
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
Destructive Tests PEA 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.
Destructive Tests continued Will it break?
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.
Thermal Tests Thermal 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
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 Subsystem Danielle Jacobson
Arduino Sampling Rates Changed sampling rates from 300 bps to 115,200 bps Program to test data transmission: 110,000 characters Data transmits flawlessly at 9600 bps Default rate of our SD card breakout chip 115200 bps 9600 bps
Data Collection Over 140 iterations for data recording Voltage of 3.3V = 686 in data file V= α*Output Where α = 0.0048
G-Switch Program Test Demonstrative 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
VVS Subsystem Camera 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.
VVS Subsystem Lessons 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.
Subsystem Integration Plan: • 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
Full System Testing Vibration 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
Full System Testing Spin 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
Lessons Learned • What 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.
Acknowledgements • Reuben Krutzfor 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
Recap • Concerns • Vibe testing
Thank you! Questions?