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Drexel RockSAT

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  1. Drexel RockSAT Critical Design Review • Kelly Collett • Christopher Elko • Danielle Jacobson • December 8, 2011

  2. PDR Presentation Contents • Section 1: Mission Overview • MissionStatement • Mission Requirements • Mission Overview • Concept of Operations • Expected Results

  3. PDR Presentation Contents • Section 2: Design Description • Off-ramps • Physical Model • Mechanical Design • Electrical and Software Design • Section 3: Prototyping and Analysis • Mechanical Subsystems • Electrical Subsystems • Mass Budget • Power Budget

  4. PDR Presentation Contents • Section 4: Manufacturing Plan • Mechanical Elements • Electrical and Software Elements • Section 5: Testing Plan • PEA Subsystem • EPS Subsystem • VVS Subsystem • Total System Testing

  5. PDR Presentation Contents • Section 6: Prototype Risk Assessment • PDR Risk Walk-down • Top CDR Risks • Section 7: User’s Guide Compliance • Section 8: Project Management • Organizational Chart • Schedule • Budget • Sharing Logistics

  6. Mission Overview Drexel RockSat Team 2011-2012

  7. 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.

  8. Mission Requirements

  9. 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

  10. 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

  11. 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

  12. 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

  13. Design Description Christopher Elko

  14. 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

  15. Off-Ramps VVS • Main concern: Camera activation • Relaying the camera to the g-switch for activation after launch will likely prove difficult. • If this cannot be achieved on time, the VVS will be removed from the payload. • This will drop the mass of the payload significantly, and will require additional ballast in its place.

  16. Physical Model Accelerometer Array Power Supply Microcontroller G-Switch Bridge Rectifiers Flight Decks Camera Standoff Supports Verification LED Piezo Arrays

  17. Canister Fitment Canister Partner’s Space Allowance 10.0” 4.313”

  18. Mechanical Design STR Clear Acrylic Flight Decks Stainless Fasteners 8-32 threadx 3/8” long QTY = 10 ¼” thick 9.29” dia. QTY = 2 Aluminum Standoffs Fifth standoff column included to provide support for EPS electronics mountedto top deck. 5/16” hexx 2 ¼” long QTY = 5

  19. Mechanical Design PEA Piezoelectric Strip Fasteners PZT Ceramic 40 mm x 10 mm 5 mm thick Support Block Aluminum Cantilever 2 ¼” x ½” 0.040” thick Different orientations account for vibrations in multiple planes.

  20. PEA Design continued Mounted to Lower Deck Use 4-40 x 3/8” Screws

  21. Electrical Design LED LED Piezoelectric Power Output Piezoelectric Power Output Rectifier Rectifier Camera Low-G Accelerometer Arduino Microcontroller High-G Accelerometer High-G Accelerometer Low-G Accelerometer G-Switch Power Supply

  22. Electrical Design continued Piezoelectric Wire Output LED Camera EPS Power Supply

  23. Electrical Elements To Bridge Rectifier • Powered by 4 AA batteries • Connects directly to microcontroller • Modified to incorporate G-switch Piezo Arrays (Battery) LED G-Switch To Bridge Rectifier Microcontroller Battery Pack PEA-VVS Circuit Diagram G-switch interface with EPS

  24. Electrical Elements continued Low-G Accelerometer High-G Accelerometer

  25. Electrical Elements continued Bridge Rectifier #1 Piezo Array 1 Bridge Rectifier #2 Piezo Array 2

  26. Electrical Elements continued • Breadboard used for SD card and Arduino microcontroller integration http://www.electronics-lab.com/blog/?m=200806

  27. Electrical Elements continued • Two breadboards • LED circuit • SD card integration • Allowance of 15-20 iterations to debug electronics • Limited previous exposure to programming microcontrollers and EE in general • All electrical elements have been procured • Four dual-axis accelerometers have been replaced with two three-axis accelerometers

  28. Software Elements

  29. Software Elements continued

  30. Accelerometer Pseudo-Code

  31. SD Card Data Storage Code: Complete

  32. Prototyping and Analysis Christopher Elko

  33. Prototyping • PEA • Preliminary test setup measured voltage levels from a single strip actuator under deformation using a digital voltmeter. • Results suggest adequate voltage potential for entire system, with an average of approximately 132 mVAC generated by a single actuator. • Preliminary finite element analysis results in ABAQUS suggest aluminum is adequate for resistance to cyclic loading in this application. • Mechanical analysis, in conjunction with destructive testing of piezo actuators, will optimize dimensions of support cantilever dimensions.

  34. Prototyping continued • STR • Preliminary FEA results suggest a fifth aluminum standoff is desirable for added support of electronic components on upper deck. • Currently finalizing design and interactions with PEA mounting methods. • EPS • SD card adapter to be integrated • Accelerometers integrated into microcontroller and tested for data output • VVS • Tested LED circuit for functional interaction with PEA

  35. Prototyping continued Preliminary piezo strip actuator voltage testing for PEA design Preliminary piezo strip actuator LED testing for PEA-VVS interaction

  36. Analysis cantilever deflection Point Load Distributed Load • Maximum deformation at end of beam, where x = L • Combined loadingduring flight due toG-loading and massat end of beam

  37. Analysis FEA • PEA • Stress Analysis • Point loadto simulate mass at end • Uniform load to simulateG-loading • Maximum stress doesnot exceed 2000 psi

  38. Analysis FEA • PEA • Deformation Analysis • Point loadto simulate mass at end • Uniform load to simulateG-loading • Maximum deformation:0.3 inches

  39. Analysis FEA • STR • Stress Analysis • Point loadat electronic elements • Uniform load to simulateG-loading • Maximum stress doesnot exceed 649.6 psi

  40. Analysis FEA • STR • Deformation Analysis • Point loadat electronic elements • Uniform load to simulateG-loading • Maximum deformation:0.92 inches

  41. Mass Budget

  42. Power Budget

  43. Manufacturing Plan Choose your weapon

  44. Mechanical Elements • STR • Acrylic plate laser-cut to size/shape of flight decks • Flight decks among first components manufactured to ensure proper interaction with other subsystems • PEA • Cantilevers cut to size from sheet aluminum upon determining optimum • Piezo actuators to be bonded to cantilevers • Mounting blocks and deflection limiters must be custom-milled from aluminum stock

  45. Electrical Elements • EPS • Electronic interfaces will be table-tested with breadboard and reconfigurable components • Testing will help to determine system capabilities • VVS • Testing will help to determine system capabilities and effects on other subsystems

  46. Software Elements • Code to be finalized • Accelerometers • Voltage output from bridge rectifiers • SD card data recording • Code to be developed • Power loop for camera • G-switch • Code block dependencies • SD card code integrates all subroutines • All code dependent on “true” output from G-switch

  47. Testing Plan Choose wisely.

  48. PEA Subsystem Piezo Actuator Tests Non-destructive Testing • Non-destructive testing will determine voltage output from piezo actuators. • Test Plan • Connect actuators to voltmeter, LEDs; flex actuators to generate current Destructive Testing • Will determine bending deformation limits of piezo actuators. • Test Plan • Use spindle micrometer to bend piezos until fracture.

  49. PEA Subsystem continued Cantilever Tests Unrestricted Cantilever • Unrestricted cantilever testing will determine max deformation limits of cantilevers and whether or not a block is needed to restrict deformation. • Cantilevers will be designed so that they bend freely with only slight vibration. • Test Plan • Set up cantilever assembly on vibe table • Measure deflection using high speed camera

  50. PEA Subsystem continued Cantilever Tests continued Restricted Cantilever • Restricted cantilever testing will ensure that designed block will restrict deformation as needed such that PEA won’t deform past piezo deformation limits. • Block will be designed to restrict deformation in the + and – axis. • Test Plan • Same as unrestricted tests except for use of block.