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Drexel University 2010-2011 RockSat-C Critical Design Review. Joe Mozloom Eric Marz Linda McLaughlin Swati Maini Swapnil Mengawade Advisor: Jin Kang, PhD. Mission Overview - Objective. - PowerPoint PPT Presentation
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Drexel University Rock-Sat 1
Drexel University2010-2011 RockSat-CCritical Design Review
Joe MozloomEric MarzLinda McLaughlinSwati MainiSwapnil MengawadeAdvisor: Jin Kang, PhD
Drexel University Rock-Sat 2
Mission Overview - Objective
Drexel's RockSat payload will incorporate a platform rotating opposite the spin-stabilization of the Terrier-Orion sounding rocket during ascent, resulting in a rotationally static platform from an outside reference frame.
Drexel University Rock-Sat 3
Mission Overview - Purpose
Experimentally determine the feasibility of a despun platform under high acceleration and turbulence, driven by a low power system.
Provide a stable platform with respect to the exterior environment to accommodate experiments requiring constant frame of reference in an ascending object.
Drexel University Rock-Sat 4
Team Overview
Advisor: Dr. Jin Kang, PhD.
MEM Department, Drexel University
Team Leader : Joe Mozloom
Senior, Drexel University
Subsystem Head: Despun Platform
Team MembersName Eric Marz Linda McLaughlin Swati Maini Swapnil Mengawade
Year and Major
Senior, Electrical and Computer Engineering
Senior, Electrical and Computer Engineering
Senior, Mechanical Engineering and Mechanics
Senior, Mechanical Engineering and Mechanics
Subsystem Head
Micro-controller, Storage and G-switch
Sensors, DAC and Power Systems
Motor System and Organization
Modeling, System level requirements and Compliance to User guide
Drexel University Rock-Sat 5
Concept of Operations
There are several flight points which are of interest to our experiment (Seen on next slide)
Rotation measurements of despun platform during following time periods: Terrier Burnout Orion Burnout Remaining Ascent Descent
Drexel University Rock-Sat 6
Concept of Operations
Drexel University Rock-Sat 7
Expected Results
Workbench FlightConform to all NASA/WFF requirements as outlined in User Guide
Conform to all NASA/WFF requirements as outlined in User Guide
Counter-rotating platform effective over outer canister spin frequency range from 0.5 Hz - 10 Hz
Counter-rotating platform engaged when canister is spinning
Maximum platform spin-rate 10% of current canister spin-rate
Platform able to rotate under harsh flight conditions
Data stored in memory and accessible post test
Data stored in memory and accessible post flight
Drexel University Rock-Sat 8
De-Scope
Initial Goal to provide a rotationally stable platform and perform experiment on our despun platform.
De-Scoped to be a feasibility study for our despun platform design.
Reasoning If despun platform failed, experiment on platform
would produce no useful results.
Drexel University Rock-Sat 9
Off Ramps
Polycarbonate Plate -> Acrylic Plate Polycarbonate is more difficult to machine, if we are
unable to CNC a usable geared platform and pinion then Acrylic will be cut via laser cutter.
Digital to Analog Converter (DAC) Initially designed to be created out of a resistor ladder. If
precision cannot be easily obtained through this, an aftermarket DAC could be used.
Closed Loop Algorithm -> Open Loop Algorithm Can simplify algorithm to not take into account despun
platform sensor if there are difficulties.
Drexel University Rock-Sat 10
Mechanical Design Elements
Drexel University Rock-Sat 11
Mechanical Design
Drexel University Rock-Sat 12
Labeled Diagram
1.2 V AAA Battery
Upper platform
Gear
Accelerometer
G-switch
Microcontroller board
1.25
2.0
1.0
5.09.3
1 Unit: Inches
Drexel University Rock-Sat 13
Labeled Diagram
Slip ring holder
Slip ring
Motor holder
MotorDAC
4.75
2.75
Unit: Inches
Drexel University Rock-Sat 14
Manufacturing Plan
Gear Polycarbonate CNC Milled
Pinion Polycarbonate CNC Milled
Slip Ring Holder ABS 3D Printed
Motor Mount ABS 3D Printed
Platforms (2X) Polycarbonate CNC Milled
Drexel University Rock-Sat 15
Procurement Plan
Slip Ring (Received) Motor (Received) Polycarbonate sheets
12”x12”x 0.5” 12”x24”x0.25”
Standoffs 8-32 x ¼” x 4”
Bolts (8-32, 0-80, M3)
Drexel University Rock-Sat 16
Current Position
All parts have been ordered Slip Ring and Motor have arrived
1st Iteration of prototyping is completed Main objective: Sizing/Fit verification
• Slip Ring Holder• Motor Mount• Gear• Pinion
2nd Iteration of prototyping has begun Altering design for better fit, wire accommodation, etc
Drexel University Rock-Sat 17
Changes Since PDR
Slip Ring Holder and Motor Mount defined The 5x 9V batteries are replaced by 10x 1.2V
AAA batteries The components on fixed platform defined to
adjust COG
Drexel University Rock-Sat 18
Electrical Design Elements
Drexel University Rock-Sat 19
Electronics Schematic
Power Supply
StationaryAccelerometer Microcontroller
DespunAccelerometer Slip Ring
Digital to AnalogConverter Motor
Drexel University Rock-Sat 20
Manufacturing /Procurement Plan
Manufactured DAC
Soldered Sensors Small electronics
• Resistors, capacitors, diodes Procured
Microcontroller purchased with integrated Control Board
Hi G and Low G Accelerometers 10 NiMH rechargeable AAA Batteries G-Switch
Drexel University Rock-Sat 21
ATmega32 Control Board
"Mini AVR ATmega32 Board Schematic." Micro4You. Web. 1 Dec. 2010. <http://www.micro4you.com/store/mini-AVR-ATmega32-Board/prod_155.html>
Microcontroller Communications
Microcontroller and Power Connections
MicrocontrollerExternal Ports
Reset and Power LED
Drexel University Rock-Sat 22
DAC Design 8-Bit(Subject to Off-Ramp and Improvement)
Out to Motor Control
Drexel University Rock-Sat 23
DAC Design
8-Bit DAC Initial Design Allows for 0.148 Hz Steps (Taking into account our
motor specifications and gear ratio) 10-Bit DAC
Plan if more precision needed after initial testing Allows for 0.037 Hz Steps More difficult to control through our microcontroller’s
8-bit ports. Simple Modification from 8-bit design.
Drexel University Rock-Sat 24
Software Design Elements
Drexel University Rock-Sat 25
Software UML Diagram
Drexel University Rock-Sat 26
Software FlowMajor Code Blocks
Fixed Platform Sensor Data Read 10 Times per second sample fixed platform sensor data and
calculate rocket rotation. Despun Platform Sensor Data Read
10 Times per second sample despun platform sensor data and calculate platform rotation.
Data Storage 10 Times per second store both Fixed Platform and Despun
Platform sensor data with timestamps. Motor Control
When either fixed platform sensor or despun platform sensor values are above threshold, adjust motor RPM through DAC.
Drexel University Rock-Sat 27
Analysis & Prototyping
• FEA Analysis (Stress/Deformation)• Tooth Loading, Gear/Pinion• Vertical Loading, Gear/Pinion• Vertical Loading, Motor Mount
• Electronic Simulation• DAC Simulation in PSPICE
• Physical Prototyping• Gear• Pinion• Slip Ring Mount (top / bottom)• Motor Mount
Drexel University Rock-Sat 28
Gear/Pinion Tooth FEA
10 N Horizontal Load Applied to Single Tooth Face Theoretical load
calculation = 1.26 N• Based on Moment of
Inertia of gears and elevated frictional forces in bearings at 25 G
Fixed at 2x 0-80 Set Screw Holes
Drexel University Rock-Sat 29
Gear/Pinion Tooth FEA Results
Gear Pinion
Theoretical Load (N) 1.26 1.26
Load Applied (N) 10 10
Max Deflection (mm) .026 .012
Max Stress (MPa) 1.788 1.081
Max Stress Location Set Screw Holes Set Screw holesFilet of loaded tooth
Safety Factor 34.7 57.4
Drexel University Rock-Sat 30
Vertical Loading FEA
Loading based on mass of component and multiply by 25G
Loading distributed across top face of component
Tested for Max Stress and Vertical Deflection
Drexel University Rock-Sat 31
Vertical Loading FEA Results
Gear Pinion Motor Mount
Theoretical Load (N) 25 2.5 49
Load Applied (N) 50 5 100
Max Deflection (mm) 0.01 0.001 0.243
Max Deflection Location Outer Diameter Outer Diameter Top Face Inner
Diameter
Max Stress (MPa) 2.741 0.135 9.715
Max Stress Location Set Screw Holes Set Screw Holes and ID
Top face ID at mounting holes
Safety Factor of Applied Load 23.7 459.7 6.7
Drexel University Rock-Sat 32
Prototyping Results
Slip Ring Holder (Top and Bottom) Prototyped with Fuse
Deposition Rapid Prototyping Machine
Verifies fit and sizing and integration of design
Motor Mount Prototyped with Fuse
Deposition Rapid Prototyping Machine
Verify fit and sizing and integration of design
Drexel University Rock-Sat 33
Prototyping Results
Gear Laser Cut from .2”
Acrylic Verifies tooth design
mating with pinion Pinion
Laser Cut from .45” Acrylic
Verifies tooth design mating with gear
Drexel University Rock-Sat 34
Center of Gravity
Center of Gravity: ( inches )X = 0.20Y = -0.88Z = 0.96
Drexel University Rock-Sat 35
Mass BudgetComponent Mass (Kg)
Lower Platform Weight 0.268
Upper Disk 0.105
Slip Ring 0.077
Slip Ring Base 0.040
Battery Case 0.045
Battery (1×10) 0.013×10 = 0.130
Accelerometers 0.025
Microcontroller 0.050
Wiring 0.020
Bolts (1×6) 0.030×6 = 0.180
Nuts (1×6) 0.015× 6 = 0.09
Motor 0.193
Motor base 0.050
G-switch 0.015
Total 1.288
Mass (Kg)
Mass Allowance 2
Theoretical Mass 1.288
Mass Margin 0.722
Drexel University Rock-Sat 36
Power Budget
Sub System Voltage (V) Current (A) Operating Time (min) Ampere Hour
Motor 12.0 4.0 10 0.65
High G Accel. 3.0 - 6.0 1.1m 10 0.0011
Low G Accel. 4.75 - 5.25 2.9m 10 0.0029
Microcontroller 2.7 - 5.5 2.2m 10 0.0022
Total 0.6562
Drexel University Rock-Sat 37
Testing Plan
System Testing
Mechanical Testing
Electrical Testing Sensor Testing
Data Testing
Drexel University Rock-Sat 38
System Level TestingSystem Requirement Physical Test Success CriteriaConform to all NASA/WFF requirements as outlined in User Guide
Measure Mass & Volume
Counter-rotating platform effective over outer canister spin frequency range from 0.5 Hz - 10 Hz
Spin final assembly at different spin ratesOutside measurement compared to stored data.
Despun Platform able to operate
Maximum platform spin-rate 10% of current canister spin-rate
Spin final assembly at different spin ratesOutside measurement compared to stored data.
Measure despun platform acceleration has max 10% of current canister acceleration
Experiment Should be able to survive launch conditions
Vibration Test at 2x flight conditions (50G)
System operational after test
Drexel University Rock-Sat 39
Mechanical Testing
All components will be individually measured for mass Masses will be summed to verify compliance
Vibration Testing at 2x Flight Conditions (50 G) Each Subsystem tested Final Assembly tested
Motor Mount to have vertical loading destructive testing to verify flight readiness
Drexel University Rock-Sat 40
Electrical Testing Battery Testing
Battery will be tested using the battery voltage method with a digital D.C. Voltmeter
Battery is fully charged before testing
Percent Charge Voltage [12V]
100% 12.7
75% 12.4
50% 12.2
25% 12.0
Discharged 11.9
Drexel University Rock-Sat 41
Sensor Testing ST pin test : the typical
change in output should be 750mV(750mg) ST pin test allows to verify if the
accelerometer is functional ST pin should never be exposed
to a voltage Vs+0.3 V If Vs=3V is used, the output
sensitivity is 560mV Vs= 4.75 V to 5.25 V, sensitivity
is 186 mV/g to 215 mV/g.
Drexel University Rock-Sat 42
Sensor Testing Self Test response in g: However if Vs≠5V, self test response
in volts is roughly proportional to the cube of the supply voltage.
Thus, at Vs=3V, self test response will be approximately equivalent to
150mV(270mg) Supply current decreases as the
voltage supply decreases. Typical consumption at VDD=3V is 450uA.
2VsH
ctekkVsH ,2
Drexel University Rock-Sat 43
DAC Testing
Differential non-Linearity Test(DNL) DNL is generally more critical when outputting small signals
To test the linearity of a DAC, we will generate the digital stimulus and capture the analog response.
DAC is swept from 000…0 to 111...1 DNL will show up as a change between each successive digital error output
Comparison between PSPICE simulations with real simulations will make improvements on DAC
Drexel University Rock-Sat 44
Risks
Drexel University Rock-Sat 45
DP - Risk Walkdown DP.RSK.1
Sensor will not function DP.RSK.2
Teeth on gear will break due to elevated torque levels from acceleration
DP.RSK.3 Vibrations will cause loss of contact in Slip
Ring Terminals DP.RSK.4
High Gs will cause slip ring bearings to seize DP.RSK.5
High Load causes gear to distort, losing contact with pinion
Walkdown FEA Analysis verifies distortion due to
vertical loading will be minimal
PROBABILITY
CONSEQUENCES
DP.RSK.3DP.RSK.5
DP.RSK.1DP.RSK.2 DP.RSK.2
DP.RSK.4DP.RSK.5
Drexel University Rock-Sat 46
MS - Risk Walkdown
PROBABILITY
CONSEQUENCES
MS.RSK.4 MS.RSK.2
MS.RSK.1MS.RSK.3 MS.RSK.1
MS.RSK.4 MS.RSK.2MS.RSK.3
MS.RSK.1 Motor-Battery
Communication Failure MS.RSK.2
Motor gear head and platform may lose contact under 25G
MS.RSK.3 Battery unable to sustain
variable rpm requirements MS.RSK.4
Motor may not respond to the micro-controller signals correctly.
Drexel University Rock-Sat 47
DS - Risk Walkdown DS.RSK.1
Microcontroller Power Failure DS.RSK.2
Despun Accelerometer Communication Failure
DS.RSK.3 Microcontroller can’t survive launch
conditions
Walk-Down Microcontroller with previous
launch experience selected to limit DS.RSK.5
Secure housing for slip ring designed to protect data transmission
PROBABILITY
CONSEQUENCES
DS.RSK.1 DS.RSK.3 DS.RSK.3
DS.RSK.2 DS.RSK.2
Drexel University Rock-Sat 48
New Risks
PROBABILITY
CONSEQUENCES
New.RSK.1
New.RSK.3 New.RSK.2
New.RSK.1 Bolts become loose during
launch New.RSK.2
Components come in contact with the vibrating canister wall
New.RSK.3 Motor or Sensor
communication Failure with Microcontroller
Walk-Down Caps could be used on bolts Minimizing placement of
components near canister wall Using hard Soldering for
connections
Drexel University Rock-Sat 49
User Guide Compliance
G-Switch will be used for system activation No ports will be required No plans for high voltage
Mass (Kg)
Mass of Experiment 1.288
Mass of Canister 3.134
Total 4.422
Payload Mass Requirement 6.35
Drexel University Rock-Sat 50
Shared Can Logistics
Sharing ½ can with Temple University Drexel on bottom half, Temple on top half
Temple University will be measuring gamma and x-rays, up to 100keV, through the use of a scintillator and photomultiplier-tube. They will use visible solar light as a directional z-axis reference point to characterize the high energy particles as solar or cosmic rays.
Both experiments to be separated via two individual platforms (top and bottom)
Recovery and AnalysisWallops Island Flight facility
Weekely Teleconference 9Weekly Teleconference 8 (LRR)
Launch Readiness Review (LRR) TeleconferenceWeekly Teleconference 7
Second Full Mission Simulation Test Report DueWeekly Teleconference 6Weekly Teleconference 5Weekly Teleconference 4
Fit Check with TempleWeekly Teleconference 2Weekly Teleconference 3
Mission Simulation and TestingAsembly Vibration TestingWeekly Teleconference 1
Final Installment DueAssembly Spni Testing
Payload Subsystem Integration and Testing Report TeleconferencePayload Subsystem Integration and Testing Report Due
Online Progress Report 4 DueSubsystem Assembly
Individual Subsystem Testing Report TeleconIndividual Subsystem Testing Reports Due
Online Progress Report 3 DueDestructive Testing of Motor Mount
Vibration Testing of SubsystemsRockSat Payload Canisters Sent to Customers
Machining of Mechanical ComponentsBuild Dac
CAM Coding Development and TestingFlight Selections
Subsystem ConstructionMicrocontroller Programing
Critical Design Review (CDR) Due3D Printing Prototyping
Online Progress Report 2 DueGear Prototyping
Receive PartsOrder Parts
Preliminary Design Review (PDR) TeleconferenceSource Parts
Iterative Design Process
9/15/2010
10/15/2010
11/14/2010
12/14/2010
1/13/2011
2/12/2011
3/14/2011
4/13/2011
5/13/2011
6/12/2011
Start Date
Completed
Remaining
Drexel University Rock-Sat 52
BudgetItem Part Number Manufacturer Vendor Quantity Unit Price ($) Total ($)
Dual Axis Accelerometer AT26DF161A Analog Devices Analog Devices 2 12 24
Integrated Board/ ATMega32 Microcontroller MINWST7N47 Atmel micro4you.com 1 28 28
Slip Ring CAY-1847 Aeroflex Aeroflex 1 400 400
G-Switch ASDX015A24R Atmel Digi-Key 1 25 25
DC Micro-motor 3242-SCDC Faulhber Micromo 1 345 345
12"x12"x0.50" PC Sheet 8574K32 - McMaster-Carr 1 28 28
12"24"x0.25” PC Sheet 8574K43 - McMaster-Carr 2 20 20
Flash Memory AT26DF161A Atmel Digi-Key 1 4 4
AAA NiMH Rechargeable Battery 16546 Accupower onlybatteries.com 12 3.25 39
2" Standoffs 92745A369 McMaster-Carr McMaster-Carr 8 1.12 8.96
1/8" Standoffs 91780A191 McMaster-Carr McMaster-Carr 4 0.029 0.116
Various Bolts 10
Totals 932.076
Conclusion
Issues Unsure if re-chargeable batteries can be used Holder materials ABS or metal- steel, aluminum Temple may not be using center standoff
(Drexel will include center standoff)Plan of action Currently prototyping parts On receiving shipments, assembly of parts to
be ready for testing.