Title: Project Design Review DIABLO De-rotated Imager of the Aurora Borealis in Low-earth Orbit
1Project Design ReviewDIABLODe-rotated Imager of
the Aurora Borealis in Low-earth Orbit
Lang Kenney Nick Pulaski Matt Sandoval Tim
Sullivan
- Nicole Demandante
- Laura Fisher
- Jason Gabbert
- Lisa Hewitt
Image taken from Space Shuttle over South Pole
http//www.geo.mtu.edu/weather/aurora/images/space
/
2Agenda
- Background, objectives, requirements
- System Design Alternatives
- System Design-To-Specifications
- Subsystem Design Alternatives
- Project Feasibility and Risk Assessment
- Project Management Plan
3Background
- Initial Idea LASP - Monitor Proposal
- Scientific Purpose Visible light images and
in-situ observations
4Objective
- Objective Provide a spinning satellite with a
de-rotated imaging system - Deliverables
- De-rotated imaging assembly
- Spinning test bed
- Control loop
- Goal
- Achieve the least amount of smear in the image
- Model final fight spacecraft
5System Level Design-to-Specs
- The system shall
- Optical System
- Take pictures at 90
- Pointing within 3
- Field of view minimum of 6
Optical Axis
Spin Axis
12
3
Earth
6System Level Design-to-Specs
- Control Loop
- Pixel smear - Images can be resolved to better
than 1 pixel per kilometer - Sun-shading Assembly
- No direct sunlight between 60 and 90 latitude
- Test System
- Test bed range 2 20 rpm
- Offset Test Tilt 1 relative to test bed
- Test camera resolution to shutter speed ratio
similar to flight camera
Changed from PDD, customer approved
7System Designs
- Optical and Spin Axis Alignment
- Design will be used by customer
8System Designs
Spin axis
Spin direction
Cameras
Cameras
Booms
9System Designs
10System Level Design Comparison
Image Clarity (22) Complexity (15) Fabrication (15) Ease of Verification (15) Moment of Inertia (10) Mass (10) Comparable to Actual Satellite (13) Total Score
Fixed Camera 1 10 9 7 2 2 1 4.64
Passive 3 8 9 1 9 10 1 5.47
Rail Car 7 3 5 7 5 6 6 5.66
Parallel Plate 7 6 6 7 5 6 4 6.00
Axis Alignment 8 7 7 7 7 8 8 7.45
Fixed Camera
Passive Stabilization
Axis Allignment
Rail Car
Parallel Plate
For more detail see slides 41 - 46
11Subsystems
- Optical
- Rotation
- Structure
- Electronics Sensors
- Controls Data Acquisition
- Power
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13Sizing
- Actual spacecraft will use two de-rotated
assemblies
r
R 0.75 1 m
Design-To Radius
R0.75-1m
- Actual test platform does not need to be this
large so long as the height - is sufficient to meet above requirement
14Arrangement
- Requirements on flight camera
- Long focal length (10cm)
- Thermal shielding
- Radiation shielding
- Moment of Inertia
- Camera Choice COTS point and shoot
For more detail on camera choice, see slide 47
15Resolution
Operating Range -90 to -60 and 60 to
90 Depends on Orientation of Orbit
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17Precision Motor Options
- Direct Drive Servo Motor Stepper
Motor Brushless Servo Motor
Static Torque Mass Max Power Consumption Accuracy
LV341 Stepper Motor 550 oz-in 3.85 lb 250 W 350 steps/rev
BE232D Servo Motor 476 oz-in 3.1 lb 190 W NA
DM1004B Direct Drive Motor 566 oz-in 6.6 lb 300 W 1,024,000 steps/rev
18Motor Mounting Designs
- Stepper/Servo Motor Mounting
- Motor does not support axial loads
- Structure must be supported by test bed
- Direct Drive Motor Mounting
- Motor supports axial loads
- Structure can be mounted directly to motor
For bearing options, see slide 49
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20Structural Design
Option 1
Option 2
Option 3
- Requirement
- Bending lt 6 microns (pixel smear req.)
- Bending lt 0.3 (pixel smear req.)
- Stiffness of structure
Judgment criteria Lest mass, Moment of inertia,
Deflection
21Structural design Sunshade
- Requirements
- 12 Field of View
- Shade lens from direct sunlight
Total Height 17 cm
Inner diameter 7cm
Outer diameter 8cm
Height from support plates 5 cm
Sunshade opening 6 cm
Sun shade thickness 0.5 cm
Support plate thickness 1cm
22Structure design deflection requirement
feasibility
Approximation cantilever beam
- Requirement
- Bending lt 6 microns (pixel smear req.)
- Bending lt 0.3 (pixel smear req.)
- Stiffness of structure
Meets Requirement
Fails Requirement!
Solution substitution of support rods with truss
structure
For more detail, see slide 50
23Structural design Material selection
Design to goal Highest Mass/Stiffness
Mass/Stiffness
AISI 4130 Steel 9.562E-06
Aluminum 1350-H16 9.770E-06
Aluminum 2024-T3 9.434E-06
Aluminum 5182-O 9.475E-06
Aluminum 6061-T6 9.750E-06
Aluminum 7075-T6 9.808E-06
Titanium 6-4 9.697E-06
- Other Considerations
- Availability
- Cost
- Fatigue Strength
- Coefficient of thermal expansion
- Good Selections
- Aluminum 2024-T3
- Aluminum 5182-O
- Steel 4130
For more detail on material selection, see slide
51
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25Sensors
- Encoder option preferred over Resolver
- Low speed operations
- Accuracy
- Minimal Complexity
- Cost
- Ability to Modify
- Motors/Sensor package
- Availability
- Absolute Position
- Encoders can measure angular position and
velocity - Tachometer or Rate Gyro may be used in
conjunction with Encoder
- Accelerometers will be used to measure the
vibrations
For more detail on electronics, see slides 52,
53, 54
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27Simulation and Software Algorithms
Dynamics (calculate angular rate)
Kinematics (calculate angular position)
28Test Set Up
- Verification
- ?De-rotated ?Rotated
- ractualrdesired
- LflightLmodel
- Validation
- Image analysis
For more detail on controls, see slide 57, 58
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30Power
- Design Criteria
- Complexity
- Cost
- Mass
- Volume
- Possible Solutions
- Slip Rings
- Mercotac Rotary Electrical Connectors
- Conductix R Series Slip Rings
- Moog 6300 Series Slip Rings
- Batteries
- Nickel Cadmium
- Nickel Metal Hydride
- Lithium Ion
- Slip Ring/Battery Combination
For more detail on power, see slide 55, 56
31Work Breakdown Structure
DIABLO
Systems Engineer
Rotation Matt Sandoval Jason Gabbert
Structures Tim Sullivan Laura Fisher Lang Kenney
Optics Jason Gabbert
Management Laura Fisher
Controls Lisa Hewitt Tim Sullivan Nick Pulaski
Verification Nicole Demandante
Power Nick Pulaski
Scheduling
Camera Selection
Imaging Platform Design
Rotation Design
Identify Power Needs
Identify Verification Needs
Software Diagrams
Task Management
Testbed Sizing
Motor Selection
Hardware Selection
Hardware Selection
Test Set Up
Sunshade Design
Group Management
Define Pixel Smear
Bearing Selection
Data Acquisition and signal conditioning
Testbed Simulation
Testbed Design
Risk Management
Geometry Design
Integration with Sensors
CAD Model
Software Algorithm
FEM analysis
Final Testing
Fabrication
32Schedule through CDR
For rest of detailed schedule, see slide 59
33Schedule for Spring Semester
More detailed schedule, see slide 61
34Cost Estimates
Team Component Unit Cost Quantity Approx Cost Margin Total Cost
Optics Camera 500 1 500 20 600
Mirror 50 1 50 25 62.50
Mirror Mount 100 1 100 25 125
Electronics and Sensors Encoders 50 2 100 25 125
Rate Gyro/Tachometer 50 2 100 25 125
Accelerometer 12 2 24 20 28.80
Miscellaneous 100 1 100 25 125
Rotation Motor 600 1 600 20 720
Drive 1,500 1 1,500 20 1,800
Controller 1,000 1 1,000 20 1,200
Testbed Motor 200 1 200 20 240
Bearings 150 2 300 20 360
Power Slip Rings 85 2 170 25 212.50
Batteries 20 1 20 15 23
Miscellaneous 30 1 30 15 34.50
Structures Bulk Material 150 1 150 20 180
4,944 5,961
35Mass Estimates
Mass kg
sun shade 0.437
Periscope 15
Test Bed 6.09
4 Support Rods 7.09
1 Support Plate 0.574
Camera 0.5
Motors 7.5
Electronics/Sensors 0.3
Power system 0.5
Total Rotating 23.401
Total Test bed 37.99
Total with 25 margin 47.49
36Risk Matrix
Inaccurate Sensors Motor does not work as specified Underestimate Vibration Behind in scheduling Over budget
Parts are delayed Fabrication error
Control software is inaccurate Compression in camera image
Mounting inaccuracy
Consequence
Probability
37Conclusion
- System design and subsystem design options will
fulfill customer requirements and expectations - System design is feasible within the budget,
time, and expertise level
Image FAST satellite artist sketch
http//sprg.ssl.berkeley.edu/fast/
38References
- Fundamentals of mechanical vibrations, S. Graham
Kelly, McGraw-Hill, Inc. - Engineering Mechanics Dynamics, Bedford/Fowler,
Prentice Hall, 2005 - http//www.mercotac.com/html/products.html
- http//www.conductix.com
- http//www.polysci.com
- http//www.onlybatteries.com
- http//www.panasonic.com/industrial/battery/oem/
- http//www.bbma.co.uk/batterytypes.htm
39BACKUP SLIDES
40Pros and ConsFixed Camera
- Pros
- Mechanically less complicated, no moving parts
- Control system not required
- Proven technology
- Cons
- Complete coverage would require 30 cameras with a
12 field of view. - For the given camera shutter speed (100ms),
resolution (1Meg), and field of view (12) and
assuming only a 1 pixel smear, the maximum
rotation rate would be 0.11718/s. Actual
rotation rate is 72/s.
Back to system level choice
41Pros and ConsPassive Stabilization
- Pros
- Simple design, easy to construct
- No de-spun motor required
- Aligns camera with magnetic field lines without
help from main satellite - No control loop needed
- Cons
- Difficulty with verification
- Potential interference with the science hardware
- Possible pointing and stability issues
- Cant point camera off of magnetic field lines if
desired
Back to system level choice
42Passive Stabilization Calculations
- Assuming that the de-rotated section is a solid
cylinder of radius R15cm with mass m0.5kg the
moment of inertia I is - If we want to be able to accelerate the despun
portion to an angular velocity ? of 72 degrees/s
(the speed of the satellite) within 1 second in a
frictionless environment, the required torque t
will be - To get the desired torque with a magnetic field
strength of B20,000 nT (the field strength from
orbit) the magnet must have a linear dipole
moment µ of - Using the magnetic torquers found at
http//www.smad.com/analysis/torquers.pdf a
torque rod which can generate a linear dipole
moment of 80 Am2 has a length of 0.5m, 2 coils,
and draws 4.7W of power at 28V. This gives a
turn density n and current i of - At the center of a long solenoid the magnetic
field strength Bµni where µµ0k. The relative
permeability of a nickel alloy for the core is
about k8000, so the field strength generated by
this magnet is
Back to system level choice
43Rail Car Calcuations
- Pros
- A small movement in the motor will not result in
a large deviation in pointing accuracy - Not as stringent requirements on motor
sensitivity as other suggested designs. - Cons
- Thermal expansion would cause large errors
- Radius could expand by up to 5 (depends on
material) - Momentum balancing requirements would require
additional masses and precise balancing - Scaling with actual satellite would not be a
feasible size, requiring an unreasonably large
track - Changing moment of inertia would result in
scaling issue for the control loop - Electrical system very complicated and expensive
would require large slip ring
Back to system level choice
44Parallel Plate Calculations
- Pros
- Simple construction
- Cons
- Masses not evenly balanced would create
precession in the top plate. - Requires the addition of excess mass
- May not be able to meet the sun shading
requirement - Scaling
Back to system level choice
45Optical and Spin Axis Allignment Calculations
- Pros
- Easiest to balance mass
- Lots of space and flexibility in mounting camera
- Smallest amount of mass (lack of ballast)
- Less susceptible to thermal expansion issues
- Scalable to actual flight instrument
- Cons
- Complicated attachment to testbed
- Stability issues
- Jitter, vibration
Back to system level choice
46CameraLevel 1 Trade Study
Ease of Alignment (7) Cost (31) Features (17) Required Skill (24) Adjustability (21) Total
Component Level 1 1 1 1 1 29
Single Lens Reflect (SLR) 3 1.5 2 2 3 61.5
Point and Shoot (PS) 2.5 3 3 3 2 80
Features Zoom, Wireless, Timers Adjustability
Shutter, Aperture, Flash
Samples
Back to optics
47Rotation
- Test Bed Motor
- Simulates the rotation of spinning satellite
- Does not require precise control
- No size, weight or power constraints
- Options
- AC or DC motor
- Inexpensive
- Single voltage input
- Simple manual control
48Bearing Options
- Thrust Ball Bearings Ball
Bearings Cylindrical Roller
Tapered Roller - Bearings
Bearings
Radial Load Support Axial Load Support
Thrust Bearings No Yes
Ball Bearings Yes No
Roller Bearings Yes No
Tapered Bearings Yes Yes
Back to rotation
49Structural design
S/C Configuration
L
F mr?²
Modeled As Cant. Beam
?
v
m ¼ Total System Mass
Back to structure
50Material Selection
Feasibility Matrix Material density (lb/in³) 0.7 Modulus of Elasticity (ksi) 0.7 CTE, linear 250 (µin/in-F) 0.3
AISI 4130 Steel 0.284 0.7 0.337 29700 0.7 1 7 0.3 0.331
Aluminium 1350-H16 0.0977 0.7 0.979 10000 0.7 0.336 14.2 0.3 0.163
Aluminum 2024-T3 0.1 0.7 0.957 10600 0.7 0.356 13.7 0.3 0.169
Aluminium 5182-O 0.0957 0.7 1 10100 0.7 0.340 14.4 0.3 0.16
Aluminium 6061-T4 0.0975 0.7 0.982 10000 0.7 0.336 14 0.3 0.166
Aluminium 7075-T6 0.102 0.7 0.938 10400 0.7 0.350 14 0.3 0.1658
Titanium 6-4 0.16 0.7 0.598 16500 0.7 0.55 5.11 0.3 0.45
Invar 36 0.291 0.7 0.3298 20500 0.7 0.69 2.32 0.3 1
Shear Strength 0.8 Cost 0.9 Fatigue Strength (psi) 0.9 Total
130,000 0.8 1 13.48 0.9 0.353 0.9 0 2.153113
11000 0.8 0.084 11.25 0.9 0.423 0.9 0 1.418867
41000 0.8 0.315 12.53 0.9 0.379 20000 0.9 0.862 2.340604
21800 0.8 0.167 4.76 0.9 1 20000 0.9 0.862 2.796396
24000 0.8 0.184 5.91 0.9 0.8054 14000 0.9 0.603 2.38815
48000 0.8 0.369 11.37 0.9 0.4186 23000 0.9 0.991 2.516004
79800 0.8 0.613 41.25 0.9 0.115 23200 0.9 1 2.438711
0.8 0 59.93 0.9 0.079 0.9 0 1.084855
AISI 4130 Steel
Aluminium 1350-H16
Aluminum 2024-T3
Aluminium 5182-O
Aluminium 6061-T4
Aluminium 7075-T6
Titanium 6-4
Invar 36
Back to materials
51Electronic Requirements on Angular Position and
Angular Velocity
- Requirement from Optics
- Maximum of 6 pixels smeared per line
- 1595 pixels in 12 field of view 0.0075 /pixel
- 6 pixels 0.045
- Shutter Speed 0.1 sec
- Only can smear 0.045 per 0.1 sec exposure
- Thus smear gt 0.451 /sec 0.075 rpm
Back to electronics
52Encoder and Resolver Matrix
Encoder Resolver Total
Low speed operations
Accuracy
Minimal Complexity
Cost
Modification
Motors/Sensor package
Availability
Absolute Position
Back to electronics
53Electronic Requirements on Vibrations
- Resolution
- a ? x (? x r)
- ? 1/3 rev/sec 2.09 rad/sec
- r 6.13 cm
- a 26.79 cm/s2
- Acceleration 27.3 mg gt resolution is 27.3 mg
- Bandwidth
- Shutter speed 0.1 sec
- Frequency due to camera 10 Hz
- f 1 kHz
Back to electronics
54Power
Slip Rings Size (in3) Weight Cost
Mercotac 2.6 4 oz 170
Conductix 71 10 lbs 700
Polysci 4.3 8 oz 440
Batteries
NiCd 0.65 1 oz 5
total w/ motor 84.5 8.6 lbs 690
total w/o motor 5.2 8 oz 40
NiMH 0.65 1 oz 6
total w/ motor 84.5 8.6 lbs 828
total w/o motor 5.2 8 oz 48
Li-Ion 1.5 1.5 oz 15
total w/ motor 69 4.3 lbs 690
total w/o motor 4.5 4.5 oz 45
Back to power
55Batteries and Slip Rings
Cost Complexity Mass Size
Mercotac SR 8 7 9 10
Conductix SR 4 7 3 5
Moog SR 6 7 9 10
NiCd 4 8 5 4
NiMH 3 8 5 4
Li-Ion 4 8 7 5
Combination 10 6 8 8
Back to power
56Functional Block Diagram
- Torques
- Environmental (E1 E2)- drag
- Friction (F1 F2)
- Spinning Platform Motor (M2)
- Applied Torques
- De-rotated Platform Motor (M1)
- Equations of Motion
Back to controls
57Microcontroller
- Input position and velocity sensor data
- Output signal to de-rotating motor
- Process PID or PI control law
Back to controls
58Schedule
Back to fall schedule
59Schedule
Back to fall schedule
60Schedule for Spring Semester
Back to spring schedule
61Schedule for Spring Semester
Back to spring schedule