Post on 09-Feb-2016
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Camera Protection using Sun Sensor-Shutter Device
22-July 2008Jay Jiaquan Zheng
Mentor: Dennis Douglas
Overview of Sun Sensor – Shutter Device
• Analogy: Human Eye & Camera – Purpose Of Sun Sensor – Shutter Device
• Introduction of Sun Sensor – Shutter Device– System Diagram– Overall Preliminary Design
• Detailed Design of System– Sun Sensor– Electrical Components – Solar Shutter
• Summary & Path Forward
– Has design met specification– Future goals
The Human Eye Provides A Conceptual Basis For A Solar Sun Sensor
……There’s a reason they tell you not to look into the sun!
• Brain – Sun Sensor
• Eyelid – Solar Shutter
• Eye – Camera
Camera
Sun Sensor
Solar Shutter
• SS boresighted to telescope
• Shutter mounted on back of telescope
• Can be apply to ALL telescopes
Sun Sensor
SS Design:Extend/RetractableRay-Box, pinhole in front, optical detector in the back.
Shutter Design: Slider-Crank usingRack & Pinion assembly driven by a Micromotor.
Shutter
Preliminary Design Locates Sun Sensor & Shutter Device On A Telescope
TelescopeHousing
front
back
ADC (Analog Digital Converter)
Microprocessor
2
Overall System Diagram Links Functionalities Of COTS And Custom Components
Slider –Crank Mechanism
Motor
Convert to Mechanical Power (Torque)
Lid3
OPM Convert toElectrical Power (voltage)
OPD
Pinhole
1
Detector Optical Power Input (sun light)
COTS = Commercial Off The Shelf Components
SolidWorks Modeling Suggests Sun Sensor (Ray-Box) Design Meets Specifications
• Housing
– Adjustable : Threshold: 10o – 60o
– Determine by: Distance: Detector – Pinhole
• Complete CAD Assembly Constructed in SolidWorks
Back Mount
Detector Housing
Pinhole Extender
Thread pattern
Ray-Box Geometry Allows For Multiple Solar Exclusion Angles To Be Set
L
θ
R
r
a b ( )tan
R rL θ
θ+
=
Geometric Relationship:
θ
Sun Position 1
Sun Position 2
L
R
r
detector
pinhole
Adjusting Length Of Sun Sensor Corresponds To Specific Solar Threshold Angle
6.702 / (tan )L θ=
Detector Radius,
R : 5.207 mm
Pinhole Radius,
r : 1.500 mm
θ (o) l (mm) θ (o) l (mm)
10 76.581 36 20.620
12 63.746 38 19.458
14 54.567 40 18.408
16 47.673 42 17.454
18 42.302 44 16.583
20 37.998 46 15.784
22 34.469 48 15.048
24 31.521 50 14.368
26 29.021 52 13.737
28 26.872 54 13.149
30 25.005 56 12.601
32 23.366 58 12.087
34 21.915 60 11.605
Threshold Angle- Given by Optical Straylight Analysis -Cameras can be damage when reached
Detecting Threshold Angle Using Voltage
Curve Generated By Optical Power Meter Red area represents •Threshold Angle = Solar Exclusion Zone
OPM
detector
Vo
ltag
e re
adin
g
Sun Positions
30o
0
25mm
Optical Power Meter outputs voltage depends on incident light
summer
winter
Computing Unit Analysis Signal From Sun Sensor Effectively Controls Shutter Device
• Analog to Digital Converter (ADC)– OPM outputs analog signals,
Microprocessor could only read digital signals.
• Microprocessor – Controls motion of motor in
Shutter device
SolidWorks Modeling Of Shutter Provides Spatial Tolerances & Structural Properties
Lid
Ball Slide
Motor
Rack & Pinion
Slider-Crank
If it takes 10 seconds for your eyelid to close when looking directly at the Sun…
Slider-Crank Mechanism
Synthesized based on Position, Velocity & Force/Stress Analysis.
Rack & Pinion Assembly
Designed using Dynamic Analysis.
Motor
Selected based on Max Torque.
Superimposing All Major Components Allows For Analysis Of Effective Shutter Design
Ball Slide
Selected based on sliding distance.
Position Analysis & Motion Of Slider-Crank Modeled Using Matlab Programming
Lid
slider
Velocity Analysis Of Slider-Crank Generates Relationship Between Lid And Slider Velocity
c sv v=r r
bcvr
o
b
c
bvr
1θφ
a
a lv v=r r
abvr
svr
fix
lvr
O
A
B
C
1/222
1 1 11
2sin sin sin sin cos( )
sin( )s
lAB AB
BC BC
vv θ φ θ φ φ θπ φ θ
⎡ ⎤⎛ ⎞= ⋅ + ⋅ − ⋅ ⋅ ⋅ +⎢ ⎥⎜ ⎟− − ⎝ ⎠⎢ ⎥⎣ ⎦
Note: All terms defined in Position Analysis except slider velocity , or vs .
( )lid slider f positionv v= ⋅
Velocity Polygon
Lid
Slider
Dynamic Analysis Performed On Rack & Pinion System Based On Kinetic Energy Theory
T – motor torque x – rack displacementR – gear radius I – gear inertia m – rack mass
•Equivalence Inertia
•Dynamics Model
2eI mR I= + R
I
x, vs
T
m2
2s
TRv x
mR I= ⋅
+
Customer Specification Designer Input
Calculation OutputPurchase Parts
LinkageFactor Safety
Response Time
MaximumAllowable Pressure
Slider Acceleration
Slider Velocity
Lid Velocity
Motor
Slide
Gears
Dimension
Position
Materialn Lg
P
T
R,I
a
dvs
(x,y,z)
vl
Customer
$
Block Diagram Demonstrates Design Process And Components Specifications of Shutter Device
GUI Interface Allows User Input To Optimize Design Based On System Parameters and Variables
Summary and Path Forward
• Effective Sun Sensor-Shutter Device can be constructed using Commercial Off The Shelf and custom components.
• Modeling suggests this device will have a time response of 0.4 seconds and perform safely.
• Future goal is to determine costs of COTS and custom equipments and integration plan...
Acknowledgement Dennis Douglas,
Daron Nishimoto, Riki Maeda, Chet Jonston
Lani LeBron, Scott Seagroves,
Lynne Raschke, Lisa Hunter
The Akamai Internship Program is funded by the Center for Adaptive Optics through its National Science Foundation Science and Technology Center grant (#AST-987683) and by grants to the Akamai Workforce Initiative from the National Science Foundation and Air Force Office of Scientific Research (both administered by NSF, #AST-0710699) and from the University of Hawaii.