Transcript Slide 1
Camera Protection using Sun Sensor-Shutter Device 22-July 2008 Jay 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 Sun Sensor • Brain – Sun Sensor • Eyelid – Solar Shutter • Eye – Camera Solar Shutter Camera ……There’s a reason they tell you not to look into the sun! Preliminary Design Locates Sun Sensor & Shutter Device On A Telescope Shutter Telescope Housing front Sun Sensor back SS Design: Shutter Design: Slider-Crank using Rack & Pinion assembly driven by a Micromotor. • SS boresighted to telescope • Shutter mounted on back of telescope • Can be apply to ALL telescopes Extend/Retractable Ray-Box, pinhole in front, optical detector in the back. Overall System Diagram Links Functionalities Of COTS And Custom Components Detector OPD Convert to Electrical Power (voltage) ADC (Analog Digital Converter) OPM Optical Power Input (sun light) Pinhole 1 Convert to Mechanical Power (Torque) Slider –Crank Mechanism Microprocessor 2 Motor COTS = Commercial Off The Shelf Components Lid 3 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 Sun Position 1 r pinhole L R θ Sun Position 2 detector Geometric Relationship: R θ a r b L Rr L( ) tan Adjusting Length Of Sun Sensor Corresponds To Specific Solar Threshold Angle Detector Radius, R : 5.207 mm Pinhole Radius, r : 1.500 mm L 6.702 / (tan ) Threshold Angle - Given by Optical Straylight Analysis -Cameras can be damage when reached 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 Detecting Threshold Angle Using Voltage Curve Generated By Optical Power Meter Red area represents •Threshold Angle = Solar Exclusion Zone OPM summer detector 25 mm Voltage reading 30o 0 Optical Power Meter outputs voltage depends on incident light winter Sun Positions 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 Motor Slider-Crank Rack & Pinion Ball Slide If it takes 10 seconds for your eyelid to close when looking directly at the Sun… Superimposing All Major Components Allows For Analysis Of Effective Shutter Design Slider-Crank Mechanism Rack & Pinion Assembly Designed using Dynamic Analysis. Synthesized based on Position, Velocity & Force/Stress Analysis. Motor Ball Slide Selected based on Max Torque. 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 Lid o A va vl vl 1 c vbc b C O vb B fix vc vs vab vs Velocity Polygon a Slider 1/2 2 AB 2 AB vl sin1 sin f ( position sin 1) sin cos( 1 ) lid slider sin( 1 ) BC BC vs v v 2 Note: All terms defined in Position Analysis except slider velocity , or vs . Dynamic Analysis Performed On Rack & Pinion System Based On Kinetic Energy Theory T – motor torque x – rack displacement R – gear radius I – gear inertia m – rack mass • Equivalence Inertia I Ie mR I 2 R • Dynamics Model 2TR vs x 2 mR I T x, vs m Block Diagram Demonstrates Design Process And Components Specifications of Shutter Device Dimension Linkage Factor Safety Maximum Allowable Pressure Material n Lg Motor P T Gears Position R,I $ Customer Slider Acceleration (x,y,z) a Response Time vl Lid Velocity vs Slider Velocity d Slide Purchase Parts Calculation Output Designer Input Customer Specification 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.