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NST PRIMARY MIRROR CELL: ANALYSIS AND SOLUTIONS

NST PRIMARY MIRROR CELL: ANALYSIS AND SOLUTIONS. BBSO, 02/05/2004. 1. PM Cell Subsystems / Components. Active Primary Mirror PM Cell Assembly Axial and Radial Actuators Load Cells Thermal sensors Entrance Aperture PM Cell Cover Air Knives and Cooling System. BBSO, 02/05/2004.

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NST PRIMARY MIRROR CELL: ANALYSIS AND SOLUTIONS

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  1. NST PRIMARY MIRROR CELL:ANALYSIS AND SOLUTIONS BBSO, 02/05/2004

  2. 1. PM Cell Subsystems / Components • Active Primary Mirror • PM Cell Assembly • Axial and Radial Actuators • Load Cells • Thermal sensors • Entrance Aperture • PM Cell Cover • Air Knives and Cooling System BBSO, 02/05/2004

  3. 2. Active Primary Mirror BBSO, 02/05/2004

  4. 3. PM Assembly Picture from Bill Duch’s report BBSO, 02/05/2004

  5. 4. Axial and Radial Actuators BBSO, 02/05/2004

  6. 5. Load Cells BBSO, 02/05/2004

  7. 6. Major Requirements • PM Surface Quality on short time scale; • Real-Time control system: WFS and Loads; • Mechanical stability (high resonance freq); • PM Surface Quality on long time scale; • Thermal/Position stability for PM Cell; • Mirror seeing (< 1 deg difference); • Dimensions (thickness < 620 mm); • Weight = 1275 kg (including PM); BBSO, 02/05/2004

  8. 7. Analysis of PM Cell BBSO, 02/05/2004

  9. 7.1. Some static/thermal issues • Connection axial/radial rods to pucks: ± 1 mm tolerance requires about a few tens kg transversal force for radial rod (TBD); • A thermal introduced forces between PM Cell and pucks; For ± 12C: • Radial forces produce deformation of the PM (TBD); • Axial forces’ PTV deformation is about 200 nm; BBSO, 02/05/2004

  10. An Axial (Radial) Rod deformation model BBSO, 02/05/2004

  11. 7.2. Resonant Frequencies • For 36 axial supports and ideal (without any deflection) PM Cell: First tone is 44.8 Hz; • PM cell has its first eigen tone about 66 Hz; • Combined (Real Cell and PM): First tone is less than 35 Hz, what is lower than the whole telescope requirement: 40 Hz. BBSO, 02/05/2004

  12. 7.2.1. Mirror & Cell 1st tone BBSO, 02/05/2004

  13. 7.2.2. PM & Cell Tip/Tilt 43 Hz BBSO, 02/05/ 2004

  14. 7.2.3. PM & Cell Shifts 56 Hz BBSO, 02/05/2004

  15. 7.2.4. Mirror & Cell 2nd Axial 92Hz BBSO, 02/05/2004

  16. 8. Proposed PM Cell Improvements • Static / Thermal Issues • Special Ball Joints with small backlash; • Resonant Frequencies • Three Hardpoints; • More rigid Platform; • Dimensions BBSO, 02/05/2004

  17. 8.1. Ball JointsSpherical plain bearing designs (in USA 1-888-753-2000)http://www.skf.com/portal/skf/home/products/ BBSO, 02/05/2004

  18. 8.2. Three Hard points Three types of hard points were analyzed: • Three standard axial actuators with 100 lb Load Cell (proposed in “old” design); • Using “harder” Load Cells (1,500 lb instead of 100 lb) at three locations of axial supports; • Using three real hard points (no motion in axial direction). BBSO, 02/05/2004

  19. “Harder” Load Cells: Mode 1,2 (shifts) 56 Hz, 3,4(tip/tilt) 63 Hz, 5 (axial) 69 Hz BBSO, 02/05/2004

  20. Real Hard Points:Modes: 1,2 (shifts) 56 Hz, 3 (torsional) 113 Hz, 4,5 (tip/tilt) 180 Hz, 6 (first axial) 283 Hz BBSO, 02/05/2004

  21. 8.3. More Rigid Platform BBSO, 02/05/2004

  22. 8.4. PM Resonances vs hard points • PM on standard 36 axial supports shows its first axial tone (mode 1) at 44.8 Hz; • PM on three “harder” points shows its first axial tone (mode 5) at 69 Hz; • PM on three hard points shows its first axial tone (mode 6) at 283 Hz. BBSO, 02/05/2004

  23. 8.5. PM & Cell Resonances • PM & Old Cell with 36 Load Cells (100 lb) showed 1st axial tone is less than 35 Hz; • PM & Old Cell with Load Cells (1500 lb) has axial resonant on 40 Hz; • PM & Old Cell with three real hard points has its first axial mode on 47 Hz; • PM & Modified Cell with three hard points showed first axial tone on 135 Hz. BBSO, 02/05/2004

  24. CONCLUSIONS • Static and dynamical analysis of the Proposed preliminary PM Cell Design showed that some of its assemblies/parts may be improved. • Improved design with three hard points and ribbed platform has axial resonance tone about 135 Hz compare to 35 Hz with “Old” platform and no hard points. BBSO, 02/05/2004

  25. ACKNOWLEDGEMENTS • This work has been supported in part by NASA grant NAG5-12782, NSF grant NSF-ATM-0086999 and AFOSR grant F49620-03-1-0271. • Designing of the PM cell was done by Doug Neill and Bill Duch III. • Analysis, modeling and suggestions for PM Cell improvements were prepared by Mansur Iliyasov and Alexey Zverev (Lavochkin Science-Production Associations, Moscow, Russia) and Leonid Didkovsky (BBSO). BBSO, 02/05/2004

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