Antoine
c930728b1c
- 3 studies: sensitivity (Method D), stiffness sweep (Method B), robustness - Atomizer specs with run matrices, Zernike annular OPD extractor - War-room validated hybrid B+D method
73 lines
2.6 KiB
Markdown
73 lines
2.6 KiB
Markdown
# GigaBIT M1 — Reference Frame Stiffness Characterization
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**Client:** StarSpec
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**Project:** P04-GigaBIT-M1
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**Created:** 2026-03-04
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**Status:** Active — Model Setup
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---
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## Objective
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Determine minimum stiffness requirements for StarSpec's reference frame at 5 mirror support interface points. Quantify WFE sensitivity to frame compliance so StarSpec can design their frame to spec.
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## Approach
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**Hybrid B+D method** (war-room validated):
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1. **Method D (Sensitivity):** Prescribed unit displacements at each unique interface point, extract Zernike WFE sensitivity coefficients (nm/μm per DOF per point)
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2. **Method B (Stiffness Sweep):** CBUSH spring-to-ground at 5 interface points, sweep K to find knee points
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3. **Robustness:** One-soft-point, combined compliance, correlated displacement tests
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## Key Numbers
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| Metric | Value |
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|--------|-------|
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| Baseline WFE @ 40° | ~7.0 nm RMS (J5+ filtered) |
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| Baseline WFE @ 60° | ~13.0 nm RMS (J5+ filtered) |
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| ΔWFE budget (frame) | ≤ 1.0 nm RMS |
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| System allocation | ≤ 22 nm RMS (contract) |
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| Mechanical target | < 14 nm RMS |
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| Total runs | ~42 |
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## Interface Points (5 total)
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| Label | Type | Symmetry |
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|-------|------|----------|
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| V_top | Vertical support | Unique (on Y-Z symmetry axis) |
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| V_left | Vertical support | = V_right mirrored |
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| V_right | Vertical support | = V_left mirrored |
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| L_left | Lateral support | = L_right mirrored |
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| L_right | Lateral support | = L_left mirrored |
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**Unique points to test:** 3 (V_top, V_side, L_side)
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## Model
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- **Solver:** NX Nastran SOL 101 (linear static)
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- **Coordinate system:** Global (Z = optical axis)
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- **Zernike extractor:** Annular OPD, 50 modes, J5+ filtered RMS
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- **Reference subcase:** 20° elevation
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- **Test subcases:** 40° and 60° elevation
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- **Inner radius:** 135.75 mm (central hole)
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- **Outer radius:** 500.0 mm
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## Project Structure
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```
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gigabit-m1-frame-stiffness/
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├── README.md ← You are here
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├── models/ # NX model files (drop .prt and .sim here)
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├── studies/
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│ ├── 01_sensitivity_method_d/ # Unit displacement sensitivity (9+3 runs)
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│ ├── 02_stiffness_sweep_method_b/ # K sweep campaigns (20 runs)
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│ └── 03_robustness/ # One-soft-point, combined, correlated (8 runs)
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├── deliverables/ # StarSpec requirement document (Rev A)
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├── kb/ # Knowledge base notes
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└── images/ # Plots, screenshots
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```
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## PKM Reference
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Full documentation: `obsidian-vault/2-Projects/P04-GigaBIT-M1/03-studies/Reference-Frame-Stiffness-Characterization/`
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