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Development and validation of an absolute Frequency Scanning Interferometry (FSI) network 1 st PACMAN workshop, CERN, Geneva, Switzerland 3 rd February.

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Presentation on theme: "Development and validation of an absolute Frequency Scanning Interferometry (FSI) network 1 st PACMAN workshop, CERN, Geneva, Switzerland 3 rd February."— Presentation transcript:

1 Development and validation of an absolute Frequency Scanning Interferometry (FSI) network 1 st PACMAN workshop, CERN, Geneva, Switzerland 3 rd February 2015 Solomon William KAMUGASA

2 1 st PACMAN workshop, CERN, Geneva PACMAN metrology 1. Fiducialisation of components 2. Alignment of components on a common support Integrate these 2 steps CMM preferred (0.3µm + 1ppm) However… Measurement volume is limited It’s immobile Goal: Develop portable alternatives Cable of comparable accuracies Able to cope with larger measurement volumes One such alternative is FSI multilateration Pre-alignment in tunnel µm over 200m

3 1 st PACMAN workshop, CERN, Geneva Coordinate determination using distances only Multilateration Requires distances from at least 3 known points Distance-coordinate relationship is well known Self-calibration possible by increasing stations and targets Coordinate uncertainty dependent on distance uncertainty Z Y X

4 1 st PACMAN workshop, CERN, Geneva Distance measurement system Absolute Multiline by Etalon Absolute distance (FSI) Uncertainty 0.5µm/metre Traceable to SI metre Up to 100 distance measurements simultaneously

5 1 st PACMAN workshop, CERN, Geneva System adaptation Software Current software provides distance information Some upgrades have been done linking approximate coordinates with distances Prototype MATLAB application to convert AML output file to form readable by LGC++ Hardware Modification of fibre end to enable absolute distance measurement between two points. 1.Design of suitable housing 2.Development of calibration strategy to determine any offsets

6 1 st PACMAN workshop, CERN, Geneva N=2 glass sphere Unlimited viewing angle Lower return intensity SMR Limited viewing angle Greater return intensity Advantages of wide viewing angle Better geometry hence better precision Provides more options for system configuration Retroreflector options Requirements High precision machining of 0.5” and 1.5” spheres Potentially compatible with Micro-triangulation

7 1 st PACMAN workshop, CERN, Geneva ±1mm (3cm sphere) Lateral tolerance test Why important? Greater tolerance = easier channel alignment Ability to continue measuring even with slight misalignment

8 1 st PACMAN workshop, CERN, Geneva Impact of misalignment on distance Do we measure the same distance if slightly misaligned? We conducted simulations in MATLAB to find out. Assumptions: uniform refractive index of air = 1 uniform refractive index of glass = 2 1mm

9 1 st PACMAN workshop, CERN, Geneva Impact of misalignment on distance Effect of lateral misalignment on distance measured using a 0.5 inch sphere

10 1 st PACMAN workshop, CERN, Geneva Impact of misalignment on distance Effect of lateral misalignment on distance measured using a 1.5 inch sphere

11 1 st PACMAN workshop, CERN, Geneva Multilateration strategy Need to measure distances to several points from a single point Divergent beam Motorised rotating head Several channels on one mount

12 1 st PACMAN workshop, CERN, Geneva Several distances from one point Divergent beam Motorised mount Several channels one mount Single beam to several targets Limited measurement volume (diverging lens) Limited measurement range (laser power) Technical know-how (software and hardware) Single beam to several targets Careful calibration strategy Method to ‘teach’ instrument position of targets Maximum measurement range (20m) and volume Several beams in one mount to several targets Strategy used in ATLAS Design of suitable mount and support frame Careful calibration strategy Divergent beam for easy alignment

13 1 st PACMAN workshop, CERN, Geneva Stretched wire measurement Attempt to measure 0.1mm Cu-Be wire directly with FSI Noticeable increase in intensity Insufficient for measurement Maybe possible with thicker wire Or different lens Alternatives: 1. Mount tiny reflectors on wire 2. Include reflector in wire tensioning system (Both options likely to have an impact on other measurements) 3. Detect wire using WPS

14 1 st PACMAN workshop, CERN, Geneva Network simulations CERN’s LGC++ will be used to conduct simulations & to solve the 3D network Simulations will: 1.Compare various network configurations to help choose the best 2.Take into account existing constraints 3.Determine the optimum number of channels 4.Provide post adjustment statistics and outlier detection.

15 1 st PACMAN workshop, CERN, Geneva Inter-comparison and validation FSI multilateration Accuracy Reliability Robustness Micro-triangulation Inter-comparison Leitz CMM Validation

16 1 st PACMAN workshop, CERN, Geneva Integration on FPAB

17 1 st PACMAN workshop, CERN, Geneva Extrapolation & summary Ultimate aim: To develop a portable coordinate measuring system based on FSI multilateration for CLIC that can be extrapolated to other projects Summary: System modification Stretched wire measurement Multilateration strategy Tests, validation & extrapolation

18 Thank you for your attention!


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