fourier series filtering concepts
TRANSCRIPT
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Fitting, Filtering and Analysis:Fitting, Filtering and Analysis:
Feature Extraction in DimensionalFeature Extraction in Dimensional
Metrology ApplicationsMetrology Applications
Mark C. Malburg
International DimensionalInternational Dimensional
Workshop 2002Workshop 2002
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MetrologySolutions
www.digitalmetrology.com
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Inside the BoxInside the Box A cloud of data points.
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Inside the BoxInside the Box Fitting
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Inside the BoxInside the Box Filtering
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Thinking Outside the BoxThinking Outside the Box Do the current analysis methods
provide the information that you arelooking for?
Modeling of performance
Correlation with process controls
Failure analysis
???? Why measure in the first place?
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Why measure?Why measure?
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Fitting, Filtering & AnalysisFitting, Filtering & Analysis There are many tools at our disposal for
the better analysis of data!
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Fitting, Filtering & AnalysisFitting, Filtering & Analysis An overview of some of the tools
Applications
Getting the tools into my box
Goal:
Make you think differentlyabout what you are measuring.
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FittingFitting Not much has changed!
Depending on the geometry there are afew options:
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FittingFitting
Fitting alone
doesntaddress all of
the issues
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FilteringFiltering Filter-phobia
I dont want to corrupt my data I dont use filters; they hide things
I want to see the realsurface
The proper use of filtering:
Exploit the features of interest
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A Filtering ToolboxA Filtering Toolbox ISO/TC213 Advisory Group 9
GPS Extraction Techniques Linear Filters
Morphological Filters
Spline Filters Spline Wavelet Filters
Alternating Sequence Filters
Robust Filters
Technical Specifications are being produced
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An easier viewAn easier view
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Traditional FilteringTraditional Filtering Gaussian Filter
End regions are not valid!
2
1)(
=c
x
c
exs
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Improved Gaussian FilteringImproved Gaussian Filtering Spline-based Gaussian Filtering
Filtered data is available all the way to theends of the raw data set!
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Mechanical Filtering (by Math)Mechanical Filtering (by Math) Morphological Filters CLOSING
OPENING
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Powerful filteringPowerful filtering Robust Filters
These filters are insensitive to extremepoints.
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What makes these coolWhat makes these cool Gaussian Filter (sensitive to extremes)
Robust Filter (insensitive to extremes)
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DisclaimerDisclaimer It should be noted that the concept of
sampling is closely connected to theconcept of filtering (mechanical,electronic or mathematical).
There, I said it.
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AnalysisAnalysis Surface texture has been suffering for
many years with a condition known as:
The Parameter Rash
However, many other fields could
benefit from some additional numericaldescriptions.
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AnalysisAnalysis A single number doesnt always
describe the functionality of a surface orinterface.
Examples:
Peak to valley distance, RMS
Rates of change, slope
Bearing Ratio, volumetric analysis
Harmonic Content
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Application Example #1Application Example #1 The Cam Lobe
The underlying, loadcarrying geometry isof interest.
The orientation and
shape of thisunderlying surface isto be characterized.
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Sampling the Cam LobeSampling the Cam Lobe
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Analyzing the Cam LobeAnalyzing the Cam Lobe Simple fitting does
not yield functionalinformation.
The outlierinfluences the formand orientation.
Simple filteringcorrupts the
underlying shape
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Simple filtering isnt enough...Simple filtering isnt enough...
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Combined Fitting/FilteringCombined Fitting/Filtering Suppress the nominal geometry via
Least Squares fitting.
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Combined Fitting/FilteringCombined Fitting/Filtering Remove outliers or apply robust filtering
on the residuals.
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Combined Fitting/FilteringCombined Fitting/Filtering Re-apply the suppressed geometry and
analyze the resulting data.
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Application Example #2Application Example #2 A gasket interface.
A solid surface in contact with aconformable component.
Rigid Surface
Conformable Surface (e.g. gasket)
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Conformable InterfacesConformable Interfaces There is a strong sensitivity to localized
surface variations (curvatures). Typically these are middle wavelengths.
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Traditional FilteringTraditional Filtering Bandpass waviness analysis is
somewhat useful.
Roughness FormWaviness
Transmission
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Bandpass WavinessBandpass Waviness Traditional filtering is used to separate
the data into 3 domains.
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Bandpass WavinessBandpass Waviness The bandpass waviness approach does
not adequately model the interface. Its good, but not great.
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Combined Filtering & AnalysisCombined Filtering & Analysis A better approach is to combine robust
filtering with morphological filtering.
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Combined Filtering & AnalysisCombined Filtering & Analysis First a robust filter is applied.
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Combined Filtering & AnalysisCombined Filtering & Analysis Next a morphological closing filter is
applied to the waviness profile.
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Combined Filtering & AnalysisCombined Filtering & Analysis The resulting profiles represent
conformability and the resulting gaps.
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Combined Filtering & AnalysisCombined Filtering & Analysis The cutoff and closing radius can be
tuned to simulate gasket properties. The gap area (between the morphological
and robust filtered profiles) can be
calculated as a functional analysis.
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Combined Filtering & AnalysisCombined Filtering & Analysis Similar peak-to-valley values, but
different performance:
Gap area is key!
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Old dogs, new tricksOld dogs, new tricks
How can I use this stuffHow can I use this stuff
on my machine?on my machine?
Answer:SoftwareAdd-Ins(Helpers)
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Direct Hardware InterfacingDirect Hardware Interfacing Example: Analog to digital conversion of
analog probe signal Requires calibration and often requires
other control interfacing.
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Serial InterfacingSerial Interfacing Many instruments provide data output
via a serial (RS-232 or other) port.
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Software InterfacingSoftware Interfacing Some instrument software packages
provide an interface for externalapplications.
Spawning of external applications
Dynamic Data Exchange (DDE)
Object Linking and Embedding (OLE/COM)
DDE/OLE
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File Based InterfacingFile Based Interfacing The control software simply stores a file.
The add-in package monitors the file andloads it when changed.
1. Save
3. Auto-Load
2. Monitor
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Fitting, Filtering & AnalysisFitting, Filtering & AnalysisSummary:
Several analysis tools are available tobetter exploit the features of interest.
Choose wisely Grasshopper!
These tools can be applied to manyexisting measurement systems.
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Thank you!Thank you!
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