Visual Modal ProTM

VT-550

Credit: KSC

The Visual Modal Pro™ package combines the features of the Visual Modal™ package with the features of the VES-4600 Advanced Modal Analysis option.

The Advanced Modal Analysis option includes advanced Multiple Reference curve fitting methods for extracting the modal parameters of closely coupled modes or repeated roots from multiple reference FRF data. This option also includes Stability diagram methods for finding modes in data where two or more modes are represented by a single resonance peak on a Mode Indicator curve.

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VT-550 Visual Modal Pro™also includes Operational Modal Analysis tools. For cases where the excitation forces cannot be measured and output-only responses are acquired, modal parameters can still be extracted from a set of specially processed Cross Spectra or ODS-FRFs, thus providing a complete set of tools for extracting modal parameters from measurements made in any type of testing environment.

Modal parameter estimation (curve fitting) is done in three steps:

  1. Count the number of modes using a Mode Indicator function
  2. Estimate the modal frequency & damping for each mode
  3. Estimate a modal residue (a mode shape component) for each mode & each measurement.

Visual Modal ProTM Features

  • Mode counting to identify closely coupled modes & repeated roots using either a Multi-Reference Complex Mode Indicator Function (Multi-Ref CMIF), or a Multi-Reference Multivariate Mode Indicator Function (Multi-Ref MMIF)
  • Curve fitting using the Multi-Ref Orthogonal Polynomial method
  • Multi-Ref Quick Fit. Automatically executes three curve fitting steps (count modes, estimate frequency & damping for each mode, estimate residues for each mode) with minimal user interaction
  • Multi-Reference curve fitting using either the Z-Polynomial, the Complex Exponential, or the Alias-Free Polynomial (AF Poly) curve fitting method to estimate stable groups of modal frequency & damping (stable pole groups). All poles are displayed on a Stability diagram.
  • Stability diagram. A graphical display of frequency & damping estimates (poles) in differently colored stable pole groups. All poles are calculated using curve fitting model sizes ranging from 1 to a user-defined maximum model size
  • Stable Poles diagram. A graphical display of poles (frequency & damping estimates) in differently colored stable pole groups
  • Stable Poles Group. A group of poles on a Stability or Poles diagram that satisfy a user-defined minimum number of poles that lie within user-defined frequency & damping tolerances
  • Shape Complexity Plot. A graphical display of the complex shape components of one or more mode shapes
  • Shape Magnitude Ranking. A graphical display of the ordered magnitudes of the shape components of each mode shape
  • Shape Expansion.  A set of shapes with many DOFs is curve fit to one or more shapes with few DOFs, to create one or more new shapes with many DOFs in them
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  • Deconvolution window. When this window is applied to a set of Cross Spectra or ODS-FRFs, operational modal parameters can be extracted from them using FRF-based curve fitting methods
  • Modal Model from OMA modes. A modal model (a scaled set of mode shapes) can be created from a set of output-only operational mode shapes
  • Mode Indicators for counting modes. Either a Complex Mode Indicator Function (CMIF) or a Multivariate Mode Indicator Function (MMIF) can be calculated and displayed. All of the resonance peaks above a scrollable noise threshold are automatically counted
  • Frequency & damping curve fitting. Either the Local or the Global Orthogonal Polynomial method can be used, with extra polynomial terms to compensate for out-of-band modes
  • Residue curve fitting. Either the Orthogonal Polynomial method or the Peak Cursor method can be used
  • Quick Fit. With one command, all three curve fitting steps are executed with minimal user interaction
  • Frequency & damping estimates are graphically indicated on the Mode Indicator graph
  • A Curve Fit function is overlaid on each measurement to graphically confirm each curve fit
  • Selected measurements and frequency bands can be used to improve your modal parameter estimates
  • All curve fitting data is saved with each measurement
  • FRFs can be synthesized using the parameters of selected modes
  • Modal Assurance Criterion (MAC). A 3D bar chart or spreadsheet display of the MAC values between all mode shape pairs. If MAC = 1, two shapes are the same.  If MAC < 0.9 two shapes are different.
  • Shape Difference Indicator (SDI). A 3D bar chart or spreadsheet display of the SDI values between all mode shape pairs. If SDI = 1, two shapes have the same values. If SDI < 0.9 two shapes have different values
  • Modal Participation. A 3D bar chart or spreadsheet display of the Real part, Imaginary part, and Magnitude of the modal participation factors that result when a set of shapes is curve fit to another set of shapes.
  • Mode shapes can be re-scaled between Residue mode shapes and UMM mode shapes
  • Modal parameters can be imported & exported using the Universal File Format (UFF-

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