Shapes Module

In the Shapes module, the mode shapes and residuals are computed. Information about the FRF dataset, references and responses sieve, and polyreference model orders is displayed in the Shapes Info panel. Hovering the mouse pointer over AFU Name will show some additional information about the data file or workspace imat_fn. Hovering the mouse pointer over References will show the references coordinate information. The START button at the bottom-right corner of the GUI starts the residues processing. AFPoly switches to the Verify module when completed.

Selecting a plotted line with the mouse pointer and holding down the middle button will highlight that line and its corresponding entry in the plot legend. Selecting a line in the plot legend with the mouse pointer and holding down the middle button will highlight that line and the corresponding line in the plot axes (this feature is not available in Matlab R2014b or later). The name from the legend will be displayed in the message line at the bottom of the window.

The mode shapes are estimated as the column of the residue matrix corresponding to the reference with the largest modal participation factor for each mode. If there is a driving point response, the residue can be scaled for unity modal mass (real shapes) or unity modal A (complex shapes). However, if there is not a driving point response, the shapes can not be scaled. In this case, the shapes are written as the computed residue for complex shapes. For real shapes, the residue is purely imaginary, but the shape is written as purely real for compatibility with finite element and correlation post-processing programs. The estimated residue can be reconstructed from the shape by multiplying it by j. If there is not a driving point response with which to scale a mode shape, the reference of the estimated residue is indicated in the ReferenceCoord field.

When computing real mode shapes, the estimated residues will be purely imaginary and the driving point residue should be negative. If it is, the mode shape will be purely real when scaled for unity modal mass. However, if the driving point residue is positive, the mode shape will be purely imaginary when scaled for unity modal mass. For compatibility with finite element and correlation post-processing programs, the modes shapes will always be written as real shapes, but the consequence of making an imaginary shape real is that the modal mass must be negative in order to correctly reconstruct the residue from the mode shape and modal scaling.

Poles List – The frequency and damping of the poles selected from the Stability Diagram in the Poles module are listed in the Poles List, which is the table in the lower left side of the module. The check boxes in the Poles List determine if a pole is enabled. Only the enabled (checked) poles are included in the residues processing, written to a file or the MATLAB workspace, or sent to the animator using the Send to Animation Tool. The Poles List has a context menu to check all or check none of the poles, or to reset edited poles to the as-computed values. The rows of the Poles List can be selected with the mouse. Clicking in the Poles List and pressing Ctrl+A will select the entire list. The Remove button will remove the selected poles from the Poles List. The Animate button will send the polyreference solver shapes of the selected poles to the animator, whether or not the pole is checked. If the Animate Back-Expanded Shapes check box is checked, then the shapes will be back-expanded when sent to the animator. There are pole markers (inverted triangles) at the top of the plot axes, which are filled if the corresponding pole is checked or empty if not.

Shapes Model : Method – Select the shapes solver method to either use the polyreference solver residues or to refit the residues for the checked poles in the Poles List. If the solver method is selected, then only the residuals are computed in the Shapes module.

Shapes Model : Type – Select the type of mode shapes that will be computed, either real (normal) or complex. If the Shapes Model Method is 'solver', then the Shapes Model Type can only be 'complex'. To compute real mode shapes, the residues must be refit.

Shapes Model : Residuals – Select the residual terms to include in the shapes model from the list of 'upper & lower', 'upper', 'lower', or 'none'.

Shapes Model : Refit Freq – Select the frequency range or band about each pole to be included in the refit residues processing. If 'range' is selected, the frequency range is set by the Lower and Upper Freq Range. If 'bandwidth' is selected, the spectral lines in a constant frequency bandwidth about each pole are included. If 'lines' is selected, the same number of spectral lines about each pole is included. If 'percent' is selected, the spectral lines in a frequency bandwidth that is a percent of the pole frequency about each pole as are included. The frequency bandwidth, number of spectral lines, or frequency percentage is set by the Shapes Model Refit Band.

Shapes Model : Refit Band – Enter the bandwidth, number of spectral lines, or percent of pole frequency for the refit residues processing. The entered value depends on Shapes Model Refit Freq. If 'bandwidth', it is entered as frequency in Hz. If 'lines', it is entered as number of spectral lines. If 'percent', it is entered as percentage of pole frequency. The value of the Refit Band applies to either side of pole frequency, that is, if the Refit Band is set to a 2 Hz bandwidth, then the spectral lines encompassed by ± 2 Hz about each pole are included.

Shapes Model : Refit Min Lines – Enter the minimum number of spectral lines to include for each pole in the refit residues processing if the Shapes Model Refit Freq is 'percent'. At low frequencies, the percentage of the pole frequency can be a very few number of spectral lines, possibly less than one. The Refit Min Lines sets the minimum number of spectral lines to include, even if the percentage of the pole frequency is more than that specified.

Freq Range : Lower & Upper Freq – Enter the lower and upper limits of the frequency range to be processed. These values can also be set using the two cursors in the plot axes. There is a context menu on the two edit boxes from which the frequency range can be set based on the minimum and maximum frequencies of the poles.

Plot Function – Select the mode indicator functions to plot. The available MIFs are the same as for the Setup and Poles modules.

Plot Function : CMIF Order – Select the ordering of the CMIF and QMIF functions. If the CMIF Order is 'sorted', the CMIF and QMIF functions are sorted by decreasing magnitude at each spectral line. When CMIF Order is 'tracked', the CMIF and QMIF functions are sorted based on the similarity of the left singular vectors between adjacent spectral lines. The left singular vectors are compared by determining the maximum inner product for the vectors from adjacent spectral lines. The singular values are sorted accordingly.

Plot Function : Max MIF Order – Select the maximum order of the mode indicator functions that are plotted.

Responses – If the Shapes Model Method is 'refit', select the responses to include in the sieve for residues processing. Use the context menu to select the list attributes, disable selected responses, enable all responses, sieve by coordinate trace, or open the Responses dialog. If the Shapes Model Method is solver', the sieve defined in Setup module defines the responses for the shapes.

Tools > Shapes > Send MIFS to UIPLOT – Computes (if necessary) and sends all MIFs to UIPLOT.

Tools > Shapes > Send MIFS to IMAT Plot – Computes (if necessary) and sends the selected MIF to an IMAT plot figure.

Tools > Shapes > Send MIFS to spVIEW MIFs – Computes (if necessary) and sends the selected MIFs to the spVIEW MIFs module. A list dialog is presented from which to select the MIFs to send. If spVIEW is already running, the functions are sent to this instance of spVIEW, otherwise a new spVIEW is started.