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Simcenter Testlab: Matrix-Heatmap Display

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(view in My Videos)

 

With the release of Simcenter Testlab 18, a new display called a Matrix-Heatmap was introduced. The Matrix-Heatmap enables users to quickly find important or outlier data within a large set of data as shown in Figure 1.

 

Matrix_Heatmap.pngFigure 1: The Matrix-Heatmap display makes it easy to compare 225 direct and reciprocal FRF functions to find a point direction sign error as indicated by the red colored areas.

Despite the display name, the display works with any kind of data, not just thermal information. Any type of measurement, from vibration to sound, is distilled to a single key numeric value which is shown in a matrix of colored squares/rectangles for quick analysis.

 

For example, in Figure 2, a Matrix-Heatmap is displaying the average values of five different orders from a sound measurement. This is a 1x5 matrix of values. 

 

Simple_Heatmap.pngFigure 2: The Matrix-Heatmap shows that the 2nd order has the highest average amplitude of all the orders being compared.

It is easy to tell that the 2nd order has the highest average amplitude of all the orders. This display can be used with much larger sets of data in the same way to quickly locate the most important or key measurement.

 

This article gives further details about the features of the Matrix-Heatmap display and shows some examples of how it can be used to analyze data sets.

 

Matrix-Heatmap Display Features

 

There are five steps to using the Matrix-Heatmap display:

  • Open the display and add data
  • Choose which attributes to sort/parse the data on the horizontal (X) and vertical (Y) axes
  • Select the calculation used for evaluating the measurement
  • Optionally choose a smaller frequency or rpm range for the calculation
  • View key measurements in a detached display

The steps are explained below.

 

Open Display and Add Data

 

To use a Matrix-Heatmap display to analyze data, the display needs to be opened and the data of interest added to the display as shown in Figure 3.

 

AddDataHeatmap.pngFigure 3: Click on the Matrix-Heatmap icon and drag and drop data into the display.

1. Click on the Matrix-Heatmap icon to open the Matrix-Heatmap display.

2. Drag and drop the data to be analyzed into the Matrix-Heatmap.  Highlight the first and last measurement in the list while holding shift to drop all the measurements at once.

 

Choose Attributes to Sort/Parse Data

 

Next the data can be sorted by attributes on the X and Y axes shown on Figure 4.

 

Attribute_Heatmap.pngFigure 4: Right click on either the horizontal (X) or vertical (Y) axis to sort the data by attributes.

Right click on the X or Y axis and choose “Attribute”.  The data can be sorted by:

  • DOF Id – The measurement name, or Point Identification field, of the data, including the direction field.
  • Reference DOF Id – For measurements like a FRF or crosspower, the reference or input location.
  • TPA Path – If using data from a Transfer Path Analysis (TPA), the path name can be used to sort the data.
  • Section Value – Data attributes like order number, frequency section, overall level can be used.

After selecting the data attributes of interest, the calculation to be performed on each measurement to distill it to a single number as described in the next section.

 

Select Calculation

 

How will the values displayed in the Matrix-Heatmap be calculated? 

 

To change the calculation, right click on the color scale (right side of the display) and choose “Processing” as shown in Figure 5.

 

Calculation_Heatmap.pngFigure 5: Right click on the color scale on the right side of the display and choose “Processing” to select the calculation method.

By default, these methods work across the entire frequency or rpm range of an individual measurement:

  • Linear Complex Average – Calculates an average of the amplitude and phase values across the frequency or rpm range.
  • Linear Amplitude Average – Calculates a linear average of only the amplitudes across the frequency or rpm range. Example: Average = (3 + 4 + 2)/3 = 3.
  • RMS Average – Takes a RMS average of the amplitude values across the frequency/rpm range. Example: Average = SQRT((32 + 42 + 22)/3) = 3.11.
  • Band Coherence – Compares the crosspowers and autopowers of responses and inputs. A coherence value that varies between 0 and 1 is the output. 

Band_Coherence.png

 

  • FRAC – Frequency Response Assurance Criterion – Indicates how similar the shape and amplitude of a set of FRF measurements are by returning a value between 0 and 1. A value of one indicates the measurements are similar, a value of zero indicates they are not.

FRAC.png

 

  • PAC – Phase Assurance Criterion – Indicates if phase is the same between FRF measurements by returning a value between -1 and 1. A value of positive one indicates the measurements are the same phase, a value of negative one indicates they are out of phase.

PAC.png

 

Optionally Choose Frequency or RPM Range for Calculation

 

Cursors can be used to evaluate the measurements over a smaller frequency or rpm range. Right click (while holding CTRL key) on the 2D display at the top of the Matrix-Heatmap and choose “Add Cursor -> Range” as shown in Figure 6.

 

Range_Heatmap.pngFigure 6: Select a smaller frequency range for evaluation by right clicking on the 2D display at the top and selecting “Range”.

As the cursors are moved the colors in the Matrix-Heatmap display change to reflect the new frequency or rpm range.

 

View Key Measurements

 

Key measurements identified by the Matrix-Heatmap can be quickly viewed using a detached display and processing cursor as shown in Figure 7.

 

Detached.pngFigure 7: Open a detached display and then add a cross cursor on the Matrix-Heatmap Display.

Follow these three steps, as shown in the picture above, to prepare a detached display for viewing data from the Matrix-Heatmap display:

 

1. Click on the Detached Display icon in the upper right corner.

2. In the Detached Display, open a FrontBack display by clicking on the icon.

3. In the Matrix-Heatmap, right click and choose “Add Cursor -> Cross”. Position the cursor over the desired measurement.

 

The use the processing feature of the cursor to drop data into the detached display as shown in Figure 8.

 

Detached_Drop.pngFigure 8: Right click on the cross cursor, select “Processing…”, and drop the block in the detached display.

To view data in the detached display, perform the following two steps which are illustrated above:

 

4. Right click on the newly opened Cross Cursor. Choose “Processing…”. A Cursor Processing menu is opened.

5. From the Cursor Processing menu, drop the block into the detached display.

 

By moving the cross cursor around the Matrix-Heatmap, the underlying measurement function will display automatically.  Multiple cross cursors can be used to overlay data in the FrontBack display if desired.

 

Matrix-Heatmap Display Examples

 

This section contains several examples of how the Matrix-Heatmap can be used to analyze and understand data.

 

Order Data

 

Several different orders (2nd, 3rd, 4th, 5th, 6th) at several different locations were measured on a rotating piece of machinery.

 

Using a double cursor over a rpm range from 938 to 1559, the 2nd order on the front subframe is the highest amplitude as shown in Figure 9.

 

heatmap_orders_low.pngFigure 9: When selecting a lower rpm range, the highest amplitudes are found on the front subframe.

The red square indicates the measurement with the highest average amplitude, while the blue squares have the lowest average amplitude.

 

Selecting a higher rpm range, as shown in Figure 10, the highest average amplitude vibration is at different location.  Instead of the subframe, it is on the vehicle body.

 

heatmap_orders_high.pngFigure 10: When selecting a higher rpm range, the highest amplitudes are found on the body.

If the same data was overlaid in a 2D display, as shown in Figure 11, it might be a little harder to identify the key paths.

 

2D_Orders.pngFigure 11: When the same order data is overlaid in a 2D display, the results are a little harder to interpret.

Order data is not the only kind that can be analyzed using the Matrix-Heatmap display.  In the next example, Frequency Response Functions from a modal test are analyzed.

 

Frequency Response Function (FRF) Data from a Vehicle

 

A set of Frequency Response Functions (FRFs) collected on a vehicle are added to a heat map as shown in Figure 12.  There are 38 response locations and two references.

 

heatmap_FRFs.pngFigure 12: This Matrix-Heatmap display shows the highest response amplitudes on the points labelled “whel” due to the reference inputs.

It can be seen that the FRFs on the steering wheel (whel:23 through whel:27) of the vehicle have the highest levels relative to the other components (rails, body, doors, engine, etc).  The steering wheel might be the reason the operator experiences high levels of vibration during vehicle usage.

 

Phase Assurance Criterion (PAC) on Reciprocal FRF data

 

When performing a Transfer Path Analysis, the same set of FRFs are often collected both directly and reciprocally.

 

The two sets of FRF data can be checked for consistency using the Phase Assurance Criterion (PAC) function in the Matrix-Heatmap display.

 

Both sets of FRFs are loaded into the Matrix-Heatmap display.  If there is a phase difference, caused by labelling a measurement +Z instead of –Z for example, this will show as a red colored area in the heat map as shown in Figure 13.

 

Heatmap_Phase_Flip.pngFigure 13: The Matrix-Heatmap display finds 180 degree phase inconsistency between set of direct and reciprocal FRFs.

Rather than having to compare the measurements one at a time, the heat map identifies the error quickly.  This check could be performed immediately after the measurement is done to ensure that high quality FRFs have been acquired before de-instrumenting the test article.

 

By either editing the direction label or multiplying the measurement by a negative one, the error can rectified. 

 

Note: Acoustic reciprocal FRFs are often measured using a Q-Source exciter. 

 

Display Options

 

The colors of a Matrix-Heatmap display can be reversed, so that red is either the highest or the lowest value as shown in Figure 14

 

heatmap_inverse.pngFigure 14: Color Scale on Matrix-Heatmap can be reversed.

Right click on the color scale on the right hand side and select “Color Scale -> Inverse” to reverse the colors.

 

The Matrix-Heatmap display can be copied into Powerpoint and Word and used as an Active Picture.

 

Questions? Email scott.beebe@siemens.com or contact Siemens PLM GTAC support.  Also feel free to post a reply to this article.

 

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