5.3 Measurement execution: impact locations and shaker control card

Impact locations card

The Impact Locations card shows the impacts as defined in the Prepare module. When selecting an excitation point, the camera moves automatically to that point. In some cases (e.g. parts that block the view), this may be undesired; the camera can be locked by right-clicking in the 3D viewer and activating Lock view port.

The measurement execution can be fully controlled from a standard keyboard; see the table in 2.3 Keyboard commands for the key commands.

Shaker control card

If you are using a shaker for your measurement, you must:

1. Select the impact location where the shaker is attached.
2. Open the shaker control card.
3. Select the shaker profile from the dropdown.
4. Press the Play button.

Automatic Measurement Selection (AMS)

With the automatic measurement selection (AMS) DIRAC can automatically select the most similar measurements. Similarity is based on the coherence of every possible pair of measurements. This function can be activated after the measurement or used in live mode during testing.

AMS settings:

• Name: this defines the name of the preset, which is shown on the button itself.
• Hammer: this sets the preset to affect only measurements made with the defined hammer. By default, AMS operates on every hammer. Note: if high/low/band-pass filtering is active on a hammer (input source), these frequencies are respected as minimum and maximum frequencies for the similarity calculation.
• Frequency: this defines the frequency band in which the similarity is computed. The default value is the entire frequency range as specified in the DAQ wizard step 2.
• Similarity: this is a metric used by the AMS algorithm which defines how similar measurements need to be in order to be considered for selection, after the two best-matching have been selected. It is calculated considering all sensor channels present in the project.
• Amount of excitations: this metric sets the maximum amount of selected measurements per excitation. It can be left empty, in which case it does not impose a maximum amount.

AMS after a measurement

After a measurement, you can apply AMS to a single excitation point or to all of them.

To apply AMS to a single excitation, complete the next steps:

1. Select the excitation.
2. Click the AMS preset button.

To apply AMS to excitations in the project, complete the next steps:

1. Open the drop-down menu of the AMS preset.
2. Select Run for all.

AMS in live mode

When in live mode, the most similar measurements will be selected every time a new measurement is recorded.

To activate AMS in live mode:

1. Double-click the AMS preset button.
2. Continue measuring.

Creating and editing an AMS preset

You can create multiple AMS presets with different settings.

To create and edit a preset for the AMS, complete the next steps:

1. Click to create a new AMS preset.
2. Open the drop-down menu of the AMS preset.
3. Edit the settings.

Impact ordering and grouping

By default, the order of the excitations within the Impact Locations card are grouped by VP.  By clicking on the Ungroup button, the excitations are instead sorted by index number.  They can be again re-sorted by clicking on Group by VP.

A similar option is available for grouping of multiple input sources, if multiple are defined. The grouping button will show up and can be used to group the measurements.

Incorrect excitation location

If impact data is accidentally saved in the wrong excitation point, these can be moved over to the right excitation point using drag and drop. A context-menu action is also available. Note that if data already exists within the new excitation entry, the measurement name will be updated with the appended name of those data.

Star impacts

A star is shown next to each measurement, which can be toggled on/off by pressing S. This has no effect for any computation, but helps to memorize this measurement as the one-hit that was “spot on”, which you might want to use as a reference when seeking for similar measurements.

Delete (rejected) measurements

To preserve file size and general performance of DIRAC, it may be desired to delete all invalidated measurements after completion. To do so, right-click on the relevant category and click on the relevant option.