1 Quality checks for test-based models

The quality checks in DIRAC give you immediate insights into the quality of your test-based model. By integrating these checks in your measurement routine, you recognize problems early, discuss them with your colleagues and discuss solutions without starting from scratch. This saves costs and gives you control over the quality of your test-based model.

First-time-right test-based modelling

We know that a good model is built upon good data, and good data relies on a well-designed setup. To ensure that your test-based model is of high quality, DIRAC offers various quality indicators for each level. This allows you to precisely detect where problems in your model come from.

Setup checks

The VP conditioning indicates if all degrees of freedom of the Virtual Points can be identified with the defined sensors and excitation points. This quality check can be quickly repeated whenever you make adaptations to the setup during the measurement campaign. ODS animations help to check if all sensor positions and all cable connections of the test bench setup match the definitions in DIRAC.

Signal checks

The matrix viewer provides an intuitive overview of the entire FRF matrix. In magnitude mode, it allows you to quickly spot overloads in your data. In coherence mode, it helps you to spot various problems from the measurement system to the sensors and recognize insufficiencies in the excitations. With the hammer merge you can further improve the signal quality of your test-based model.

Model checks

DIRAC gives you various quality indicators to ensure that the identified Virtual Points dynamics have the high quality needed for the post-processing steps. The response and force consistency inspect the measured data of the sensors and excitations, respectively, to check their positions and orientations as well as the rigidity requirement of the Virtual Point Transformation. With a quick switch from the measured data to the VP-transformed data you can verify the passivity of driving point FRFs and physical plausibility of reciprocal FRFs.

Integrating quality checks into the measurement routine

Using quality checks is always a good idea. But the real benefit comes in when you include all quality checks in your measurement routine, as you can then spot and resolve problems directly when they occur.

The first checks are done at the computer – before approaching the test bench. While preparing your test setup in DIRAC, you can verify the conditioning of each virtual point. This checks if your setup allows to identify every degree of freedom. When this is checked, you can start creating the physical setup at the test bench.

After everything has been prepared at the test bench, only measure some excitations (e.g., one in each direction). These few measurements allow you to make sure that your measurement equipment functions properly and that you have recreated the same setup at the test bench as defined in DIRAC. When this is checked, you can start measuring the excitations of the first virtual point.

After measuring all excitations of the first virtual point group, you can verify the signal quality and model quality with various indicators. This makes sure that the measured FRF are coherent and without overloads and that the positions of sensors and excitations are correct. When the dynamics of the VP-transformed FRF look plausible, you can move on to the next virtual point.

With a measurement routine with integrated quality checks, you will build up high-quality test-based models – virtual point by virtual point. So, once you have verified the last virtual point, you can confidently export your data and disassemble the test setup.

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