CA09 exercise · Validation and model-updating exercise

FRF Parameter Fitting and MAC/FRAC

Fit stiffness and damping from a synthetic frequency-response function, compute MAC/FRAC-style agreement measures and prepare a validation statement.

60–90 minLinked to Parameter Identification and ValidationDashboard progress enabled

Aim

Parameter identification and objective validation

This exercise turns the validation lecture into a practical workflow: identify an oscillator from FRF data, compute MAC for mode-shape comparison and write a short validation statement.

1

Distinguish the workflow steps

Verification asks whether the implementation solves the chosen equations correctly. Validation asks whether the model is adequate for the real problem and intended use. Parameter identification updates uncertain parameters using reference data.

Which statement best describes validation?

2

Compute a MAC check

For the synthetic vectors used in the MAC code, the similar mode has MAC ≈ 0.9987.

Python exercise

Run the FRF parameter fit

The code fits natural frequency and loss factor to a synthetic measured FRF magnitude.

Expected observation

The identified natural frequency should be close to 120 Hz and the loss factor close to 0.045.

Teaching note

The example uses synthetic data so students can focus on the inverse-modelling workflow.

Python exercise

Compute MAC for mode-shape comparison

The code computes a MAC value between a reference mode and two simulated candidates.

Expected observation

The similar vector should have a MAC close to 1, while the different vector should have a much lower MAC.

Teaching note

MAC is insensitive to global sign but sensitive to mode-shape mismatch.

Written submission

Validation statement

Write a validation conclusion

Write a short conclusion explaining whether the identified FRF model is acceptable and what independent check you would still perform.

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