Test-based Dynamic Characterizing of a Complete Truck by Operational Modal Analysis

At the end of its development cycle, a new truck variant is exposed to vibration tests, both in laboratory conditions by means of a 4-shaker test rig and in real road tests on a proving ground. The idea is to extend the use of these test data by applying Operational Modal Analysis and by being able to correlate the analysis results with Finite Element predictions. Basically, the only feasible way to perform a modal analysis experiment on a complete truck is by using test rig or real road excitation. In both cases the forces introduced in the structure are not available or difficult to measure and, hence, Operational Modal Analysis needs to be applied. To verify the effectiveness of Operational Modal Analysis using test rig data, it was decided to perform time-domain simulations using the complete vehicle model which was subjected to the same excitation as a real truck on the test rig. This paper will compare the directly computed Finite Element modes, the modes found by applying Operational Modal Analysis to the simulated time histories and the modes identified from the real test rig measurements.