Parameter Study on a Fully Trimmed Body: Opening Distortion Fingerprint of a Finite Element Model imported to Multibody Dynamics through a Modal Neutral File Compared to Test Data

Abstract

A complete vehicle model in a multibody dynamics simulation is considered constituting a key enabler for virtual development within the automotive industry. In collaboration with Zeekr Technology Europe, a multibody dynamics model of a robot-taxi has been studied. The multibody dynamics model includes a so-called fully trimmed body of a finite element model through a so-called modal neutral file. In particular, the opening distortion fingerprint consisting of diagonals over body openings and cross-sections, has been used as a measure to evaluate how well the simulation model correlate to test data. The main topic of this master’s thesis has been to perform a parameter study in order to investigate what parameters affect the correlation. In addition to simulations, a literature review has been conducted in order to understand the impact from the parameters related to the modal neutral file. From the literature review, examples of component mode synthesis by Guyan and Craig- Bampton on a beam are presented. The examples illustrate that the definition of the interface between the finite element model and the rigid components as well as the modes included in the synthesis have an impact on how well eigenpairs can be represented. Additionally, a physical beam has been utilized in order to understand the impact from rigidbody motions in simulations and on test data. The physical beam example illustrates that the accelerometers used measure the gravity field when being rotated. These rotations must be taken into account for lower frequencies. The outcomes of the parameter study are that the diagonals over the side doors and the A-pillar section show a poor correlation to the test data, while the remaining diagonals show a similar fingerprint to the one obtained from the test data. Furthermore, none of the studied parameters has shown a significant impact on the fingerprint over the side doors. Nevertheless, the considered frequency range used to obtain the fingerprint has shown to impact the correlation over the side doors. However, all diagonals require further investigation for the fingerprint to be correlated. The further investigation may include a review of the simulation models, a study on combined parameter effects, studying animations of the eigenmodes, dive deeper into the component mode synthesis or review the parameter settings, in particular the frequency range, of the fingerprint.