Enhanced Power Unit NVH Simulation with MBD Solver AVL EXCITE 2005-24-016
Several models have been developed for specific applications to accurately represent the dynamics of IC engines with particular focus on NVH behavior. These models aim to investigate the speed irregularity of crankshaft, the vibration level of the engine block and the engine mount vibrations. The speed fluctuations of the crankshaft causes timing drive excitations and the well known gear rattle phenomena. Engine block vibrations can be used as a reference for the radiated noise. Lastly, engine mount vibrations directly contribute to the cabin noise.
With the reduction of engine noise, the gearbox noise becomes more audible. Therefore, it is necessary to extend the MBD (Multi Body Dynamic) model, used for vibration and acoustic analysis of the power unit, in the gearbox direction. In this paper a model is presented, which was developed in joint collaboration between Elasis S.C.p.A. and AVL List GmbH. This model can represent the dynamics of the whole engine including: crankshaft system, timing drive and gearbox.
The gear noise simulation model is included in the conventional MBD model to predict the main gear noise phenomena. This is done by considering variable mesh tooth stiffness and nonlinear damping in the backlash region for all gear pairs, including the final gear pair and differential.