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Journal Article

Power Train Model Refinement Linked with Parameter Updating Through Nonlinear Optimization

In the virtual development process validated simulation models are requested to accurately predict power train vibration and comfort phenomena. Conclusions from refined parameter studies enable to avoid costly tests on rigs and on the road. Thereby, an appropriate modeling approach for specific phenomena has to be chosen to ensure high quality results. But then, parameters for characterizing the dynamic properties of components are often insufficient and have to be roughly estimated in this development stage. This results in a imprecise prediction of power train resonances and in a less conclusive understanding of the considered phenomena. Conclusions for improvements remain uncertain. This paper deals with the two different aspects of model refinement and parameter updating. First an existing power train model (predecessor power train) is analyzed whether the underlying modeling approach can reproduce the physical behavior of the power train dynamics adequately.
Technical Paper

On the Use of the Wave Based Technique for a Three-Dimensional Noise Radiation Analysis of Coupled Vibro-Acoustic Problems

Driven by both the ever more restrictive legal regulations on human exposure to noise and the growing customers' expectations regarding the functional performance of a product, the vibro-acoustic behaviour of the product have gained a significant importance over the last decades. At the same time, product development phase and costs have been reduced in order to comply with the nature of competitive market. To cope with those conflicting design targets, the computer aided engineering (CAE) became an essential part of the product design process. A broad class of engineering vibro-acoustic problems involves the mutual coupling interaction between the structure and fluid. In this type of problem, the back-coupling effects are no longer negligible and the problem has to be considered as a fully coupled system. The conventional state-of-the-art techniques adopt the element-based schemes, such as the finite (FEM), boundary (BEM) and infinite element method (I-FEM).
Journal Article

Improved Comfort Analysis and Drivability Assessment by the Use of an Extended Power Train Model for Automatic Transmissions

The new generation of automatic transmissions is characterized by a compact and highly efficient design. By the use of a higher overall gear ratio and lightweight components combined with optimal gear set concepts it is possible to improve significantly fuel consumption and driving dynamics. Precise and efficient real time models of the whole power train including models for complex subsystems like the automatic transmission are needed to combine real hardware with virtual models on XiL test rigs. Thereby it's possible to achieve a more efficient product development process optimized towards low development costs by less needed prototypes and shorter development times by pushing front loading in the process. In this paper a new real time model for automatic transmissions including approved models for the torque converter, the lock-up clutch and the torsional damper are introduced. At the current development stage the model can be used for comfort analysis and drivability assessment.
Technical Paper

Simulation of Engine's Structure Borne Noise Excitation due to the Timing Chain Drive

Due to durability and lifetime requirements, the timing drive systems of modern passenger car engines are often equipped with chain drives. Chain driven systems are usually more critical in view of NVH compared to synchronous belt-drives. Mainly the polygonal effect and the related phenomena, like impacts caused by the meshing between the chain-links and impacts in the engagement/disengagement regions of guides and sprockets, lead to an increased excitation of the engine's structure. Since the polygonal effect occurs with the meshing frequency, the excited vibrations are basically narrow banded and can finally be recognized as an annoying whine-noise. This paper describes the modeling (MBS) of the entire timing-drive system containing a bushing-chain-drive, camshafts and all connected single valve trains. The investigations carried out are mainly focused on the primary dynamics of the chain drive and the forces which are transferred to the engine's structure.
Technical Paper

A Methodology to Simulate Piston Secondary Movement under Lubricated Contact Conditions

The authors want to introduce a general methodology for the simulation of the dynamics of the piston-liner contact considering a realistic oil film at inner liner wall. Because of the complexity of this problem and in order to minimize computing time a twin model was developed. Firstly, a simplified model is used to compute piston motion trends and piston ring lubrication in minimum simulation time. Secondly a very detailed model simulating multi-body dynamics, surface vibrations and elasto-hydrodynamic contact is applied. Both, the theoretical background of the twin model and the advantages of the coupled simulation procedure given in the wide range of considerable influences are discussed. The result examples focus on interaction effects of piston secondary movement and the influence of the available oil film. Finally, the status of verification of the models using measured results is shown.
Technical Paper

Structure Borne Noise Prediction Techniques

The Noise Vibration Harshness (=NVH) behaviour of engines or power units is the one of the predominant factors for market acceptance of vehicles. To reach this goal it is necessary to reduce the absolute noise level and also the noise level in specific frequency ranges. In diesel engines the predominant noise or vibrations are caused by combustion. This excitation is transferred via the crank train and bearings to the outer noise radiating engine surfaces. For gasoline engines this transfer path is also important. In such engines noise is created in the area of the main bearings by vibrations of the crankshaft. In this paper a new prediction technique for the above mentioned vibration transfer problems which was developed at AVL during the last three years is described. The work was carried out in cooperation with AUDI AG and VW AG, West Germany.