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Journal Article

Power Train Model Refinement Linked with Parameter Updating Through Nonlinear Optimization

2010-06-09
2010-01-1421
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

2011-05-17
2011-01-1713
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

2012-06-13
2012-01-1529
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.
Journal Article

Predicted Roughness Perception for Simulated Vehicle Interior Noise

2012-06-13
2012-01-1561
In the past the exterior and interior noise level of vehicles has been largely reduced to follow stricter legislation and due to the demand of the customers. As a consequence, the noise quality and no longer the noise level inside the vehicle plays a crucial role. For an economic development of new powertrains it is important to assess noise quality already in early development stages by the use of simulation. Recent progress in NVH simulation methods of powertrain and vehicle in time and frequency domain provides the basis to pre-calculated sound pressure signals at arbitrary positions in the car interior. Advanced simulation tools for elastic multi-body simulation and novel strategies to measure acoustical transfer paths are combined to achieve this goal. In order to evaluate the obtained sound impression a roughness prediction model has been developed. The proposed roughness model is a continuation of the model published by Hoeldrich and Pflueger.
Technical Paper

Power Train Model Characteristics for Vibration Analyses – Conflicting Demands in Off Line and HiL Environments

2009-05-19
2009-01-2072
High quality predicting of power train vibration behaviour is desired in the early design stage for efficient vehicle development. Conflicting demands arise, since precise, fast simulation models are required. High precision of the models will allow for the elimination of resonance phenomena for future products, thereby ensuring their comfort for the customers. Fast simulations are becoming increasingly important for linking test environments with virtual prototypes under development. This paper deals with different aspects in these conflicting demands for power train vibration models. First, the paper investigates real-time capable mechanical models and decided in favor of the object-oriented modeling approach “for requirements of Hardware in the Loop” (HiL). This paper takes a closer look at the advantages of the object-oriented approach, the model setup, its validation and the test results.
Technical Paper

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

2002-03-04
2002-01-0451
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

2001-03-05
2001-01-0565
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

1990-02-01
900019
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.
Technical Paper

Seat Belt Retractor Noise Test Correlation to 2DOF Shaker Test and Real Vehicle Comfort

2018-06-13
2018-01-1507
Seatbelt retractors as important part of modern safety systems are mounted in any automotive vehicle. Their internal locking mechanism is based on mechanically sensing elements. When the vehicle is run over rough road tracks, the retractor oscillates by spatial mode shapes and its interior components are subjected to vibrations in all 6 degrees of freedoms (DOF). Functional backlash of sensing elements cause impacts with neighbouring parts and leads to weak, but persistent rattle sound, being often rated acoustically annoying in the vehicle. Current acoustic retractor bench tests use exclusively uni-directional excitations. Therefore, a silent 2 DOF test bench is developed to investigate the effect of multi-dimensional excitation on retractor acoustics, combining two slip-tables, each driven independently by a shaker. Tests on this prototype test bench show, that cross coupling between the two perpendicular directions is less than 1%, allowing to control both directions independently.
Technical Paper

Prediction of Eigenfrequencies and Eigenmodes of Seatbelt Retractors in the Vehicle Environment, Supporting an Acoustically Optimal Retractor Integration by CAE

2018-06-13
2018-01-1543
From an acoustical point of view, the integration of seatbelt retractors in a vehicle is a real challenge that has to be met early in the vehicle development process. The buzz and rattle noise of seat belt retractors is a weak yet disturbing interior noise. Street irregularities excite the wheels and this excitation is transferred via the car body to the mounting location of the retractor. Ultimately, the inertia sensor of the locking mechanism is also excited. This excitation can be amplified by structural resonances and generate a characteristic impact noise. The objective of this paper is to describe a simulation method for an early development phase that predicts the noise-relevant low frequency local modes and consequently the contact of the retractor with the mounting panel of the car body via the finite element method.
Technical Paper

Experimental Rattle Source Characterisation Using Matrix Inversion on a Reception Plate

2020-09-30
2020-01-1541
Minimizing rattle noises is becoming increasingly important for hybrid and electrical vehicles as masking from the internal combustion engine is missing and in view of the functional requirements of the office-like interiors of next generation automated vehicles. Rattle shall therefore be considered in the design phase of component systems. One hurdle is the modelling of the excitation mechanisms and its experimental validation. In this work we focus on excitation by loose parts having functional clearances such as gear systems or ball sensors in safety belt retractors. These parts are excited by relatively large low frequency displacements such as road-induced movements of the car body or low order rigid body engine vibrations generating multiple impacts with broad band frequency content. Direct measurement of the impact forces is in many cases not possible.
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