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2014-06-30
Technical Paper
2014-01-2041
Alexander Ulz, Alfred Rust, Bernhard Graf, Alois Sontacchi
Abstract Due to future directives of the European Union regarding fuel consumption and CO2 emissions the automotive industry is forced to develop new and unconventional technologies. These include for example stop-start-systems, cylinder deactivation or even reduction of the number of cylinders which however lead to unusual acoustical perceptions and customer complaints. Therefore, it is necessary to evaluate the sound character of engines with low numbers of cylinders (2 and 3 cylinders) and also the differences to the character of the more common 4-cylinder engines. Psychoacoustic parameters are used to describe and understand the differences. Based on the gained knowledge possible potentials for improvement can be derived in the future. The used data base consists of artificial head recordings of car interior noise according to defined driving conditions measured on the AVL test track.
2014-06-30
Journal Article
2014-01-2042
Jan Hendrik Elm, Jens Viehöfer, Jan-Welm Biermann
Abstract The automotive industry permanently enhances Downsizing concepts due to environmental commitments and energy consumption concerns. Even in the category of city- and supermini-cars, great efforts are made for the development of highly charged engines with small displacement. So far the main focus of these developments is set on the reduction of CO2 emissions and fuel consumption. However these are not the only aspects, which have to be fulfilled by the vehicle in order to meet the demands of the customers and to be successful in competition. The NVH characteristics of such Downsizing vehicles have to match a class-specific level, which can only be achieved by additional measures. Regarding this, a view of the dynamic behavior of the entire vehicle is required. At the Institut für Kraftfahrwesen Aachen (ika) the potential for reducing fuel consumption and CO2 emissions of a Downsizing concept is investigated using a city-car as reference.
2014-06-30
Technical Paper
2014-01-2043
Bryce Gardner, Tiago Macarios
Abstract Speech transmissibility is a critical factor in the design of public address systems for passenger cabins in trains, aircraft and coaches. Speech transmissibility is primarily affected by the direct field, early low order reflections, and late reflections (reverberation) of the source. The direct and low order reflections are affected by the relative location of speakers and seats as well as the acoustic properties of the reflecting walls. To properly capture these early reflections, measures of speech transmissibility typically require time domain information. However, another important factor for speech transmissibility is background noise due to broadband exterior sources such as a flow noise sources. The background noise is typically modeled with broadband steady state assumptions such as in statistical energy analysis (SEA). This works presents an efficient method for predicting speech transmissiblity by combining ray tracing with SEA.
2014-06-30
Technical Paper
2014-01-2044
Yong Che
Abstract As motor assembly of Battery Electric Vehicle (BEV) replaces engine system of Internal Combustion Engine (ICE) vehicle, interior structure-borne noise induced by road random excitation becomes more prominent under middle and high speed. The research is focused on central driving type BEV. In order to improve interior noise in middle and low frequency range, dynamic load of BEV body must be identified. Consequently the structural noise induced by road excitation is conducted. The limitations of common identification method for dynamic body load are analyzed. The applied several identification methods are proposed for deterministic dynamic load such as engine or motor. Random dynamic load generated by road excitation is different from deterministic dynamic load. The deterministic load identification method cannot be applied to the random load directly. An identification method of dynamic body load for BEV is presented based on power spectrum decomposition.
2014-06-30
Technical Paper
2014-01-2045
Hiromichi Tsuji, Satoshi Takabayashi, Eiji Takahashi, Hitoshi Murakami, Shinichi Maruyama
A finite element (FE) model of vibro-acoustic coupling analysis, such as a vehicle noise and vibration, is utilized for the improvement of the performance in the vehicle development phase. However, the accuracy of the analysis is not enough for substituting a prototype phase with a digital phase in the product development phases. Therefore, conducting the experiments with the prototype vehicle or the existed production vehicle is still very important for the performance evaluation and the model validation. The vehicle noise transfer function of the road noise performance cannot be evaluated with the existed excitation equipment, such as the 3 or 6 directional electromagnetic shaker. Therefore, this paper proposes new experimental method to measure the road noise vehicle transfer function. This method is based on the reciprocity between the tire contact patch and the driver's ear location.
2014-06-30
Technical Paper
2014-01-2047
Georg Eisele, Klaus Wolff, Jannis Hoppermanns, Peter Genender
Abstract Transfer path analysis is a powerful tool to support the vehicle NVH development. On the one hand it is a fast method to gain an overview of the complex interplay in the vehicle noise generation process. On the other hand it can be used to identify critical noise paths and vehicle components responsible for specific noise phenomena. FEV has developed several tools, which are adapted to the considered noise phenomena: Powertrain induced interior noise and vibration is analyzed by VINS (Vehicle Interior Noise Simulation), which allows the deduction of improvement measures fast enough for application in the accelerated vehicle development process. Further on vehicle/powertrain combinations not realized in hardware can be evaluated by virtual installation of the powertrain in the vehicle, which is especially interesting in the context of engine downsizing from four to three or six to four cylinders.
2014-06-30
Technical Paper
2014-01-2049
Hiromichi Tsuji, Kimihiko Nakano PhD
This paper presents new technique to estimate the projected operational forces, which is the operational forces with respect to the evaluation location, at the connections of the separated passive substructures with reciprocity. Since the transfer path analysis (TPA) is conducted with respect to the evaluation location, the forces for the substructures are, therefore, also required only to estimate the projected operational forces. In order to estimate the forces, the projected inertance matrix, which is the projection of the inertance matrix onto the subspace with respect to the evaluation location, is estimated without measuring it directly. The acceleration responses at the connections of the passive substructure are measured by the excitation at the evaluation location with the reciprocity. The technique decomposes the acceleration responses into the output and input element vectors on the subspace. With those vectors, the projected inertance matrix is constructed.
2014-06-30
Technical Paper
2014-01-2086
Roland Sottek, Bernd Philippen
Abstract In the engine development process, the ability to judge NVH comfort as early as possible is a great benefit. The prediction of engine noise on the basis of a prototype engine without the need to install it in a real car significantly speeds up the development process and leads to a cost reduction, as prototype modifications can be evaluated faster. Meaningful predictions of the perceived NVH comfort cannot be achieved just by comparing order levels, but require listening to an auralization of the engine noise at the driver's position. With the methods of Transfer Path Analysis and Synthesis (TPA/TPS) a prototype engine can be virtually installed in a car using test-bench data. The interior noise can be estimated by combining source signals containing near-field airborne noise radiation and mount forces with transfer functions describing the transmission to the target position in the cabin.
2014-06-30
Technical Paper
2014-01-2085
Ki-Sang Chae, Seung Hwan Lim, Ji Woo Yoo, Seok-Gil Hong
Abstract Dash panel is the most important path of structure-borne and air-borne interior noise for engine-driven vehicles. Reinforcements, which are added to dash panel, are mainly designed in order to suppress the structure-borne noise contribution from the dash panel. However, the effects of dash reinforcements do not seem clear in the viewpoint of air-borne noise. In this paper, the insulation performance of a dash structure with spot-welded reinforcements is studied through several STL (Sound Transmission Loss) tests and STL simulations. The results of this study could be utilized for increasing the sound insulation performance of vehicle body structure.
2014-06-30
Technical Paper
2014-01-2092
Giorgio Veronesi, Christopher Albert, Eugène Nijman, Jan Rejlek, Arnaud Bocquillet
Abstract In many application fields, such as automotive and aerospace, the full FE Biot model has been widely applied to vibro-acoustics problems involving poro-elastic materials in order to predict their structural and acoustic performance. The main drawback of this approach is however the large computational burden and the uncertainty of the input data (Biot parameters) that may lead to less accurate prediction. In order to overcome these disadvantages industry is asking for more efficient techniques. The vibro-acoustic behaviour of structures coupled with poroelastic trims and fluid cavities can be predicted by means of the Patch Transfer Function (PTF) approach. The PTF is a sub-structuring procedure that allows for coupling different sub-systems via impedance relations determined at their common interfaces. The coupling surfaces are discretised into elementary areas called patches.
2014-06-30
Technical Paper
2014-01-2091
Zoran Radmilovic, Josef Zehetner, Daniel Watzenig
Abstract Hybrid electric vehicles (HEVs) with a power-split system offer a variety of possibilities in reduction of CO2 emissions and fuel consumption. Power-split systems use a planetary gear sets to create a strong mechanical coupling between the internal combustion engine, the generator and the electric motor. This concept offers rather low oscillations and therefore passive damping components are not needed. Nevertheless, during acceleration or because of external disturbances, oscillations which are mostly influenced by the ICE, can still occur which leads to a drivability and performance downgrade. This paper proposes a design of an active damping control system which uses the electric motor to suppress those oscillations instead of handling them within the ICE control unit. The control algorithm is implemented as part of an existing hybrid controller without any additional hardware introduced.
2014-06-30
Technical Paper
2014-01-2090
Joël Perret-Liaudet, Alexandre Carbonelli, Emmanuel Rigaud, Brice Nelain, Pascal Bouvet, C. Jacques Vialonga
Abstract The main source of excitation in gearboxes is generated by the meshing process, which generates vibration transmitted to the casings through shafts and bearings. Casing vibration generates leads to acoustic radiation (whining noise). It is usually assumed that the transmission error and variation of the gear mesh stiffness are the dominant excitation mechanisms. These excitations result from tooth deflection and tooth micro-geometries (voluntary profile modifications and manufacturing errors). For real cases, the prediction of noise induced by the Static Transmission Error (STE) remains a difficult problem. In this work, an original calculation procedure is implemented by using a finite element method and taking into account the parametric excitations and their coupling (Spectral Iterative Method, developed by the Ecole Centrale de Lyon).
2014-06-30
Technical Paper
2014-01-2089
Mahdi Mohammadpour, Ramin Rahmani, Homer Rahnejat
Abstract This paper presents an investigation of Cylinder De-Activation (CDA) technology on the performance of big end bearings. A multi-physics approach is used in order to take into account more realistic dynamic loading effects on the tribological behavior. The power loss, minimum film thickness and maximum temperature of big end bearings have been calculated during maneuver pertaining to the New European Driving Cycle (NEDC). Results show that bearing efficiency runs contrary to efficiency gained through combustion and pumping losses. Under CDA mode, the power loss of big end bearings is more than the power loss under engine normal mode. The problem is predominant at higher engine speeds and higher Brake mean Effective Pressures (BMEP) in active cylinders. It is also observed that the minimum film thickness is reduced under the CDA mode. This can affect wear performance. In addition, same behavior is noted for the maximum temperature rise which is higher under CDA.
2014-06-30
Journal Article
2014-01-2095
Janko Slavic, Martin Cesnik, Miha Boltezar
Abstract Car components are exposed to the random/harmonic/impact excitation which can result in component failure due to vibration fatigue. The stress and strain loads do depend on local stress concentration effects and also on the global structural dynamics properties. Standardized fatigue testing is long-lasting, while the dynamic fatigue testing can be much faster; however, the dynamical changes due to fatigue are usually not taken into account and therefore the identified fatigue and structural parameters can be biased. In detail: damage accumulation results in structural changes (stiffness, damping) which are hard to measure in real time; further, structural changes change the dynamics of the loaded system and without taking this changes into account the fatigue load in the stress concentration zone can change significantly (even if the excitation remains the same). This research presents a new approach for accelerated vibration testing of real structures.
2014-06-30
Technical Paper
2014-01-2094
Matteo Kirchner, Eugene Nijman
Abstract Automotive industry is becoming more and more interested in assessing the noise of electric motors, since their integration in many types of road vehicles is rapidly growing in a market oriented to hybridization and electrification. The acoustic characterization of an electric motor is often being performed numerically, having as consequence the fact that the investigation is confined to one specific model belonging to one particular type of motor. This paper proposes an experimental airborne sound characterization methodology, suitable for any type of cylindrical source, based on a set of data acquired following a cylindrical Nearfield Acoustical Holography (NAH) scheme. Such an approach allows the evaluation of sound intensity, as well as pressure level and particle velocity.
2014-06-30
Technical Paper
2014-01-2093
Vishal Parmar, Daniele Di Rocco, Martin Sopouch, Philippe Albertini
Abstract Over the past 30 years, simulation of the N&V (Noise and Vibration) behaviour of automotive drivelines became an integral part of the powertrain development process. With current and future HEVs (Hybrid-Electrical Vehicles), additional phenomena and effects have entered the scene and need to be taken into account during layout/design as well as optimization phase. Beside effects directly associated with the e-components (namely electric whistle and whine), torque changes caused by activation/deactivation of the e-machine give rise to vibration issues (e.g. driveline shuffle or clonk) as well. This is in particular true for transient operation conditions like boosting and recuperation. Moreover, aspects of starting the Internal Combustion Engine (ICE) using the built-in e-machine in conjunction with the dynamic behaviour of torsional decoupling devices become increasingly important. In order to cope with above-mentioned effects a multi-physics simulation approach is required.
2014-06-30
Technical Paper
2014-01-2069
Barry M. James, Andreas Hofmann
Abstract The noise performance of fully electric vehicles is essential to ensure that they gain market acceptance. This can be a challenge for several reasons. Firstly, there is no masking from the internal combustion engine. Next, there is pressure to move to cost-efficient motor designs such as Switched Reluctance Motors, which have worse vibro-acoustic behaviour than their Permanent Magnet counterparts. Finally, power-dense, higher speed motors run closer fundamental frequency to the structural resonances of the system [1]. Experience has shown that this challenge is frequently not met. Reputable suppliers have designed and developed their “quiet” subsystems to state of the art levels, only to discover that the assembled E-powertrain is unacceptably noisy. The paper describes the process and arising results for the noise simulation of the complete powertrain.
2014-06-30
Journal Article
2014-01-2070
Jean-Baptiste Dupont, Racha Aydoun, Pascal Bouvet
Abstract The noise radiated by an electrical motor is very different from the one generated by an internal combustion engine. It is characterized by the emergence of high frequency pure tones that can be annoying and badly perceived by future drivers, even if the overall noise level is lower than that of a combustion engine. A simulation methodology has been proposed, consisting in a multi-physical approach to simulate the dynamic forces and noise radiated by electric motors. The principle is first to calculate the excitation due to electromagnetic phenomena (Maxwell forces) using an electromagnetic finite element solver. This excitation is then projected onto the structure mesh of the stator in order to calculate the dynamic response. Finally, the radiated sound power is calculated with the aid of a standard acoustic finite element method. The calculation methodology assumes a weak coupling between the different physical levels.
2014-06-30
Technical Paper
2014-01-2067
Michael Klanner, Mathias Mair, Franz Diwoky, Oszkar Biro, Katrin Ellermann
Abstract The noise vibration and harshness (NVH) simulation of electric machines becomes increasingly important due to the use of electric machines in vehicles. This paper describes a method to reduce the calculation time and required memory of the finite element NVH simulation of electrical machines. The stator of a synchronous electrical machine is modeled as a two-dimensional problem to reduce investigation effort. The electromagnetic forces acting on the stator are determined by FE-simulation in advance. Since these forces need to be transferred from the electromagnetic model to the structural model, a coupling algorithm is necessary. In order to reduce the number of nodes, which are involved in the coupling between the electromagnetic and structural model, multipoint constraints (MPC) are used to connect several coupling nodes to one new coupling node. For the definition of the new coupling nodes, the acting load is analyzed with a 2D-FFT.
2014-06-30
Technical Paper
2014-01-2068
Sameh AFFI
Abstract Many car manufacturers are introducing Stop & Start systems based on conventional ring gear starter, which represents an economical solution without heavy modifications of their existent architectures especially if they consider hybrid technology. However, this solution is unfortunately not very satisfying from NVH point of view. Indeed, customers usually accept a noisy and quite long engine restart when it happens only one time at the kick-off. However, for hybrid vehicles, an inaudible and quick restart is required because it happens without any drivers' demand and thus it may disturb them. In this paper, we focused on NVH analysis of engine restart sequence with conventional ring gear starter. Some solutions were tested in order to optimize restart duration and noise level.
2014-06-30
Journal Article
2014-01-2073
Koen Vansant, Hadrien Bériot, Claudio Bertolini, Giuseppe Miccoli
Abstract As the legislation for pass-by noise (PBN) has recently become more stringent, car manufacturers face again a challenging task to reach the new SPL objective (70dB(A)). A good design of the engine bay is therefore required to sufficiently attenuate the noise coming from sources as the engine and the intake. This involves proper design of the engine bay's panels including apertures, and a good selection of the type and location of acoustic treatments. For a given engine bay design, the PBN SPL results can be obtained with a PBN test or by an equivalent simulation. Using simulation models it is possible to create the perfect test environment virtually and moreover to obtain acoustic results for a large number of designs upfront of any actual testing or prototype.
2014-06-30
Journal Article
2014-01-2071
Albert Albers, Jan Fischer, David Landes, Matthias Behrendt
Abstract The driving comfort is an important factor for buying decisions. Especially for battery electric vehicles (BEV) the acoustic quality is an elementary distinguishing feature, since the masking of an internal combustion engine (ICE) is no longer present. Opposing the importance of the acoustic quality is the lack of knowledge of how to measure and interpret the high frequency noise generated by an electric powertrain with respect to the NVH behavior influencing the passengers [1, 2]. In this contribution a method for measuring and interpreting the transfer path of acoustic phenomena from the drivetrain of a battery electric vehicle into the passenger cabin is presented. Due to the lack of masking by the ICE in case of BEV, high frequency phenomena must be considered as well. In order to determine the airborne transfer function from the electric powertrain to the driver cabin, a dodecahedral speaker is used for reciprocal measurements.
2014-06-30
Technical Paper
2014-01-2074
Gilles Nghiem, Shanjin Wang
Abstract The vehicle pass-by noise regulation will change in the near future and noise limits will be lowered significantly. This evolution will require improvement of engine's sound radiation. On the other hand, under the current pressure for fuel economy, future engines will be more and more lightened, and this will have negative impact on engine's sound emission. Therefore, the requirements related to the new pass-by noise regulation should be taken into account in the design of new powertrains, and in some cases, innovative solutions must be developed in order to improve the level of noise of the engine while reducing the masse of the engine. One effective way is to optimize the design of some key engine parts, such as crankshaft and engine bottom structure.
2014-06-30
Technical Paper
2014-01-2078
Jean-Francois Rondeau, Ludovic Dejaeger, Antoine Guellec, Arnaud Caillet, Lars Bischoff
Abstract Strategies for weight reduction have driven the noise treatment advanced developments with a great success considering the already mastered weight decreases observed in the last years in the automotive industry. This is typically the case for all soft trims parts. In the early 2010's a typical european B-segment car soft trims weights indeed 30 to 40% less than in the early 2000's years. The main driver behind such a gap has been to combine insulation and absorption properties on a single part while increasing the number of layers. This product-process evolution was conducted using a significant improvement in the simulation capacities. In that sense, several studies presenting very good correlation results between Transmission Loss measurements and finite elements simulations on dashboard or floor insulators were presented. One may consider that those kinds of parts have already achieved a considerable improvement in performance.
2014-06-30
Technical Paper
2014-01-2072
Christoph Meier, Dirk Lieske, Stefan Bikker
Abstract Electric cars are getting popular more and more and the expectations of the customers are very challenging. Concerning comfort, the situation is clear: customers want an electric car to be quiet and without any annoying noise from the powertrain. To develop an electric powertrain with a minimum noise level and minimized whining it is necessary to have an accurate CAE-simulation and precise criteria to assess whining noise. Based on the experience with electric powertrains in research cars the CAE-modelling was improved and a new ‘whining intensity factor’ was acquired for the development of Daimler's electric cars. The results are a very low noise level and a minimized whining noise, nearly not noticeable giving a comfortable sound to the customers of the smart electric drive and the B-Class Electric Drive.
2014-06-30
Journal Article
2014-01-2079
Gregor Tanner, David J. Chappell, Dominik Löchel, Niels Søndergaard
Abstract Modelling the vibro-acoustic properties of mechanical built-up structures is a challenging task, especially in the mid to high frequency regime, even with the computational resources available today. Standard modelling tools for complex vehicle parts include finite and boundary element methods (FEM and BEM), as well as Multi-Body Simulations (MBS). These methods are, however, robust only in the low frequency regime. In particular, FEM is not scalable to higher frequencies due to the prohibitive increase in model size. We have recently developed a new method called Discrete Flow Mapping (DFM), which extends existing high frequency methods, such as Statistical Energy Analysis or the so-called Dynamical Energy Analysis (DEA), to work on meshed structures. It provides for the first time detailed spatial information about the vibrational energy of a whole built-up structure of arbitrary complexity in this frequency range.
2014-06-30
Technical Paper
2014-01-2077
Tom Knechten, Christophe Coster, Peter Van der Linden
Abstract The need for more durable mobility has led to a rapid introduction of new electric systems on vehicles. The result of the application of electrified drivelines is a shift in noise energy from the low mid frequencies towards the upper end of the audible range. Following this, the need for higher frequency noise control and accurate measurement has grown. The measurement of the acoustic transfer or vehicle body isolation at higher frequencies poses a challenge for the diffraction, source level and omni-directionality. This paper shows an improved method that increases the accuracy of acoustic transfer function measurements from the components to the ear at high frequencies. A simulation model based on the Boundary Element Methods(BEM) has been made to analyze higher frequency behavior of noise sources during reciprocal measurements up to 12 kHz. Some dedicated hardware was developed in combination with a new process.
2014-06-30
Journal Article
2014-01-2082
Rebecca Cowles, Andrew Shives, Daniel Rauchholz
Abstract To satisfy the increased expectations of customers, engineers are challenged to increase fuel economy while also improving noise, vibration, and harshness (NVH) performance. In order to improve fuel economy, engine compartment designs have become more compact with reduced air flow. Elevated temperatures caused by these designs can degrade the durability and acoustic performance of the fibrous acoustic insulator material. A typical method for protecting insulators from elevated temperatures is to apply an aluminum foil patch to the surface. However, foil patches can restrict the insulator's ability to absorb sound and can be difficult to apply to complex part shapes. Foil patches can be perforated to allow the insulator to absorb sound, but there is a cost penalty as well as potential for long term performance degradation due to blocked perforations. Since NVH targets are also increasing, it's important to maximize the benefit of each part.
2014-06-30
Technical Paper
2014-01-2083
Arnaud Caillet, Antoine Guellec, Denis Blanchet, Thomas Roy
Abstract Since the last decade, the automotive industry has expressed the need to better understand how the different trim parts interact together in a complete car up to 400 Hz for structureborne excitations. Classical FE methods in which the acoustic trim is represented as non-structural masses (NSM) and high damping or surface absorbers on the acoustic cavity can only be used at lower frequencies and do not provide insights into the interactions of the acoustic trims with the structure and the acoustic volume. It was demonstrated in several papers that modelling the acoustic components using the poroelastic finite element method (PEM) can yield accurate vibro-acoustic response such as transmission loss of a car component [1,2,3]. The increase of performance of today's computers and the further optimization of commercial simulation codes allow computations on full vehicle level [4,5,6] with adequate accuracy and computation times, which is essential for a car OEM.
2014-06-30
Journal Article
2014-01-2046
Matthias Frank, Franz Zotter, Alois Sontacchi, Stephan Brandl, Christian Kranzler
Abstract When employing in-car active sound generation (ASG) and active noise cancellation (ANC), the accurate knowledge of the vehicle interior sound pressure distribution in magnitude as well as phase is paramount. Revisiting the ANC concept, relevant boundary conditions in spatial sound fields will be addressed. Moreover, within this study the controllability and observability requirements in case of ASG and ANC were examined in detail. This investigation focuses on sound pressure measurements using a 24 channel microphone array at different heights near the head of the driver. A shaker at the firewall and four loudspeakers of an ordinary in-car sound system have been investigated in order to compare their sound fields. Measurements have been done for different numbers of passengers, with and without a dummy head and real person on the driver seat. Transfer functions have been determined with a log-swept sine technique.
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