Refine Your Search

Topic

Author

Affiliation

Search Results

Technical Paper

ANC: A Low-cost Implementation Perspective

2022-06-15
2022-01-0967
In the present work, we describe a low-cost implementation of an Active Noise Cancellation (ANC) system. The most interesting feature of our implementation is the use of general-purpose hardware, without the need of expensive and hard-to-program Digital Signal Processing (DSP) devices. In particular, the reference signals, collected with accelerometers properly placed on noise-generating parts and the error feedback signals are collected by means of an USB interface. All signal processing, aimed at primary path estimation and anti-noise audio signal generation, is performed using Simulink running on a commercial mini PC. The Exponential Sine Sweep (ESS) method is adopted for the measurement of the secondary path from the cancellation loudspeakers to the error microphones. An adaptive Filtered-X Least Mean Square (LMS) algorithm determines the anti-noise audio signal to be emitted.
Technical Paper

A Trend Line Analysis of the Insertion Loss Test Data and Application to Sound Transmission Loss Simulation

2022-06-15
2022-01-0959
In this paper, an application process is studied at which insertion loss (IL) test data of sound barrier assemblies are utilized for the sound transmission loss (STL) simulation of the trimmed dash structure. The considered sound barrier assemblies were composed of a felt layer, a mass layer, and a decoupler layer. Flat samples of sound barrier assemblies with several different thicknesses were prepared, and ILs of them were measured by using a sound transmission loss facility. Flat samples were assumed to have mass-spring resonance frequencies. The mass was set as the area mass of the sound barrier layer of the felt layer and the mass layer. The spring constant of the decoupler layer was assumed as the multiplication of that of an air spring and a spring correction factor. At the beginning, the spring correction factor was assumed to be 1, and the measured IL data vs frequencies are converted to IL data vs frequency ratios, frequency f over the resonance frequency fres.
Technical Paper

Parametric Model Order Reduction for Vibroacoustic Metamaterials based on Modal Superposition

2022-06-15
2022-01-0942
Vibroacoustic Metamaterials (VAMM) have recently shown great potential in the elimination of noise and vibration in targeted and tunable frequency regions. The so-called stop band behavior is mainly driven by small resonance structures on a subwavelength scale. Due to the complex material and geometry composition, stochastic methods for uncertainty quantification, model updating, and optimization are necessary in the design and validation process of VAMM. Those methods require to repeatedly solve Finite Element (FE) models with slightly changed parameters and can become computationally challenging for large numerical models. Hence, the need for Parametric Model Order Reduction (PMOR) techniques arise to reduce the computational burden. For VAMM, consisting of many substructures, common PMOR methods based on Component Mode Synthesis (CMS) can become cumbersome to set up and numerically challenging.
Technical Paper

Assessing low frequency flow noise based on an experimentally validated modal substructuring strategy featuring non-conforming grids

2022-06-15
2022-01-0939
The continuous encouragement of lightweight design in modern vehicles demands a reliable and efficient method to predict and ameliorate the interior acoustic comfort for passengers. Due to considerable psychological effects on stress and concentration, the low frequency contribution plays a vital rule regarding interior noise perception. Apart other contributors, low frequency noise can be induced by transient aerodynamic excitation and the related structural vibrations. Assessing this disturbancy requires the reliable simulation of the complex multi-physical mechanisms involved, such as transient aerodynamics, structural dynamics and acoustics. The domain of structural dynamics is particularly sensitive regarding the modelling of attachments restraining the vibrational behavior of incorporated membrane-like structures. In a later development stage, when prototypes are available, it is therefore desirable to replace or update purely numerical models with experimental data.
Technical Paper

Variational Autoencoders for Dimensionality Reduction of Automotive Vibroacoustic Models

2022-06-15
2022-01-0941
In order to predict reality as accurately as possible leads to the fact that numerical models in automotive vibroacoustic problems become increasingly high dimensional. This makes applications with a large number of model evaluations, e.g. optimization tasks or uncertainty quantification hard to solve, as they become computationally very expensive. Engineers are thus faced with the challenge of making decisions based on a limited number of model evaluations, which increases the need for data-efficient methods and reduced order models. In this contribution, variational autoencoders (VAEs) are used to reduce the dimensionality of the vibroacoustic model of a vehicle body and to find a low-dimensional latent representation of the system.
Technical Paper

Effects of Boundary Layer and Local Volumetric Cells Refinements on Compressor Direct Noise Computation

2022-06-15
2022-01-0933
The use of turbochargers with downsized internal combustion engines improves road vehicles’ energy efficiency but introduces additional sound sources of strong acoustic annoyance on the turbocharger’s compressor side. In the present study, direct noise computation (DNC) is carried out on a passenger vehicle turbocharger compressor. The work focuses on assessing the influence of grid parameters on the acoustic predictions, to further advance the maturity of the acoustic modelling of such machines with complex three-dimensional features. The DES study investigates the influence of the inflation layers characteristics, and of the spatial resolution of the mesh, on the simulated acoustic signatures. In the core mesh, refinements are applied in areas of major acoustic production, to generate cells with sizes proportional to the local Taylor microscale values.
Technical Paper

Aero-acoustic source terms from Large-Eddy Simulation in turbulent pipe flow

2022-06-15
2022-01-0937
In the acoustic design of electric vehicles, novel simulation technologies for predicting relevant sound sources early in the design state become increasingly important. This requires accurate numerical methods to describe these phenomena. The present study computationally investigates the flow-induced noise from aero acoustic sound sources, generated in turbulent pipe flow. The analysis follows a hybrid approach, where the acoustic sound field is predicted separately from the underlying the turbulent flow field, however supplied with acoustic source terms from an incompressible flow simulation of the considered configuration in the limit of low Mach number. Source terms from for use as input into different acoustic analogies, the Lighthill’s wave equation, the vortex-sound theory, and the Perturbed Convective Wave Equation (PCWE) are computed performing incompressible Direct Numerical Simulation (DNS) and Large-Eddy Simulations (LES) of fully developed pipe flow.
Technical Paper

Validation of Combining Compressible CFD Results with Statistical Energy Analysis for Vehicle Interior Noise Simulation

2022-06-15
2022-01-0936
Already a concern and a main customer satisfaction complaint for many years, wind noise for passenger vehicle is an increasingly important concern as the masking effects of internal combustion engines is phased out for Electric Vehicles which replace engine, intake and exhaust noise with electric component and other accessory noise. Acoustic wind tunnel testing is expensive and time consuming and can generally only provide useful results near the end of the vehicle design process with mature prototypes, and this is at a design phase where changes or countermeasures to reduce wind noise may be difficult or at the least costly. This paper represents a validation case for a production vehicle where a compressible Computational Fluid Dynamics (CFD) model was used to calculate surface pressures on the vehicle.
Technical Paper

Time-Domain Simulation Approach for the Electromagnetically Excited Vibrations of Squirrel-Cage Induction Machine Drives under Pulse-Width Modulated Supply

2022-06-15
2022-01-0931
One key point of the design process of electrified drive trains is the optimization regarding noise, vibration and harshness (NVH). An important task in this regard is to identify NVH related issues in early design phases by means of computer simulations. A main contributor for vibrations and noises are electromagnetically excited forces and torque stemming from the electric motor that propagate to housing and transmission. In our current study we explore the whole multi-physical simulation workflow from electromagnetics and structural dynamics to acoustics. In electromagnetic simulations, forces and torque signals are calculated for specific speed-torque operation points. In order to consider all system non-linearities correctly, time-domain simulations are carried out. The electric motor investigated in this study is a squirrel-cage induction machine. For this machine type, the simulation effort with full transient numerical methods like finite element analysis is very high.
Technical Paper

Using Analytical Techniques to Understand the Impacts Intelligent Thermal Management Has on Piston NVH

2022-06-15
2022-01-0930
In order to align with net-zero CO2 ambitions, automotive OEMs have been developing increasingly sophisticated strategies to minimise the impact that combustion engines have on the environment. Intelligent thermal management systems have a positive impact on friction generated in the power cylinder by improving the warmup rate of cylinder liners and heads. This increase in temperature results in an improved frictional performance and cycle averaged fuel consumption, but also increases the dynamic piston to liner clearance and therefore the propensity for piston slap. In low temperatures this piston slap can substantially decrease the NVH quality to unacceptable levels. Using analytical techniques, it is possible to model the thermo-structural and NVH response of the power cylinder with different warm up strategies.
Technical Paper

Efficient prediction and analysis of the noise radiated by an electric powertrain

2022-06-15
2022-01-0934
Reducing the emitted noise from vehicles is a primary issue for automotive OEMs due to the constant evolution of the noise regulations. In the context of electric powertrains, virtual prototyping has proven to be a cost-efficient alternative to the build-test process, especially in early design stage and/or if optimization is targeted. Due to the multiphysics nature of the model, the full simulation chain involves multiple components, each having its own specific modelling attributes. The difficulty then resides in the parts assembly, solving issues like mesh-to-mesh projections, time to frequency-domain transformation, 2d-axisymmetric to 3d mapping, data formatting and management, unit and local coordinate systems,… This paper presents an environment that allows for the prediction and analysis of the noise radiated by electric automotive powertrains.
Technical Paper

Characterization and modelling of mounts for electric powertrains

2022-06-15
2022-01-0986
The topic of this paper is to deal with the filtering of medium and high frequency excitations generated by electrified powertrains. It is now recognized that the whining noise generated by the electromagnetic forces and/or the meshing process of the transmission can propagate to the car-body through the rubber mounts. In the design phase, the prediction of the structure borne contribution requires a good knowledge of the dynamic behavior of the rubber mounts. The main issue is the stiffness of the mounts which cannot be modeled as pure springs. In fact, the dynamic behavior of a mount is governed by the material rheology and its internal resonances. The work presented in this paper propose a simulation workflow for the rubber mounts dynamic model and a methodology for the dynamic stiffness measurement including the sensitivity with the preload and with the amplitude of the excitation. Finally, experimental and digital data are compared to assess the simulation method.
Technical Paper

A Coupled Simulation Approach for the Quantification of Impact Events in Automotive Applications

2022-06-15
2022-01-0985
Squeak and Rattle are the most obnoxious noises, affecting the perceived quality of an automobile interior. Minimizing or eliminating these transient events poses a great challenge in vehicle construction as they are generally discovered late in the product development cycle. Identifying and quantifying these issues at the design and virtual validation stage is of prime importance. Current simulation methodologies estimate the occurrence of these events by measuring the relative displacement between the interacting parts. Solving this problem using linear simulations do not accurately reflect real-world non-linear mechanical behavior and most importantly, quantifying the noise caused by these impact events. Capturing a suitable impact behavior is essential along with the quantification of noise generated by these events is necessary for understanding the severity of the problem.
Technical Paper

An efficient methodology to predict the dynamic instabilities of a frictional system

2022-06-15
2022-01-0984
Stochastic Finite Elements Method (SFEM) is applied in many fields. For instance, in frictional systems, it helps quantify uncertainties due to a generalized lack of knowledge about the involved process and thus, provides a more reliable prediction of the dynamic instabilities. Usually, SFEM is coupled with sensitivity theory to investigate the effect of a given input on the output. However, the available methods which often couple Monte-Carlo (MC) algorithm with the Finite Element (FE) method have a computational cost that scales linearly as a number of stochastic iteration N and input parameters k (i.e., t ~ N k). For an interesting convergence property, the magnitude of N must be on the order of thousands or even millions. Hence, for a frictional system with 5 random variables and requires 15 min of CPU per run, the computational cost will exceed 52 days (!).
Technical Paper

Analytical and Numerical Models of the Sound Radiated by Fully Clamped Rectangular Vibrating Plates

2022-06-15
2022-01-0973
In the present work, fully clamped rectangular vibrating plates are investigated: the response is calculated under steady-state excitation determined by the application of a harmonic point force, and the consequent sound radiation is evaluated. An isotropic, undamped material was employed, having the mechanical properties (density, Young’s modulus and Poisson’s ratio) of the aluminium. The study is carried out both theoretically and numerically. At first, the analytical solution of the motion equation for a fully clamped plate is calculated by means of a MATLAB implementation. The solution is based on the Principle of Virtual Work, calculating the displacement as a function of the frequency at the nodes of a rectangular mesh. The monopole approximation of the Rayleigh’s integral is then used to estimate the sound radiated in free field condition. The numerical solution is evaluated using COMSOL Multiphysics, employing the Finite Elements Method (FEM).
Technical Paper

Gaussian processes for transfer path analysis applied on vehicle body vibration problems

2022-06-15
2022-01-0948
Transfer path analyses of vehicle bodies are widely considered to be an important tool in the noise, vibration and harshness design process, as they enable the identification of the dominating transfer paths in vibration problems. It is highly beneficial to model uncertain parameters in early development stages due to the absence of detailed information on the component design. Therefore, parameter studies are conducted in order to account for the sensitivities of the transfer paths with respect to the varying input parameters of the chassis components. To date, these studies are mainly conducted by performing sampling-based finite element simulations, e.g., with Latin Hypercube or Monte Carlo sampling methods. In the scope of a sensitivity analysis, however, a great number of large-scale finite element simulations is required, which leads to extremely high computational costs and time expenses.
Technical Paper

Mastering uncertainty in model-based prediction of vibroacoustic vehicle properties

2022-06-15
2022-01-0989
Vibroacoustic properties specify among others the quality of vehicles and contribute to customer satisfaction. In early design phases a finite element analysis is usually carried out to predict and design vibroacoustic properties. Models are simplified to predict vibroacoustic properties with reasonable computational effort. For example, substructures such as seats are reduced to point masses. Especially in the early design phase, this lack of knowledge leads to uncertainty. Uncertainty is only partially taken into account yet, resulting in inaccurate model predictions. This paper proposes a three-part approach, which aims to improve the model-based predictions of the vibroacoustic properties by mastering uncertainty. First, structural uncertainty is also considered in addition to the well-known data uncertainty and model uncertainty.
Technical Paper

On the Calculation of Modal Damping Ratios

2022-06-15
2022-01-0945
The prediction of the sound characteristic of a drive train in early development stages poses a significant competitive advantage to specifically design the sound of e.g. a vehicle. However, at the state of the art, the structural behavior cannot be predicted with satisfactory accuracy due to the various and sensitive mechanisms which contribute to it. In the case of complex structures like electric motors or even complete drive trains, usually model order reduction and linearization techniques like the modal superposition method are employed to reduce the calculation effort and obtain usable models for transient time domain simulations. The three main force contributions which have to be considered are spring forces, inertia forces and damping forces. The former two arise from the Youngs-Modulus and the mass density. Both material parameters are relatively constant over a wide range of boundary conditions and therefor easy to calculate.
Technical Paper

Modeling and controling acoustic performance of heterogenous materials made of recycled foams

2022-06-15
2022-01-0962
Recycling channels for foam materials, especially mattress foams, are set up. The foams are generally crushed into flakes and then assembled resulting in heterogeneous materials. These materials are more valuable if their properties are controlled. This work focuses on their acoustical properties. First, the properties of initial foams have to be estimated and the assembling process has to be analyzed in order to model the acoustic behavior of the reconstructed heterogeneous materials. The foams flakes are assembled with a binder and compressed during the manufacturing process. This work presents the methodology set up to predict the sound absorption of such heterogeneous materials based on recycled foams, from the estimation of the raw material properties to the final assembly. First, a large number of foams were measured in order to distinguish categories of materials. The data is stored in a database management software in order to perform some statistical analysis.
Technical Paper

An Experimental Study on Factors That Influence Encapsulation Efficiency

2022-06-15
2022-01-0958
Absorptive and isolating encapsulations are commonly encountered on different noise-emitting components within the car industry. Not least for electric drive units, whose air borne noise shares often are dominant in the kHz region, encapsulations can provide a cost and weight efficient noise abatement solution. The main constrains related to the acoustic performance when designing an encapsulation for electric drive units are surface coverage due to geometrical complexities, allowable package space (setting limits for maximum thickness of the encapsulation), weight and finally cost. The numerical simulation techniques for quantifying the acoustic performance in terms of insertion loss are challenging, e.g. since the encapsulations are partly compressed and far from homogeneous. Impedance tube measurements of absorption and transmission loss are standard for material samples, but the link between those metrics and the insertion loss of the complete encapsulation has been unknown.
X