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The noise radiated by electrical machines is due to the electromagnetic excitations applied to the structure of the machine. Even if the generated sound power levels are not as high as those typically emitted by internal combustion engines, they are characterized by the emergence of high frequency pure tones that can be annoying and badly perceived by users. The radiated noise is influenced by many parameters related to the structure and electromagnetic design of the machine. The supply strategy can play a key role as well. This paper present a 3-step simulation process. Electromagnetic excitations are estimated (finite element software) and projected onto the structure model of the machine. Dynamic response under realistic electromagnetic can be calculated. The last step is about the calculation of the radiated noise with the aid of typical acoustic methods.

In the context of the upcoming reduction of Pass-By-Noise limits in the EU regulations, automotive manufacturers need to implement new concepts of shielding package. ECOBEX is a French funded research project aiming at reducing the powertrain noise contribution of the vehicle, whilst restricting additional mass and cost. Bringing together OEM, raw materials suppliers, shielding manufacturers, universities and specialized consultants in this research program enabled innovations in materials, design, tests and computational methods. This paper will focus on a new procedure for the optimization of the shielding package, based on a precise 3D localization and quantification of the acoustic sources of the powertrain and on their implementation in an Energy Boundary Element model, computing the acoustic propagation. Intensity maps emphasized the dominant acoustic paths and highlighted mitigation opportunities in terms of absorption and insulation.

The recent use of electric motors for vehicle propulsion has stimulated the development of numerical methodologies to predict their noise and vibration behavior. These simulations generally use models based on an ideal electric motor. But sometimes acceleration and noise measurements on electric motors show unexpected harmonics that can generate acoustic issues. These harmonics are mainly due to the deviation of the manufactured parts from the nominal dimensions of the ideal machine. The rotor eccentricities are one of these deviations with an impact on acoustics of electric motors. Thus, the measurement of the rotor eccentricity becomes relevant to understand the phenomenon, quantify the deviation and then to use this data as an input in the numerical models. An innovative measurement method of rotor eccentricities using fiber optic displacement sensors is proposed.

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. It has been validated by comparison with the experiment.

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).

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. Even if the excitation due to electromagnetic phenomena of electric motors is well known, the link to the dynamic excitation generating vibrations and noise is not done. The purpose of this work is to propose 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 automotive industry has entered a phase of change due to environmental considerations. Hybrid and electric vehicles are emerging and with them the need to include these new technologies in the design process, especially in numerical simulation methods. Different types of electromagnetic excitation may occur in electric machines. In particular, Maxwell pressure is responsible for radial forces applied to electric motor stators, which can cause a deflection and possible acoustic radiation. This paper describes a complete approach to simulate the noise radiated by electric motor stators. The principle of this multiphysics method is first to calculate the excitation due to electromagnetic phenomena 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, radiated sound power is calculated with the aid of a finite element method.

Due to the increasing focus on noise and vibration for future vehicles, there is a need for a clear definition of the requirements between vehicle manufacturers and auxiliary suppliers. Auxiliary characterisations are also needed as input for structure-borne numerical prediction models. Strongly coupled systems are amongst the most difficult structure-borne noise issues, as the transmitted forces and powers are strongly dependent upon the mobilities of both the vibration source and receiver. The so-called “blocked forces” can be used as intrinsic source descriptions. The challenge is then to design auxiliary test benches perfectly rigid in the frequency range of interest. The current paper is based on the French research program MACOVAM dedicated to the vibro-acoustic characterisation of oil pumps for truck engines. An original test bench was designed to measure quasi-blocked forces over the [150 Hz-2800 Hz] frequency range.

In the context of more and more drastic noise regulation and increasing customers demand for lower noise annoyance, acoustic shields become essential for a wide range of vehicles. Due to reduced development time, acoustic design must start in the early stage of industrial projects, requiring precise and reactive prediction tools. The most widely used computation methods perform a numerical resolution of Helmholtz equation with a spatial discretization into Finite Elements or Boundary Elements. These methods are efficient in the low frequency range, but they reach their limits at higher frequencies, due to high computational cost, very precise mesh required, and high sensitivity to geometry and frequency. Then Ray Tracing techniques may be an alternative in some cases, but diffused reflection is generally ignored and convergence is not always reached, observation points receiving too few rays.

The paper presents an energetic post-processing methodology for large-scale vibro-acoustic finite element models. Starting from a dynamic and an acoustic modal basis produced by a finite element analysis (FEA), the methodology produces: 1 synthetic and pertinent energetic outputs; 2 optimal SEA partitions of the finite element mesh; 3 quality indicators of existing SEA partitions. The methodology involves six different steps, some required, some optional: 1 automatic partitioning of the FEA model in patches; 2 calculation of distribution matrices; 3 definition of mechanical loads; 4 definition of damping characteristics; 5 modal-based vibro-acoustic response calculation; 6 energetic post-processing; 7 automatic partitioning in SEA subsystems; 8 verification of existing SEA partitions. Each step will be presented in turn. The methodology will be illustrated by application of the successive steps to a Renault Laguna body and an Alstom two-storey TGV train section.