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Govindswamy K.,FEV Inc. | Eisele G.,FEV Motorentechnik GmbH
SAE Technical Papers | Year: 2011

The electrification of vehicle propulsion has caused a significant change in many areas including the world of vehicle acoustics. Comments from the media currently range from "silently hums the future" to "electric car roars with V8 sound". Decades of experience in designing brand-specific vehicle sound based on noise and vibration generated by combustion engines cannot be simply transferred to the upcoming vehicles driven purely by electric powertrains. Although electric vehicles are almost always considerably quieter than those powered by internal combustion engines, the interior noise is characterized by high-frequency noise components which can be subjectively perceived as annoying and unpleasant. Moreover, such disturbing noise is no longer masked by combustion engine noise. Fundamental questions regarding the sound design of electric vehicles have yet to be answered: it remains unclear what exactly the interior noise of an electric vehicle should sound like. Also questions regarding the approach to achieving a particular interior sound (e.g., use of artificially generated noise for desired sound) are still open. There is also an ongoing debate on the need for electric vehicles to emit additional noise in order to prevent the endangerment of pedestrians. The use of additional noise sources could work against the hope for noise reduction. This paper is intended as a contribution to the current discussion on what the target noise of electric vehicles could sound like and what possibilities currently exist for NVH engineers to design the sound of electric cars. Copyright © 2011 SAE International. Source

Fev Inc. | Date: 2013-10-08

computer hardware and software sold as a unit for power train analysis.

Wellmann T.,FEV Inc. | Govindswamy K.,FEV Inc. | Eisele G.,FEV Motorentechnik GmbH
SAE Technical Papers | Year: 2011

It is important to develop powertrain NVH characteristics with the goal of ultimately influencing/improving the in-vehicle NVH behavior since this is what matters to the end customer. One development tool called dB(VINS) based on a process called Vehicle Interior Noise Simulation (VINS) is used for determining interior vehicle noise based on powertrain level measurements (mount vibration and radiated noise) in combination with standardized vehicle transfer functions. Although this method is not intended to replace a complete transfer path analysis and does not take any vehicle specific sensitivity into account, it allows for powertrain-induced interior vehicle noise assessments without having an actual test vehicle available. Such a technique allows for vehicle centric powertrain NVH development right from an early vehicle development stage. While this is a proven tool for powertrain level sound quality evaluations and correlates well for front wheel drive (FWD) vehicles, the interior noise for rear wheel drive (RWD) vehicles is often under-predicted on account of missing contributions from the driveline. RWD vehicles can have significant contributions through the rear axle mounting paths, especially for powertrains with manual transmissions or during lock up of the torque converter clutch with conventional automatic transmissions. Torsional vibrations are transmitted through the driveline, causing reaction forces at the rear axle, resulting in driveline boom. Resonances in the driveline system typically amplify the driveline boom excitation. This publication extends the dB(VINS) approach for interior noise simulation by determining the driveline-induced noise of a RWD vehicle. The influence of the structureborne path and firing order related torsional vibration through the rear axle is demonstrated with a time domain transfer path process. Generic transfer functions for extension of the dB(VINS) process are developed in order to capture driveline noise share of RWD vehicles. In addition to vehicle measurements, a multi body simulation (MBS) model is generated and rear axle vibrations are calculated via MBS simulation of the vehicle driveline. The results are discussed in the context of driveline NVH integration and appropriate conclusions provided. Copyright © 2011 SAE International. Source

Govindswamy K.,FEV Inc. | Tomazic D.,FEV Inc. | Genender P.,FEV GmbH | Schuermann G.,FEV GmbH
SAE Technical Papers | Year: 2013

The electrification of vehicle propulsion has changed the landscape of vehicle NVH. Pure electric vehicles (EV) are almost always quieter than those powered by internal combustion engines. However, one of the key challenges with the development of range extended electric vehicles (ReEV) is the NVH behavior of the vehicle. Specifically, the transition from the EV mode to one where the range extender engine is operational can cause significant NVH issues. In addition, the operation of the range extender engine relative to various driving conditions can also pose significant NVH concerns. In this paper internal combustion engines are examined in terms of their acoustic behavior when used as range extenders. This is done by simulating the vibrations at the engine mounting positions as well as the intake and exhaust orifice noise. By using a transfer path synthesis, interior noise components of the range extenders are calculated from these excitations. The results from this study show a few promising internal combustion engines concepts such as the inline-six-cylinder engine, the single-rotor Wankel engine, and the two-cylinder-boxer engine in combination with a neutral torque axis mounting. When using other mounting positions, an internal rolling moment compensation system is shown to reduce the engine vibrations and hence the interior noise. Copyright © 2013 SAE International. Source

Tousignant T.,FEV Inc. | Govindswamy K.,FEV Inc.
SAE Technical Papers | Year: 2014

Increased customer expectation for NVH refinement creates a significant challenge for the integration of Diesel powertrains into passenger vehicles that might have been initially developed for gasoline engine applications. A significant factor in the refinement of Diesel powertrain sound quality is calibration optimization for NVH, which is often constrained by performance, emissions and fuel economy requirements. Vehicle level enablers add cost and weight to the vehicle and are generally bounded by vehicle architecture, particularly when dealing with a carry-over vehicle platform, as is often the case for many vehicle programs. These constraints are compounded by the need to make program critical sound package content decisions well before the availability of prototype vehicles with the right powertrain. In this paper, a case study on NVH development for integration of a light duty Diesel powertrain is presented. A process, based on a time-domain transfer path methodology was applied to provide focused engineering development of powertrain and vehicle level NVH enablers. Specifically, this paper describes the process of virtually installing a Diesel powertrain into a carryover gasoline vehicle, then later into a prototype development vehicle and target vehicle. Results from the "virtual swaps" were utilized to assess the gaps to NVH targets and to develop a focused plan for development of powertrain and vehicle level NVH enablers. Copyright © 2014 SAE International. Source

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