Noise, Vibration and Harshness (NVH) of Electric Powertrains: Electric Motor Whistling vs Transmission Whining
Identifying the electromechanical coupling in e-powertrains and reducing the impact of its effect on e-motor whistling and transmission whining noise, vibration and harshness.
The transition from Internal Combustion Engines (ICE) to Electric Vehicles (EVs) is driven by a collective pursuit of environmental sustainability, cost savings, and compliance of OEMs with stringent emissions regulations. However, new challenges to the NVH analysis of vehicles are introduced.
While ICEs tend to be louder, they emit sound in a broadband manner usually below 1 kHz. E-powertrains are quieter, but radiate noise in distinct frequencies governed by the powertrain topology and motor speed, at frequencies that can be higher than 10 kHz.
Two key contributors are usually present: e-motor whistling and gear whining. The electromagnetic forces acting on the motor’s stator and rotor are the source of whistling. Gear whining occurs because of the time-varying meshing stiffness of the gears. The tonal behaviour from these two sources can have a detrimental effect on the perceived sound quality of EVs.
Our Aim
Our research aims to identify the electromechanical coupling in e-powertrains and its effect on e-motor whistling and transmission whining NVH. We develop novel design methods to reduce their severity and avoid costly remedial NVH measures later in the development process.
Our Research
We employ fully flexible 3D multi-body dynamics to capture the contributions from the electromagnetic forces and the gear meshing, along with local non-linearities and predict the surface vibration of the e-powertrain housing along with the radiated noise.
Artificial Neural Networks
In order to provide fast design solutions tackling the perception of the tonal content of radiated noise, we develop artificial neural networks (ANNs) to optimise the powertrain and assess psychoacoustic features based on bearing forces transmitted to the housing. We use the Prominence Ratio (PR) metric to assess if a frequency in the noise spectrum will be perceived as tonal or not.
The effects of electromechanical coupling
Our applied research also investigates the effects of the electromechanical coupling on the natural frequencies and mode shape of the powertrain, identifying potentially aggressive whistling or whining for practical design solutions.
Reduced-order models for NVH predictions
Finally, we develop reduced-order models for NVH predictions in e-powertrains using 2-Dimensional (2D) multiphysics, delivering results within minutes for Permanent Magnet Synchronous Machines under load. The system's vibroacoustic response is computed by employing equivalent 2D structural models that represent the stator, and acoustic analyses is performed over the complete speed range of the e-motor.
Research outcomes
By utilizing numerical and analytical expressions, our methods provide direct insight into the NVH generation mechanisms of e-powertrains, often slicing the simulation time that is required by complex finite-element based methodologies. These benefits are paramount for NVH engineers, leading to quieter and more refined e-powertrains within shorter development times.
Our research is funded by the Engineering and Physical Sciences Research Council (EP/T518098/1 – DTP 2020-2021 黑料网) & (EP/V053353/1 – Automotive electric powertrain whistling and whining: fundamental root cause analysis to novel solutions) and UK Research and Innovation (2585407 – Electric motor and transmission coupled vibro-acoustics of electric powertrains).
Research dissemination
Our research has been promoted and disseminated at International Conferences, such as Aachen Acoustics Colloquium, ISNVH, NAFEMS, SAE World Congress and via social media channels.
Our research leads to fundamental understanding of the NVH generation mechanisms in e-powertrains and reduced simulations times, assisting the designers to deliver quiet powertrains within shorter development cycles.
Research members
Selected publications
- Andreou, P, Theodossiades, S, Hajjaj, AZ, Mohammadpour, M, Ricardo Souza, M (2024) . SAE Technical Papers. DOI: 10.4271/2024-01-2945.
- Ricardo Souza, M, Offner, G, Mohammadpour, M, Andreou, P, Theodossiades, S (2024) . SAE Technical Papers. DOI: 10.4271/2024-01-2913.
- Morris, N, Andreou, P, Ricardo Souza, M, Mohammad pour, M, Theodossiades, S (2024) , Elsevier, pp.41-56, ISBN: 9780443140754.
- Souza, MR, Haris, A, Rodrigues, L, Offner, G, Sopouch, M, Diwoky, F, Mohammad-Pour, M, Theodossiades, S (2024) , Meccanica, 59(3), pp.433-459, ISSN: 0025-6455. DOI: 10.1007/s11012-024-01753-x.
- Andreou, P, Hajjaj, A, Mohammad-Pour, M, Theodossiades, S (2023) , IEEE Transactions on Transportation Electrification, ISSN: 2332-7782. DOI: 10.1109/TTE.2023.3325350.
- Theodossiades, S, Morris, N, Mohammadpour, M (2022) . In Advances in Engine and Powertrain Research and Technology, Springer International Publishing, pp.267-290, ISBN: 9783030918682. DOI: 10.1007/978-3-030-91869-9_11.
- Souza, M.R., Mohammadpour, M., Theodossiades, S., Diwoky, F. et al., “NVH of Electric Motors - A Study on Potential NVH Metric,” in Aachen Acoustics Colloquium Proceedings, Aachen, 2022.
- Andreou, P, Zemni, AHE, Mohammad-Pour, M, Theodossiades, S (2022) . In 53rd Spanish Congress of Acoustics 2022; Proceedings of the Spanish Congress of Acoustics, Alicante, Spain.