Master Thesis :NVH analysis and optimization of an electric powertrain

Background of thesis project
Because of its compact shape and high power density, the permanent magnet synchronous motor (PMSM) appears to be better as a drive motor for electric construction machines (ECMs). However, as compared to conventional construction machines, the motor-driven machine has exhibited a different noise profile as a result of the shift in noise excitation source. The dramatic increase in high-frequency noises is particularly noticeable in this scenario. Furthermore, some of these high-frequency noises are distributed in the frequency range that is sensitive to human hearing, causing operators to feel highly uneasy.

Furthermore, gear whine noise emitted from the electric powertrain system could significantly affect driving comfort and has become an important NVH problem.

The motor's electromagnetic forces and the reducer's gear-meshing forces could create structural vibration and whining noise with clear order characteristics. As a result, it's critical to look into the NVH characteristics of PMSM and reducer for ECMs.

Computer-aided engineering (CAE) based vibration and sound simulation is a key approach for studying and optimizing electric powertrain NVH behavior, especially in the early stages of design. To put it another way, being able to forecast the noise and vibration harshness (NVH) behavior of an electric drive used in ECMs without having to run experimental solutions can save a company a lot of time and money.

So, the goal of this thesis is to investigate and describe a full CAE simulation process for the electromagnetic, electromechanical, vibro-acoustic, and optimization of electric powertrains.

The Division of Driveline & Electromobility Systems at the Technical Center in Eskilstuna is primarily responsible for this development.

Suitable background
  • The ideal student(s) will possess good communications skills in English (written and verbal), show a high level of initiative, be self-driven, have good analytical capabilities and have a high interest in computer-aided engineering (CAE) solutions for NVH on electric powertrains.
  • The successful candidate should have strong technical skills and should be willing perform measurements.
  • The candidate should have a bachelor’s degree and is now completing his/her Masters.
  • Any experience within the field of vehicle engineering is an advantage and relevant courses within the subject of NVH is a merit
Description of thesis work
Noise and vibrations of electrical machines are mainly due to electromagnetically excited sources (magnetostriction and Maxwell forces) and mechanical sources. In other words, sources of electromagnetic vibrations have the cogging torque, torque ripple, and time-varying traction. Sources of mechanical vibration have rotor dynamic, rotor unbalance, bearings, flexible shaft etc. Also, the radial force which is a force between rotor and stator in excited force. In order to reach the specific NVH targets, methods based on computer-aided engineering (CAE) have to be developed for electric motors both for mastering the excitations from electromagnetic sources and for improving the NVH responses from the whole powertrain structure. The CAE simulation process for investigating NVH of electric powertrain is shown in Figure 1. This complete simulation approach allows to investigate the electromagnetic behavior of the machine, especially the coupling between supply currents and the magnetic design, the coupling of magnetic forces in the air gap with modal behavior of the powertrain, and to quantify the vibration levels on the whole powertrain in all motor working conditions and in all the frequency ranges. Also it allows to understand the radiated noise by electric motors and powertrain assembly.

The aim of the thesis work is to develop a method based on “CAE solution approach” for investigating the NVH characteristics of electric powertrain used in ECMs. This thesis work also aims to study on the optimization of electric powertrain.
The main activities are:
  • Initially, Study/collect and pre-process the related knowledge on the development of electric powertrain in the driveline & electromobility organization
    • Then, electromagnetic forces should be calculated, taking into account the motor technology, the torque and the rotation speed. These excitation forces are then used as input for the 3D powertrain model including the rotor, the stator, the stator housing, the gearbox and other accessory parts.
    • The dynamic finite element model of the electric motor needs to be established considering the electromagnetic excitation of motor and calculate the modal frequency response of the motor.
    • Find the vibro-acoustic behavior of the motor.
    • Investigate the NVH behavior of the complete electric powertrain assembly considering both electrical and mechanical sources of excitations, and to quantify the vibration levels on the whole powertrain in all motor working conditions and in all the frequency ranges.
    • Also, analyze the radiated noise generated by both the electric motor and also the gear reducer, leveraging multidisciplinary computer-aided engineering analyses
  • Analyze and compare results that are predicted by different methods
  • Recommend a potential solution for having optimized electric powertrain for NVH.
A full report of the work carried out will be prepared and presented to staff at Volvo CE. It will be required for the student to perform the thesis at Volvo CE in Eskilstuna.

Number of Students: Two
One is for performing CAE simulations on motor [main task includes (a) to (c) as above]
Other student is for performing CAE simulations on the complete electric powertrain assembly [main task includes (d) to (e) as above]
Thesis Level: Master
Language: English

Starting date: 2nd Feb 2022

The supervisor for this thesis project is:

Ramkumar Kandasamy Ph.D
Driveline systems | Transmission Development,
Volvo Construction Equipment,
CE44440, TCC Building,
SE-631 85 Eskilstuna, Sweden.
Telephone: +46 (0)16 201 9984
Mobile: +46 769409984
E-mail: ramkumar.kandasamy@volvo.com

The Volvo Group drives prosperity through transport solutions, offering trucks, buses, construction equipment, power solutions for marine and industrial applications, financing and services that increase our customers’ uptime and productivity. Founded in 1927, the Volvo Group is committed to shaping the future landscape of sustainable transport and infrastructure solutions. Countless career opportunities are offered across the group’s leading brands and entities that share a culture of Trust, Passion, High Performance, Change and Customer Success. 

Volvo Construction Equipment is a global company driven by passion, curiosity and by our purpose: to build the world we want to live in. We believe that only through imagination and teamwork can we develop a world that is cleaner, smarter and more connected. Our company culture reflects this belief through the care and trust it places in our customers, employees and suppliers. People are at the heart of our business. It is through our strong network of talented, enquiring and innovative minds that we have been able to pave the way towards a more sustainable future. The global construction industry is our arena and our employees are our greatest assets.

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