Automotive electric powertrain whistling and whining: fundamental root cause analysis to novel solutions

“零排放之路”战略使英国在设计和制造零排放汽车方面走在了前列，新的汽油/柴油轿车和货车的销售计划在2040年前结束(根据最近的政府公告，可能在2030年前结束)。向更清洁、更安静的城市发展的战略加速了电动汽车(EVS)销售的趋势。然而，与流行的观点相反，电动汽车并不是沉默的。在没有内燃机噪声屏蔽的情况下，电机和传动系统发出的其他声音变得更加明显(主要是在中高车速下)。这对汽车原始设备制造商来说是一个重大挑战，他们需要调整他们的噪声、振动和粗糙度(NVH)设计方法，以适应“新的”电动(e-)动力总成环境。此外，必须在车辆NVH性能(和NVH组件重量)和由于需要沉重的电池组来增加行驶里程而导致的其他重量增加之间找到最佳平衡。电动汽车中NVH的一个重要问题是音调电动马达哨声(在转子速度的谐波处，取决于电机极数)。这是由电磁力产生的，电磁力激励电动马达和传动系外壳。噪声被动力总成结构放大，特别是定子及其外壳。增加功率和缩小电动马达尺寸是关键的商业需求，但对哨声噪音有不利影响。除此之外，电动马达的扭矩波动和在系统中引入的不对中(齿轮、轴和外壳组件之间)作为传动系的机械激励，导致齿轮啮合振荡和发出噪声(称为WINE NVH)。考虑到动力系统的大范围运行条件和高功率电机导致的励磁增加，这一问题变得更加复杂，这影响了机电耦合动态的稳定性。上述电动总成NVH的前景要求在同一框架下考虑各种相互关联的学科(电磁学、部件柔性、暂态动力学和噪声辐射)。一项旨在了解相关物理问题根本原因的耦合基础研究尚未成功完成。这项拟议的研究旨在找出电动汽车哨声和传动系统NVH行为耦合的根本原因，并开发新的设计解决方案，以降低其严重性，并避免在开发过程的后期采取昂贵而困难的NVH补救措施。该研究将通过以下方式从NVH的角度产生电子动力总成设计方面的基础知识：i)通过分析导致激进NVH行为的电子马达和传动系统瞬时动力学之间的耦合的根本原因，将为电子动力总成产生新的科学知识，ii)将开发用于高频(10 kHz以上)电子动力总成NVH研究的准确和有效的方法，Iii)新的NVH指标将用于未来的电子动力总成研究，以及iv)基于上述NVH指标和经过验证的3D电子动力总成模型的参数研究，将开发新的快速降阶方法。在参与的行业合作伙伴的大力支持下，本项目将开发新的电子动力总成设计方法，以实现快速和准确的产品开发。到达和AVL将在他们的设计流程和产品组合中整合新方法(在5年的时间范围内)。项目成果将在全国(和国际)传播，使英国汽车制造商能够直接受益，并保持其在动力总成技术方面的卓越。

The "Road to Zero" strategy is placing the UK at the forefront of designing and manufacturing zero emission vehicles, with the sale of new petrol/diesel cars and vans planned to end by 2040 (perhaps by 2030 according to recent government announcements). The strategy towards cleaner, quieter cities has accelerated the trend in the sales of Electric Vehicles (EVs). Contrary to the prevalent view though, EVs are not silent. Without the effect of masking noise from an internal combustion engine, other sounds radiating from the electric motor and the drivetrain have become more apparent (mainly at medium to high vehicle speeds). This is a major challenge for Automotive OEMs, which need to adapt their Noise, Vibration and Harshness (NVH) design methods to the "new" electric (e-) powertrain environment. Moreover, an optimum balance has to be identified between the vehicle NVH performance (and NVH package weight) and other weight increases due to heavy battery packs needed to increase the driving range.An important NVH issue in EVs is the tonal e-motor whistling noise (at harmonics of the rotor speed, depending on the number of motor poles). This is generated by the electromagnetic force, which excites the e-motor and the driveline housing. The noise is amplified by the powertrain structure, especially by the stator and its housing. Increased power and e-motor downsizing are key commercial requirements but have adverse effects on whistling noise. In addition to this, e-motor torque variation ripples and introduced misalignments in the system (between the gears, shafts and housing assembly) act as mechanical excitation on the drivetrain, leading to gear meshing oscillations and emitted noise (known as whine NVH). The issue becomes more complex considering the large range of powertrain operating conditions and increased excitation due to high-power motors, which affect the stability of the coupled electromechanical dynamics.The above e-powertrain NVH landscape requires various interrelated disciplines to be considered under the same framework (electromagnetics, component flexibility, transient dynamics and noise radiation). A coupled whistling and whining fundamental study that leads to root-cause understanding of the involved physics has not yet successfully done.The proposed research aims to identify the root causes behind the coupling of e-motor whistling and drivetrain whining NVH behaviour in e-powertrains and develop novel design solutions to reduce their severity and avoid costly and difficult remedial NVH measures later in the development process. The research will produce fundamental knowledge in e-powertrain design from the NVH perspective in the following ways: i) novel scientific knowledge will be generated for e-powertrains by analysing the root causes of the coupling between the e-motor and drivetrain transient dynamics that leads to aggressive NVH behaviour (employing 3D e-powertrain models), ii) an accurate and validated methodology for high frequency (above 10 kHz) e-powertrain NVH studies will be developed, iii) new NVH metrics will be set for use in future e-powertrain investigations and iv) novel and fast reduced-order methods will be developed based on the above NVH metrics and the parametric studies of the validated 3D e-powertrain models.New e-powertrain design methodologies for fast and accurate product development will be developed in this project with strong support of the participating industry partners. Arrival and AVL will integrate the new methods in their design processes and product portfolio (within a 5-year timescale). The project outcomes will be disseminated nationally (and internationally) so that UK automotive manufacturers can directly benefit and the UK maintains its excellence in powertrain technology.