The modern, ever shorter development process of powertrains incorporates many disciplines of mechanical engineering. Among these, the dynamic and acoustic behavior—which is often referred to as noise, vibration, harshness (NVH)—is becoming increasingly important for the consumer’s purchase decision. However, NVH is often only considered in the last steps of the product development as both experimental analysis methods and high-fidelity modeling approaches are time-consuming. In contrast, in early phases of the development process, fast iteration cycles are crucial. Thus, the engineer needs appropriate NVH models for each phase of the development process in order to evaluate design and concept decisions with respect to their NVH implications.This publication shows a methodological guide on how to apply suitable NVH models forward directed in different stages of the development process and thus efficiently implement optimizations. In the early, highly iterative phases of the development process, analytical determination of the excitation behavior as well as simplified finite element simulations are carried out in order to estimate the vibration behavior of the concept. For the first elaborated geometries, frequency response functions can then be determined and thus the influence of e.g. ribbings to NVH behavior can be evaluated. In the later phases, where advanced simulation models have to be set up, a fully parameterized eMBS model of the drivetrain enables an analysis of its operating behavior, from which further optimization potential of the system can be derived. The proposed method is demonstrated on the example of a tractor transaxle development process.

In comparison to internal combustion engines, which usually have low frequency, broadband excitations, in electric vehicles, tonal excitations from the electric drivetrain are noticeable and disturbing. As the acoustic and structural dynamic behavior, often referred to as noise, vibration, and harshness (NVH), strongly influences customers’ quality perceptions, optimizing it is a key challenge in development. This study investigates the influence of static rotor–stator eccentricity on the NVH behavior of an electric drivetrain using a transient elastic multibody simulation (eMBS) model incorporating non-linear gear meshing, bearing contact, and electromagnetic forces. The analysis identifies the 36th order excitation of the electric machine as the dominant source, leading to a maximum total acceleration level of 152 dB. Two specific excitation directions were found to reduce this amplitude most effectively. However, varying the amount of static eccentricity in these directions resulted in only minor vibration reductions (<1.5 dB). The findings indicate that the symmetric mode shapes of the cylindrical housing govern the response, indicating that addressing the excitability of housing modes by developing asymmetric housing designs could offer a more effective approach for NVH optimizations of electric drivetrains.

In electrified vehicles, the masking noise behavior of internal combustion engines is absent, making the tonal excitation of the electric machine particularly noticeable in vehicle acoustics, which is perceived as disturbing by consumers. Due to manufacturing tolerances, the tonal NVH characteristics of the electric machine are significantly influenced at wide frequency ranges. This paper presents a systematic exploration of the influence of static eccentricity as one manufacturing tolerance on the NVH behavior of Permanent Magnet Synchronous Machines (PMSMs). The study utilizes a novel test bench setup enabling isolated variations in static eccentricity of up to 0.2 mm in one PMSM. Comparative analysis of acceleration signals reveals significant variations in the dominance of excitation orders with different eccentricity states, impacting critical operating points and dominant frequency rages of the electric machine. Despite experimentation, no linear correlation is observed between increased eccentricity and changes in acceleration behavior. Manufacturing eccentricity and deviations in rotor magnetization are discussed as potential contributors to the observed effects. The findings emphasize static eccentricity as a critical parameter in NVH optimization, particularly in electrified powertrains. However, the results indicate that further investigations are needed to explore the influence of eccentricities and magnetization deviations on NVH behavior comprehensively.

The modern, ever shorter development process of electrified drivetrains requires methods that enable a sufficiently fast acoustic evaluation of design decisions. The dynamic and acoustic behavior (NVH) forms a crucial aspect for the consumer’s purchase decision. Since experimental and empiric optimization approaches are highly inefficient, simulation methods such as the elastic multi-body simulation (eMBS) are used to sufficiently simulated the NVH-behavior of the drivetrain by performing transient run-up simulations. However, these simulations are highly computationally intensive, leading to computational times of multiple days or weeks, thus making those optimization approaches inefficient during iterative phases of the development process. Therefore, there is a need to reduce the overall simulation time for eMBS-based evaluation of design decisions. This publication proposes a method on how to parallelize transient runup simulations to significantly decrease the needed simulation time for eMBS simulations. In this process, a partition of the time domain is achieved by analytically calculating the kinematic states of individual components at discrete time steps. As a result, a multitude of runup partitions can be computed in parallel, leading to a drastic reduction in simulation time. This method is demonstrated by examining an electrified powertrain. The application of the method shows a reduction in simulation time for a transient drivetrain runup of over 90%. The validation is carried out by comparing the parallelized computational results to a conventional transient simulation of the electrified drivetrain. Based on the proposed method the engineer is capable to efficiently use detailed eMBS system models within highly iterative phases of a development process for the evaluation of design decisions and therefore address NVH-optimizations more sufficiently.