Mounting Systems for Electric Powertrains: Optimization and Parameter Sensitivity

Abstract Noise, vibration, and harshness (NVH) characteristics of electric powertrains have been receiving increasing attention due to the unique vibroacoustic characteristics of different electric motors commonly used in electric and hybrid vehicles. NVH characteristics of electric powertrains are unique due to several reasons including harmonics of electromagnetic forces, coupling of modes of the motor stator assembly, noise and vibration resulting from pulse width modulation, etc. While a traditional mounting system for an internal combustion engine typically needs to be designed for a frequency range of 0 to 200 Hz, the response of an electric powertrain is generally expected to exceed 2 kHz. Therefore, factors such as internal resonance, wave effects, and high-frequency noise and vibration are specifically unique to electric powertrains and their mounting systems. Two engine mounting configurations that have shown promising results for electric powertrains are the cradle mounting system (three-point mounting) and the saddle mounting system (four-point mounting). These two mounting systems provide a balance between mitigation of force transmissibility at lower and higher frequencies while being well-suited for transient loads. This paper investigates the sensitivity of force transmissibility and frequency response to some of the design parameters of the engine mounting systems for electric powertrains. The determination of optimal mounting system parameters is also investigated in this study. A spatial model with a discretized representation of each engine mount has been used for analysis since it is capable of capturing wave effects as well as high-frequency responses up to 10 kHz. Results indicate that the model can be used to determine an optimal configuration of the mounting system especially when a specific frequency bandwidth is targeted. The optimal four-mount system is seen to substantially reduce the overall force transmissibility. The viscoelastic parameters and the mass and inertia of the powertrain are not seen to influence the peak amplitudes of force transmissibility while slightly shifting the natural frequencies of the lower modes without influencing higher modes. The results of this study can be used for the design and development of robust mounting systems for electric powertrains while accounting for design constraints.