Analytical Tool for Design & Optimization of Double Isolation Mounting System for Electric Powertrain

As the world rapidly moves from IC engine powered vehicles to the ‘more sustainable’ electrified vehicles, the Powertrain Mounting System needs to be re-engineered to meet refinement requirements of customer. Electric vehicles are quieter but due to lack of the “masking effect”, are sensitive to minor disturbances that are perceived to be objectionable by passengers. Also, E-powertrains are lighter, produce higher torque at low rpms & operate at higher rpms which calls for different countermeasures for mounting systems compared to conventional single isolation 3-point mounting system as used in IC engines. Double isolation mounting system, where powertrain is connected to an auxiliary mass (sub frame/cradle) via mounts, which is suspended to the vehicle body via subframe bushes results in 12 rigid body modes, 6 for each mass, is highly effective in lowering the transmission of vibration at high frequencies. This paper discusses 12 DOF analytical tool developed to rapidly analyze the powertrain double isolation mounting system rigid body modes as well as kinetic energy distribution and decoupling. Results are compared with actual measured values as well as with commercially available Simcenter Amesim simulation tool and good correlation is established. Based on the developed tool, parametric study on number of mountings, stiffness and location sensitivity is studied and optimum e-powertrain mounting system is designed meeting modal & system deflection targets which is validated in test measurement.