NVH refinement is an important aspect of the powertrain development and vehicle integration process. The depletion of fossil-based fuels and increase in price of gasoline have prompted most vehicle manufacturers to embrace propulsion technologies with varying degrees and types of hybridization. Many different hybrid vehicle systems are either on the market, or under development, even up to all-electric vehicles. Each hybrid vehicle configuration brings unique NVH challenges that result from a variety of sources. This paper begins with an introductory discussion of hybrid propulsion technologies and associated unique vehicle NVH challenges inherent in the operation of such hybrid vehicles.
Following this, the paper outlines a two-dimensional landscape of typical customer vehicle maneuvers mapped against hybrid electric vehicle (HEV) operational modes. Overlaid on this map are NVH issues such as those associated with global powertrain vibration, driveline vibration, HEV component-specific noise, motor/generator whine, accessory noise, gear rattle, and noise pattern changes. The remainder of the paper focuses on specific examples from case studies illustrating key HEV NVH issues such as engine start/stop behavior, motor/generator whine, and influence of electric machines on powerplant integration issues. The use of advanced time-domain methods such as vehicle interior noise simulation (VINS) to understand and optimize HEV vehicle NVH behavior is shown. Finally, the findings from the discussed studies are summarized and appropriate conclusions are drawn with respect to understanding, characterizing, and solving unique hybrid vehicle NVH issues.
