Abstract
Hybrid and Electric Vehicles (HEV and EV) have rapidly become part of the standard vehicle portfolio for the global automotive companies. Optimizing their NVH performance is a task which commonly carries three main themes; this paper aims to provide answers to the key questions in these themes.
Firstly to optimize the powertrain noise at source, not just for quietness but to give the correct sensations to the driver. As the core part of the drive system is an electrical device the influence of controls and electronics on the noise generated are equally important as the mechanical elements. The study investigates how to analyze this coupled source effectively.
Secondly, the vibro-acoustic connections between the powertrain and driver comprise the complex combination of powertrain mount, powertrain surface, vehicle body, trim and fluid (air). Transfer Path Analysis (TPA) has long been a technique applied to give an insight into the sensitivity of connections between powertrain, body and driver for accurate route cause of unwanted noise. Its applicability to EV is investigated in this paper as reduced forcing functions from the electric motor (compared to the combustion engine) and the wider frequency range of interest (0-8000Hz) are thought to be major challenges to obtaining clear results with this method
Thirdly and finally, how to consolidate these results with the receiver’s perception of the sound? Subjectively electric vehicles provoke a mixed response, a significantly different feel to a combustion engine vehicle. How does this different source and transfer path matrix combine to give benefits and importantly where does it provide opportunities for improvement? Results of the above project are used to show how manufacturers can take this in to account in their vehicles.
KEYWORDS – Finite Element Analysis, Transfer Path Analysis, Electric Vehicle, Warning Sound, Acoustic Optimization,