Operational transfer path analysis of high frequency noise in electric vehicles: air-borne and structure-borne contributions from electric front and rear axle drive units
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Examensarbete för masterexamen
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Transfer Path Analysis (TPA) has been a major NVH refinement framework utilized
in the automotive industry for years. Traditionally, classical TPA has been used to
conduct Source-Path-Receiver based investigations. However, its time-consuming
nature and the inability to maintain complete vehicle boundary conditions limit its
application to vehicle development stages. Over the recent years, shorter vehicle
development cycles have led to the evolution of more practical TPA techniques.
Operational TPA (OTPA) is one such efficient and time-saving method, which even
ensures the maintenance of boundary conditions over the complete vehicle. However,
OTPA results are extremely sensitive to instrumentation and hence, it demands
greater care for the inclusion of all coherent transmission paths within the vehicle.
OTPA has been proven to be an efficient troubleshooting tool over the conventional
Internal Combustion Engine (ICE) vehicles. However, there still remains a vast
scope for its implementation in modern electric vehicles due to the high frequency
nature of their propulsion noise.
This Master Thesis deploys OTPA to study high frequency noise and vibration
propagation from the electric propulsion units inside a prototype Battery Electric
Vehicle (BEV). Upon a detailed inspection of the potential air-borne leakages and
structure-borne transfer paths from the electric motor bays into the vehicle, measurements
were conducted on a chassis dynamometer inside a semi-anechoic chamber.
Next, individual path transmissibilities to the response, i.e., the Driver Ear Level
(DEL), were estimated upon Cross-talk Cancellation (CTC) using Singular Value
Decomposition (SVD) and Principle Component Analysis (PCA), and a detailed
Path-Receiver based vehicle model was formulated. Moreover, the critical paths
responsible for high frequency noise propagation inside the vehicle were detected.
To conclude, validation studies were conducted in order to verify the estimated
path contributions. The investigation also revealed some challenges in frequency
distinction between the air-borne and structure-borne contributions.
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Operational Transfer Path Analysis, Path Contribution, Cross-talk Cancellation, Singular Value Decomposition, Principle Component Analysis, Order Analysis, Airborne, Structure-borne, Battery Electric Vehicle