Development of an Analytical Method for Rear Differential Gear Whine Noise utilizing Principal Component Contribution by OTPA and CAE 2019-01-1555
Due to the global warming concern, CO2 emission regulations have been reinforced in most countries and electrification of automobiles has accelerated. Since the engine noise will be largely reduced, the improvements of gear whine noise becomes more important. But gear whine noise mechanism is complicated by involving many parts and transmitting paths to the cabin. Operational Transfer Path Analysis (OTPA) is one of the TPA methods to determine the main path and contributing part using only the operational data. However, in cases which many reference points are set on the same frame or body, the contribution becomes similar by high correlation among the reference data set and finding out the main transfer part becomes difficult. The contribution of principal component (PC) which is obtained from the correlated reference signals, instead of calculating the contribution from each reference point by modifying the OTPA process, has been utilized. Through this process, important vibration behavior of the target structure can be obtained as the high contributing PC mode. In this paper, this approach was applied to vehicle and verified. In addition, for applying the method, enormous signals at the reference and response points are necessary to be recorded simultaneously. This issue makes the method difficult to be applied especially to the high frequency phenomenon. This issue was solved by using frequency responses calculated from FEM models which were converted to transient data by inverse FFT. After obtaining sufficient numbers of data by the simulation, the data were used to identify the high contributing PC modes and the vibration modes. Using these findings the vehicle was modified and the vibrational and sound pressure levels were confirmed to decrease and the effectiveness of the developed method was verified.
Miho Nakatsuka, Tetsuya Miwa, Junji Yoshida
Toyota Motor Corporation, Osaka Institute of Technology
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