Consideration and Verification of Accuracy Evaluation Indices for Operational TPA

Abstract

In this study, we considered accuracy evaluation indices for operational transfer path analysis (TPA) that employs the principal component regression method, and we verified their reliability. To evaluate the accuracy of TPA, the consistency of the response signals, in which the calculated response signal from the TPA model is compared with the measured response signal, has been frequently used in the past. Also, some cases use the condition number that indicates the inverse matrix condition used in the calculation procedure of the acceleration transfer function. In addition to these accuracy evaluation indices, a correlated principal component number (CPCN), which indicates the number of principal components that correlate with the response signal generated at the running test, has been proposed. The reliability of these accuracy evaluation indices has been verified through a simple simulation. The results show that the two conventional indices (the consistency method and the condition number) do not satisfactorily evaluate the accuracy. However, a CPCN can indicate the frequency bands where the TPA accuracy is high or low. Consequently, the new index was found to be a suitable index for evaluating the accuracy of the operational TPA.

Target Level Setting Method for the Reference Signal of Operational TPA

“…In the first step, the transfer function from the reference point to the response point is calculated using various operational data measured at the reference and response points. In the second step, each contribution is obtained by multiplying the reference point signal by the calculated transfer function (2), (12), (14) . The transfer function in this method is calculated using a principal component regression method.…”

“…Moreover, several orthogonal vibration modes, which are excited during operation, are included in the measured reference signals. Hence, an orthogonal principal component is considered to be the same as a vibration mode excited during operation (12), (14) . The target setting method using the principal component can obtain the target levels of reference signals considering the relationship among reference signals.…”

“…The principal component, which is obtained from the calculation procedure of the transfer function of the operational TPA using principal component regression, is expressed by reference signal [A in ] and transpose matrix [V], as shown in Eq. (14).…”

“…Each contribution is obtained by multiplying the individual input signals with the transfer function by the response signal, and several TPA methods have been proposed (1) - (14) . Operational TPA is a recently developed TPA method that enables the contributions to be obtained in a few man-hours because this method requires only sound pressure or vibration acceleration data during operation, and does not require an impulse hammering test in order to obtain transfer functions (2) .…”

“…Operational TPA is a recently developed TPA method that enables the contributions to be obtained in a few man-hours because this method requires only sound pressure or vibration acceleration data during operation, and does not require an impulse hammering test in order to obtain transfer functions (2) . A number of studies on operational TPA have examined theoretical verification and application examples in vehicle development (3) - (10) , as well as assessing the accuracy and possible improvement methods for such techniques (12), (14) .…”