An embedded sensitivity approach for diagnosing system-level vibration problems

Abstract In diagnosing a system-level vibration problem, the goals are to identify which component or components(s) are most responsible for the phenomenon and which changes to the system are most likely to mitigate the problem. The use of sensitivity analysis in diagnosing system-level vibration phenomena is examined in this work. It is shown that even if only a small subset of measured system input–output functions is available, an appropriate analytical parameterization of these functions leads to simple relationships between the measured data and the desired embedded sensitivity functions. These functions are then reformulated in terms of transmissibility functions with respect to a single input using a novel modal deflection chain technique in order to accommodate system-level operating response data in the absence of input measurements. The embedded sensitivity approach is used to examine two competing design modifications for reducing a structure-borne noise problem in an exhaust system. The sensitivity analysis shows that although both modifications mitigate the resonant vibration problem of interest, one of the modifications is more effective than the other because it introduces less overall change in the forced response characteristics at other frequencies.