F2008-12-152
Balancing Speed and Accuracy of Test Based NVH Troubleshooting Using an Advanced Path Contribution Method
15 years of NVH applications make Transfer Path Analysis (TPA) appear a commodity tool. But, despite the fact that TPA is today used in a large variety of applications, the method remains an expert methodology requiring insight in both the NVH problem and all the related signal and system analysis constraints. The main bottleneck of conventional TPA is the required test time to build the full data model.
Several new approaches have been developed over the past years that try to circumvent this limitation. One of the striking examples is the recently developed, fully-operational TPA approach, requiring only operational data measured at the path references (e.g. mount accelerations, pressures closeby vibrating surfaces, nozzles and apertures, etc.) and target locations. The key step in this method is the estimation of the transmissibility matrix from the operational data, characterizing the relation between the target responses and the path references. This fully-operational TPA method is indeed very time-efficient, but suffers from several weaknesses that lead, in many cases, to incorrect path contributions and wrong engineering decisions. Typical examples of weaknesses are (i) the well-known cross-coupling effects between the path references which lead to faulty interpretations, (ii) the contributions of forgotten paths that are distributed over the remaining paths and (iii) ill-conditioning problems leading to unreliable transmissibility estimates.
This paper first briefly reviews the past progress in TPA methodology and its limitations, with a main focus on the conventional full TPA approach and the fully-operational method. It then introduces an innovative approach addressing these limitations for airborne as well as structure borne problems. The new approach is based on simplifications that allow balancing path accuracy and speed of execution, which is typically the driving factor to explore new methodologies today. The principles of the new approach are first outlined. The method is then applied to an automotive customer problem and compared with the existing approaches, showing the advantages in real life.
Session: NVH