Measurement Location Optimization of Component TPA Method for Road Noise

In this paper, an investigation on the application of a non-intrusive on-site component Transfer Path Analysis (TPA) method is presented together with the comparison with a previously performed direct blocked forces method. The latter is the more common method to determine interface forces between active and passive parts of an assembly. Force transducers are placed between the investigated structure and a rigid measurement rig. The presented comparison shows an investigated whether the faster and cheaper TPA method was able to produce relevant results. The TPA method used in this work calculated the force component contributions, without disassembly of the interfaces, through the local stiffness of multiple indicator positions per interface combined with operational measurement. The method is based on the application of an inverse-matrix model. This approach was applied to a vehicle road noise investigation carried out on a roller bench at three different roller speeds. A rough surface single axle roller bench in the same conditions as for the blocked forces method was used. The matrix inversion was carried out by using an overdetermined set of linear equations using an optimum number of degrees of freedom (DOFs) after post-investigation of the signals. The results were determined using different reference positions and compared to find the best procedure. This selection process will be discussed and found crucial to obtain relevant results. This paper shows the results for the wheel carrier loads and torques, using Virtual Point Transmissions of the indicator DOFs to the corresponding interface position. The comparison between the calculated and the measured direct forces showed very similar results and phenomena likely to appear in road noise excitation as component resonances and tyre cavity modes were clearly visible. The matrix inversion method is observed to be a useful alternative if indicator DOFs and reference point selection are performed with care.