Applications of Strain Measurements to Improve Results on Transfer Path Analysis 2019-36-0323

Vehicles with lower noise levels and better levels of vibratory comfort for passengers made the area of noise, vibration and harshness (NVH) one of the main areas related to the perception of vehicle quality. Several approaches on the contribution of transfer paths have been studied to define the propagation energy in vehicular structures. Transfer Path Analysis (TPA) is a tool to improve NVH performance with the primary goal of reducing and improving perceived vibrations and noise in the cabin vehicle by occupants. Indirect methods are especially important in cases where the force signals are immeasurable in practice in terms of cost and space for sensor couplings, in the measurement configuration, and particularly in the case of distributed forces. The matrix inversion method, perhaps the most popular classic TPA, identifies operational forces using passive body acceleration. However, removal of the source can change the dynamic characteristics of the assembled structure and increase the time of the experiment, which results in misleading information in the measurements. For this reason, the inversion operation of the acceleration matrix can give erroneous results, where the condition number of the inverted matrix gains considerably high values, especially in the resonant frequencies. Thus, this paper proposes the comparative study of force estimation techniques and transfer paths, based on the matrix inversion method with and without the application of strain techniques and compares with the computational model of the system. In order to carry out this work, an academic test bench simulating a vehicular powertrain was used. The results showed a good compromise between forces and transfer paths and a significant improvement in some frequencies using sensor fusion techniques.