Elimination of transducer mass loading effects in shaker modal testing

Abstract

In modal testing, some sensors having to be mounted on the test structure will introduce extra mass loading to the system and then adversely affect the measured Frequency Response Functions (FRFs). This paper deals with elimination of accelerometer and force transducer mass loading effects from measured FRFs (including point FRF and transfer FRF) in shaker modal testing. Considering different sensors for response measurements, two common collocations in shaker modal testing are investigated: (1) shaker+Laser Doppler vibrometer case in which only force transducer mass loading effects need to be removed, and (2) shaker+accelerometer case in which both accelerometer and force transducer mass should be eliminated. The correction method employed for case (1) is theoretically deduced and it demonstrates a good performance in experimental validation. Two correction methods are proposed for case (2) and the numerical simulation shows that one of them is effective with certain degree noisy data, however, another is vulnerable to the noise. The main reason for the sensitivity of the method to noise is analyzed and further work is necessary in order to solve this difficulty.