Estimation of Frequency Response Function on Rotational Degrees of Freedom of Structures. 2nd Report. Improvement of Accuracy for Random Noise.

Experimental modal analysis is a fundamental technique for the analysis of structural vibration. However FRF measurement on rotational degrees of freedom (DOFs) has been disregarded in the experiment because of the difficulties of measurements. Rotational FRFs are vital to extend the applicability of experimental modal analysis. The authors have proposed a measurement technique of rotational FRFs. It is important to evaluate the accuracy and reliability of estimated rotational FRFs. In this paper an improved method for the estimation of rotational FRF and the evaluation fuction of the reliability of rotational FRF are presented: The variance of rotational FRF is derived by considering the propagation of random noise in the measured FRF; and the Reliability Factor of estimated FRF is also obtained from variance. The effect of random noise in the measurement to the rotational FRF is investigated by numerical simulation and experimental application.