Random vibration testing with kurtosis control by IFFT phase manipulation
Non-Gaussian random shaker testing with kurtosis control is introduced in the paper as a way of increasing or decreasing the excitation crest factor (CF). The CF increase is required for more accurate simulation of ground vehicle vibrations and the CF decrease is useful in other applications such as modal testing. Using kurtosis as a measure of CF behavior leads to closed-form solution for making the IFFT generation non-Gaussian by special phase manipulation. A universal phase selection procedure capable of modeling random excitations with a high or low kurtosis has been developed. Because of the analytical solution advantage, the proposed phase method meets time restrictions critical for shaker controller operation. Low CF values achieved by the suggested analytical kurtosis-based solution are close enough to those obtained by the known method of sequential moment minimization, which considers moments of higher order but by numerical optimization only. In the case of CF increase, the developed phase manipulation algorithm randomizes high peaks in terms of their amplitude, position, and the number of severe peaks per data block. This ensures realistic variability of high peak behavior distinct from having just one high peak of narrow height variation in all data blocks as in another known approach of on-band phase limiting that is also a numerical technique, not an analytical solution as the proposed method.
kurtosis ifft phases non-gaussian random shaker testing crest factor