RANDOM EXCITATION FOR MODAL TESTING OF ROTATING MACHINERY: USE OF MODULATION TECHNIQUE

One of the most popular excitation methods for modal testing of rotating machinery is known to be the uncorrelated isotropic excitation, which requires two independent random sources with equal power for generation of a pair of uncorrelated excitation signals. In this work, a new excitation method, the modulated random excitation, is proposed such that a pair of random signals with equal power for modal testing of anisotropic rotors can be effectively generated by modulating the random signal from a single random source with two harmonic carriers of a frequency with 90° phase difference. The real as well as complex approaches are taken to illustrate the effectiveness of the modulation technique. Finally, digital data processing technique is discussed in relation to the implementation of the modulation technique in the discrete time domain.