DEVELOPMENT AND ANALYSIS OF TIME VARIANT DISCRETE FOURIER TRANSFORM ORDER TRACKING

Several of the common order tracking methods for solving noise and vibration problems of rotating machinery are reviewed. These methods include the fast Fourier transform (FFT) and resampling based order tracking algorithms. The time variant discrete Fourier transform (TVDFT) is developed as a new and alternative order tracking method. This method contains many advantages which the current order tracking methods do not possess. The TVDFT has the advantage of being very computationally efficient as well as the ability to minimise leakage errors. The basic TVDFT method may also be extended to a more complex method through the use of an orthogonality compensation matrix which can separate closely spaced orders as well as separate the contributions of crossing orders. The basic TVDFT is a combination of the FFT and the resampling based methods, a special case of the chirp-z transform. This method can be formulated in several different manners, one of which will give results matching the resampling based methods very closely. Both analytical and experimental data are used to establish the behavioural characteristics of this new method.