Cyclic frequency extraction method for characteristic components of transient conditions of gearbox

The invention discloses a cyclic frequency extraction method for the characteristic components of the transient conditions of a gearbox. The cyclic frequency extraction method comprises the steps of performing interpolation on the frequency curve of the characteristic components at an original sampling interval, performing fitting on the interpolated frequency curve to determine a linear frequency modulation base function within multiple scale intervals, calculating the projection coefficient of a vibration signal within each interval to the base function, searching for the projection coefficients scale by scale to determine a piecewise linear path and adaptively segmenting the vibration signal of which the frequency changes arbitrarily in the form of a curve into a plurality of signal segments which are different in scale and of which the frequencies change linearly according to the path, performing least square fitting on each segment of the frequency curve, determining and calculating the filter order of FRFT and a filter center parameter, orderly performing FRFT single-order filtering on each signal segment according to the parameter, and then orderly connecting the filtered signals, thereby realizing the cyclic frequency extraction of the characteristic components of which the frequencies change in the form of the curve. The method is capable of realizing adaptive cyclic frequency extraction of the characteristic components; other components and the noise interference can be effectively stripped in the extraction process; careful analysis is performed on the extracted characteristic components; as a result, the early-stage weak faults of the gearbox can be diagnosed more accurately.