The nonlinear frequency spectrum model of servo motor of large-scale numerical control equipment transmission
system is established based on nonlinear frequency spectrum analysis method of Volterra series. The frequency spectrum
feature of two parametric type faults of transmission system is analyzed. An usable online frequency spectrum feature
extraction and fault diagnosis method is proposed. The method uses adaptive identification algorithm to solve domain Volterra
kernel and adopts fast multi-dimensional Fourier transform to extract nonlinear frequency spectrum feature. Experimental
result shows that the proposed method has good timeliness and high recognition rate for equipment fault.