Improved discrete Fourier transform algorithm for harmonic analysis of rotor system

Harmonic components are critically important to the fault diagnosis of rotor system. Various methods have been developed for harmonic component extraction. The challenge however, is to efficiently and accurately extract rotor system harmonic components. In this paper, a new harmonic analysis approach based on an improved discrete Fourier transform algorithm is proposed. It schemes out harmonic analysis sampling and resampling method to obtain synchronous sampling data, which can realize integer-period synchronous sampling and greatly increase the measurement accuracy of harmonic parameters. Then an improved discrete Fourier transform algorithm is proposed to extract harmonic components, which can dramatically reduce the computation load through replacing multiplication by shift operation. Finally, the effectiveness of the proposed method is analyzed by means of simulation and practical experiment for multifrequency simulated signal and shaft misalignment faults, respectively. Results show that the proposed method is faster and more accurate than both the DFT-based methods and the FFT-based methods for extracting harmonic components of rotor system.