关键词: 系统辨识, 分数阶系统, 小波分析, 降噪, 阈值, 变尺度

Abstract: The identification theory and method of fractional system is an important research direction which has drawn much research attention recently, and how to reduce the noise about the identification test data is one of the subjects which must be focused on. In this paper, on the basis of wavelet theory and method, the characteristics of noise and output signal of fractional system were analyzed firstly. In order to overcome the limitations of the conventional threshold denoise method, a nonlinear variable metric algorithm for the multilevel wavelet decomposition coefficient was proposed, and then a denoising method for identification signal of fractional system was formed. The simulation experiments indicate that this method can reduce the noise to a satisfactory level, and it also has good adaptability for different Signal-to-Noise Ratio (SNR) cases. Our research purpose is to provide a reference for further identification algorithm design and to improve identification precision.

Key words: system identification, fractional system, wavelet analysis, denoising, threshold, variable metric