tailieunhanh - Báo cáo hóa học: " Detecting Impulses in Mechanical Signals by Wavelets"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Detecting Impulses in Mechanical Signals by Wavelets | EURASIP Journal on Applied Signal Processing 2004 8 1156-1162 2004 Hindawi Publishing Corporation Detecting Impulses in Mechanical Signals by Wavelets . Yang Institute of Vibration Engineering Northwestern Polytechnical University Xi an 710072 China Email . Ren Institute of Vibration Engineering Northwestern Polytechnical University Xi an 710072 China Email renxmin@ Received 21 February 2003 Revised 17 October 2003 Recommended for Publication by Marc Moonen The presence of periodical or nonperiodical impulses in vibration signals often indicates the occurrence of machine faults. This knowledge is applied to the fault diagnosis of such machines as engines gearboxes rolling element bearings and so on. The development of an effective impulse detection technique is necessary and significant for evaluating the working condition of these machines diagnosing their malfunctions and keeping them running normally over prolong periods. With the aid of wavelet transforms a wavelet-based envelope analysis method is proposed. In order to suppress any undesired information and highlight the features of interest an improved soft threshold method has been designed so that the inspected signal is analyzed in a more exact way. Furthermore an impulse detection technique is developed based on the aforementioned methods. The effectiveness of the proposed technique on the extraction of impulsive features of mechanical signals has been proved by both simulated and practical experiments. Keywords and phrases wavelet transform envelope analysis fault diagnosis rolling element bearing soft threshold. 1. INTRODUCTION The extraction of impulsive features in vibration signals is vital for diagnosing such machines as engines rolling element bearings gearboxes and so on. Researchers have developed many methods for fulfilling this purpose for example cepstrum analysis 1 signal demodulation procedure 2 transmission error measurement 3 higher-order .