Entropy 2015 17 7076-7086 doi:10.3390/e17107076 OPEN ACCESS...

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Entropy 2015 , 17 , 7076-7086; doi:10.3390/e17107076 entropy ISSN 1099-4300 www.mdpi.com/journal/entropy Article A Vibration Analysis Based on Wavelet Entropy Method of a Scroll Compressor Tao Liu * and Zaixin Wu School of Mechanical and Electronical Engineering, Lanzhou University of Technology, Lanzhou 730050, China; E-Mail: [email protected] * Author to whom correspondence should be addressed; E-Mail: [email protected]; Tel.: +86-931-2973860; Fax: +86-931-2757293. Academic Editor: Raúl Alcaraz Martínez Received: 30 May 2015 / Accepted: 10 October 2015 / Published: 19 October 2015 Abstract: Vibration-based condition monitoring and fault diagnosis is an effective approach to maintain the reliable operation of a scroll compressor. Unfortunately, the vibration signal from the scroll compressor always has characteristics of being non-linear and non-stationary, which makes vibration signal analysis and fault feature extraction very difficult. To extract the significant fault features, a vibration analysis method based on Wavelet entropy is proposed in this paper. Two forms of the wavelet entropy, namely the wavelet space feature spectrum entropy (WSFSE) and the wavelet energy spectrum entropy (WESE), are defined to depict instantaneous characteristics of the local variation of the vibration signal. Four types of mechanical faulty vibration signal, namely unbalanced rotor, malfunctioning scroll, loosened mechanical assembly, and loosened bearing, are analyzed by using the proposed approach. The experimental results show that feature components and energy distribution of each fault signal is accurately identified and revealed, which proves that the combined application of WSFSE and WESE approach is a successful scheme for the vibration analysis of scroll compressors. Keywords: vibration analysis; fault feature extraction; wavelet entropy; feature component; scroll compressor OPEN ACCESS
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Entropy 2015 , 17 7077 1. Introduction Scroll compressors have been becoming popular in refrigeration and air conditioning products because of their high efficiency, low noise, fewer components, low vibration, light weight, and small size compared with other types of compressors [1–5]. The malfunctions or faults because of the damages of their key components, such as fixed and orbiting scrolls, during the operating process of scroll compressors may cause abnormal operation and, if not detected early, can cause emergency shutdown. Therefore, efficient and accurate fault diagnosis technique is very important for guaranteeing reliability and performance of a scroll compressor. Over the past two decades, a large number of methods have been proposed for fault detection and diagnosis, and many attractive research results [6–14] have been obtained. In these methods, vibration-based spectrum analysis to the vibration signals of scroll compressors has been used as a regular technique in recent years [14–16] because of its capability of extracting fault feature from the signals. However, there still are some disadvantages in condition monitoring and fault diagnosis of scroll compressors. These deficiencies lead to some troublesome
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