Motor square current signature analysis for induction motor rotor diagnosis

Induction machines play an important role in today’s industry. Thus, preventive maintenance combined with fault diagnosis techniques have become an essential issue. One of the most used techniques for the diagnosis of faults in the induction machine is motor current signature analysis (MCSA). This approach presents some limitations for induction motor rotor diagnosis, particularly for small faults. In this paper, a new motor square current signature analysis (MSCSA) fault diagnosis methodology is presented. The proposed technique is based on three main steps: first, the induction motor current is measured; secondly, the square of the current is computed; and finally a frequency analysis of the square current is performed. This technique allows more information to be obtained from a motor with a rotor fault than the classical MCSA approach. Simulation and experimental results are presented in order to confirm the theoretical assumptions. This methodology has also been tested for the identification of two distinct faults (broken bars and rotor eccentricity).     

基于滤波器组的高效信道技术

随着新型低截获雷达信号的出现,雷达接收机带宽越来越宽,宽带数字接收机成为了通信、雷达及电子侦察领域的研究热点.作为众多宽带数字接收机之一,数字信道化接收机以其全概率接收和同时处理多个信号的特点成为了研究重点.本文对数字信道化技术和数字采样理论进行了研究,推导得到了一种基于滤波器组的高效信道化模型,计算机仿真结果验证了该模型的正确性.该高效信道化模型相对传统的模型具有较低的计算复杂度,适用于工程应用.     

An algorithm for improving the coefficient accuracy of wavelet packet analysis

On the basis of analyzing the cause of coefficients distortion inhered in the existing wavelet packet transform algorithms, a new method is presented to rectify the distortion and improve the accuracy. Its principle is to implement compensation calculation by using the complementary characteristic of wavelet filters. The simulation result of a typical signal shows the method is effective in improving the accuracy of wavelet packet coefficients. The influences of the compensation calculation times and vanishing moments of the wavelet are analyzed. Theoretically, the maximum error could be reduced to 25% with one time compensation calculation. The results show that with two and four times compensation calculations, the error is reduced to 10% and 2% respectively. The experiment result of the vibration signal of a roller bearing with outer ring fault shows that the proposed method can effectively magnify the amplitude of the fault frequencies in practice.