【作者】 周郁明；

【导师】 李佐宜； 杨晓非；

【作者基本信息】 华中科技大学 ， 微电子学与固体电子学， 2004， 硕士

【摘要】 钢丝绳是一种应用广泛的挠性构件。但是,经过使用后的钢丝绳中不可避免存在断丝等缺陷,如果不及时发现,往往会带来严重的后果。由于使用中的钢丝绳断裂往往是由少量断丝引发的大量集中断丝所造成的,因此,早期及时发现钢丝绳的少量断丝,对于钢丝绳的断丝检测具有重要意义。而少量断丝产生的漏磁场往往很微弱,因此,必须选用灵敏度高、性能良好的传感器来拾取断丝信号,并能正确处理断丝信号,这对于钢丝绳的断丝检测有重要意义。本文将就这些技术问题进行探讨和研究。在研究中,比较了几种常用的磁敏感元件的特性,结合钢丝绳断丝信号弱的特点,选用了综合性能良好的磁阻传感器,并设计了传感器的激励电路。由于磁阻传感器有一定的测量范围,在不失一般性的情况下,运用电磁场的有限单元法计算了钢丝绳在几种断丝情况下产生的漏磁场,并描述了漏磁场的分布特征,为检测系统的设计提供理论依据。由于钢丝绳断丝漏磁场强度较弱,传感器输出信号的信噪比低,断丝信号难以观察,因此在故障模式识别之前,必须进行信号预处理,作者设计了钢丝绳断丝信号放大电路。同时,在实验室的环境下,研究了信号中噪音的来源,根据噪音的频谱,设计了信号滤波电路。在研究断丝信号的软件处理时,对比了傅立叶变换和小波变换在信号处理方面的特点,然后将断丝信号进行小波三层分解,根据噪音特性保留第三层的低频部分作为重构信号,并运用平滑处理的方法从重构信号中完整地提取出断丝信号。最后选取经过处理后信号的绝对峰值、峰峰值等几个特征量作为BP神经网络的输入,对钢丝绳的断丝进行定量识别。更多还原

【Abstract】 As a kind of flexibility component, the wire ropes are applied widely. However, after used for a period, it is inevitable that some wire ropes may break. If the broken wires are not found out timely, severe affairs maybe happen. The reason that the wire ropes break in using is often that few broken wires product a mass of concentrative broken wires. Thus, finding out the broken wires early is very important to wire ropes’ inspection. However, the resulted magnetic flux leakage is so weak that highly sensitive and well performing sensor should be adopted, and the signals produced by the broken wires must be processed precisely. These steps are of great importance to the wire ropes’inspection. In this paper, these technical problems are discussed and researched.In this research, the characteristic of several magnetic field sensors is compared. In view of the fact that the signal of broken wires is very weak, the magnetoresistive sensor that has very fine performance synthetically is chose, at the same time a stimulating circuit is designed. Taking into consideration of the inspection range of magnetoresistive sensor, under the status of universality, the magnetic leakage flux of the broken ropes is computed with the electromagnetic finite element method, and the characteristic of the magnetic leakage flux is described. The result can be used as the theoretical basis of magnetic testing system.Because the intensity of magnetic leakage flux of broken ropes is very weak,the output voltage of magnetoresistive sensor is very low, thus making it very difficult to discover the broken wires. Consequently, before the broken wires are recognized the output signal should to be amplified. In this sense, the amplifying circuit for the signal of broken wires is designed. Under the condition of laboratory, the source of noises in the signal is researched. According to the frequency spectrum, a filter is designed. How to process the signal is discussed with software, and the Fourier Transform and Wavelet Transform are compared, then the signal is decomposed to the third layer with Wavelet Transform. According to the characteristics of noise, low frequency part of the third layer is kept as the reconstructed <WP=5>signal, and the perfect signal of broken ropes is obtained fully with the method of smoothness processing. At the last, the absolute peak value and peak-peak value of the processed signal are selected as the input of BP neural network, and are used to recognize quantitatively the broken wires of wire ropes.更多还原