teleporter振动检测仪中自由衰减振动信号频谱校正的研究
重庆大学硕士学位论文
学生姓名：***
指导教师：蔡坤宝教授
confidentiality刘晓明教授
专业：信号与信息处理
学科门类：工学
重庆大学通信工程学院
二O一O年四月
Rearch on Spectrum Correction of the Free Decaying Vibration Signals
2015年考研国家线in Vibration Detector
A Thesis Submitted to Chongqing University
in Partial Fulfillment of the Requirement for the
Degree of Master of Engineering
By
Li Baohuan
Supervid by Prof. Cai Kunbao
Liu Xiaoming Major:Signal and Information Processingcrayon的音标
College of Communication Engineering
Chongqing University, Chongqing, China
英语 单词
April 2010
英语美文欣赏
introduce mylf摘要
无损检测是工业发展必不可少的有效工具，随着无损检测技术应用与推广，其中振动信号分析法是当
前应用最广泛的技术之一，可以用于机械设备故障检测、电子对抗、图像处理等许多领域的生产实践中。
本文在认真学习和深入分析数字信号处理器（DSP）的理论基础上，对以DSP 为核心的振动探伤仪提出了一种新的改进方案。首先，基于振动探伤仪的实时性要求，本文提出利用CCS2.2（Code Compor Studio）自带的DSPLIB库中的FFT 函数对接收到的信号进行傅里叶变换处理。由于DSPLIB库是优化后的汇编程序，C语言对其可调用编程，且其兼容性强、计算速度快，要比单纯的C语言程序或单纯的汇编好的多，这就提高了振动探伤仪的灵敏性。系统用液晶显示器作为人机交换的平台，提供了良好的界面，与键盘和光电旋钮配合使用，使系统更便于操作与控制。
由于频谱泄露与栅栏效应引起频谱幅值的失真，本文在分析加窗后信号频谱产生的幅值误差的基础上，依据各窗函数的幅值恢.复系数的原则，系统地比较了四种窗函数的幅值误差，本文利用双窗函数法及幅值恢复法来改善频谱的幅值。由于实际工程应用不可避免地对信号产生干扰，本文利用小波包对自由衰减振动信号消噪，由仿真结果可以看出，小波包消噪效果很明显。
由于自由衰减振动信号是具有连续频率成分的信号，而目前对这类信号频谱校正研究还不深入。为了提高振动探伤仪的频谱估计的精度，在分析频谱细化的基础上，本文提出一种对自由衰减振动信号的频率进行估计的方法：先对信号进行FFT变换，并对信号频谱的峰值定位；然后，借助峰值及其临近
的、且取得极大值的3个频率点上的频谱数值，利用高斯拟合法来逼近这4个点上的谱线真值，由此得到拟合曲线的参数，找出更为精确的峰值，利用两次拟合得到的曲线峰值计算阻尼比。仿真分析及工程试验结果都表明该方法可以有效地提高检测精度，而且计算量相对较小。
关键词：FFT，频谱校正，自由衰减振动，高斯拟合，数字信号处理函数库
com sticktoitABSTRACT
Nondestructive testing is esntial tool of industrial development,with the application and promotion of nondestructive testing technology,the vibration signal analysis is one of the most widely applied technology,using in fault detection of mechanical equipment, anti-electronic, image processing and so on.
In this paper, a new improvement plan with DSP core is prented On the basis of careful study and analysis of the signal processor.First of all,this paper process received signals to fast Fourier Transformation by DSP library of CCS2.2.Becau DSPLIB is optimized asmbler, fast calculation, strong compatibility,and it is called and programmed by C language ,so this improve the nsitivity of the vibration detector.the system with LCD monitor as a man-machine exchange platform ,provides a good interface,cooperating with keyboard and opto-electrical knob, make the system more easy to o
id是什么意思
hummerperate and control.
In the ca that fence effect and specrum leak changed the amplitude spectrum,bad on an investigation of the amplitude errors in fourier transform and spectrum analysis produced by windowing, and according of the principle of the amplitude restored coefficient of the window functions,this paper systematically compared the error of the amplitude of four window functions, this paper improve spectrum amplitude by using a dual window function method and amplitude restoration method.due to inevitably interfere with singal in enngieering application,this paper make u of wavelet packet denoising to damped free vibration signal, simulation results show that the effect of wavelet packet denoising is obvious.
Becau the damped free vibration signal is continuous frequency component of signal,but the study of spectrum correction to that is not deep at the moment. In order to improve the frequency resolution of vibration detector,a new method which can correct the frequency of damped free vibration has been propod in this paper.Firstly, we arch for the peak value of signal spectrum, and using the peak value and three maximum points near it approximate the spectrum line compod by tho four points, then calculate the parameter of fitting curve. Secondly, we get the derivation of fitting curve, and find out the specific peak value. At last, we calculate the damping ratio
by
using the peak value from the two above fitting curves. Simulations and experimental results show that the new method will effectively improve the accuracy of detections, and has a relatively small amount of computation.
Key words: Fast Fourier Transform, Spectrum correction, Free damped vibration, Gaussian fitting, DSPLIB
