【作者】 石迎军；

【导师】 高印寒；

【作者基本信息】 吉林大学 ， 测试计量技术及仪器， 2004， 硕士

【摘要】 在无损检测的几种检测技术中，相对于其它几种检测技术的发展情况，涡流检测技术仍未得到充分的发展。这里面有一个很重要的原因就是要实现涡流的实时成像比较难。目前涡流成像技术主要有阻抗C扫描成像技术、层析成像技术、磁—光涡流成像技术。本文正是基于阻抗C扫描技术，研制并开发了一套涡流探测成像仪，用于探测被掩盖的金属焊件，由于采用了高速信号处理器ADSP21060来进行数字信号处理，大大提高了扫描速度及缩短了信号处理时间，减少了延迟，本系统可以实现实时成像，能够达到可视化和定位的目的。该涡流探测成像系统主要有以下三大部分组成：涡流信号采集系统、DSP信号处理系统及其接口电路、图像处理系统。系统结构原理图如图1所示图1 系统结构原理图其工作过程如下：来自涡流信号采集系统的信号，一路信号送到高速数字信号处理器ADSP21060，另一路直接送到控制器，通过反馈对采集系统进行控制。同时，控制器对送来的信号进行控制处理和反馈给采集系统和DSP进<WP=65>行控制，另外，通过异步传输送到计算机进行成像处理。数字信号处理器主要完成信号的预处理以及对采集系统和控制系统进行控制。在预处理过程中，主要完成对信号进行A/D转换、滤波、快速傅立叶变换，以及建立信号幅值、相位和扫描座标（x, y）的映射关系，建立信号点和扫描点的关系，为成像做准备。在这个系统中，涡流信号采集系统的原理图如图2所示。图2涡流信号采集系统原理图其工作过程如下：来自线阵涡流传感器的多路信号，首先经过前置放大器进行信号放大，然后通过X-R正交分解器进行正交分解，正交分解器对信号进行相敏检波和低通滤波处理后，再经过多路模拟转换开关，多路模拟转换开关在数字信号处理器DSP的控制下对多路信号进行逻辑切换，这里选用的是多路模拟转换开关AD7502，它同时选通两路，因此前置放大器必须能满足同时两路输入。再经过A/D转换后送入数字信号处理器进行预处理，完成信号的实部和虚部的幅值和相角的预处理，以及它们与扫描坐标的对应关系。本论文从探测实体的角度出发，涡流传感器的结构形式与传统的探伤探头有所不同，所以这里进行了探头的改型设计，采用多检测线圈的线阵排列结构。为了能够进行实时的信号处理与实时成像，本文用一片ADSP21060设计了一种实时信号采集与处理电路。它是一种比较理想的、外具灵活方便的数字接口高速数字信号采集与处理应用电路。ADSP21060本身自带串行口，但在与计算机的通信中有其特殊的困难。本文在通信方面增加一个串行通信控制器PC16550D用于串行口的通信。PC16550D是NS公司生产的异步通信芯片，<WP=66>在通信系统的实时性要求较高时，可通过通用异步通信芯片PC16550D来实现系统的高速串行通信，从而增强系统的通信接口控制能力。ADSP21060与PC机串口通信的硬件电路框图如图3所示。图3 ADSP21060与PC机通信的硬件电路传感器输出信号经测量电路和选择开关后输入到DSP中，首先进行A/D转换，然后进行滤波和校正，量化为8位的数字信号。被测对象经过电涡流传感器获得的原始测量数据往往带有高频噪声，在DSP中进行处理时要将所有数据进行全局阈值化处理，所以在边缘检测的数据处理中，我们采用Marr边缘检测算子对图象数据进行处理。在图像处理的时候，采用了Visual C++ 和 MATLAB联合编程的思想，实现方法为：以 VC++作为界面接收系统参数值，在VC++内部驱动 MATLAB的强大的数据处理和图像处理函数，完成核心数据处理和图像处理。将Visual C++的许多优点同MATLAB的数据运算和图像处理等强大功能结合起来，有效地进行涡流图像的处理。涡流成像技术是涡流检测技术发展的重要方向之一，本文所设计的涡流探测成像系统，有效的开发了涡流成像技术，为涡流检测技术的发展做出了一定的贡献。更多还原

【Abstract】 In the normal nondestructive testing technology, eddy current testing is still not fully exploited in contrast with the other methods. There are some reasons to this situation. First and foremost, eddy real-time imaging is very difficult. At present time the main eddy imaging technologies are Impedance C scan imaging technology, Layer-divided imaging technology and Magic-light converting imaging technology. An eddy current detecting and imaging apparatus has been developed in this paper. It will be used to detect the imbedded metal test piece. Imaging technology of this paper is based on Impedance C scan technology, and some improvements have been made, the DSP (digital signal processor) has been used, the scanning speed has been improved greatly and the time of signal processing and delay have been shortened enormously. The aim of real-time imaging and orientation has been obtained.This system of eddy current detecting and imaging is made up of the three Figure 1 The principle frame of the system <WP=68>parts: signal sampling of eddy current, the pretreatment system and interface circuit and imaging processing system based on computer. The principle frame of this system is figure 1.The working process as follows, sampling signal which comes from eddy current signal sampling system, in one hand, is sent to high signal processor ADSP21060, in the other hand, it is sent to the controller, and it will control the sampling system by feedback and send the signal to the DSP after been processed, simultaneously, the controller will transfer the signal to the computer for imaging processing by asynchronous communication. The DSP mainly do the job of pretreatment and the control of the controller, during the pretreatment, it will realize A/D conversion, wave filtering, FFT and construct the mapping relation of amplitude and phase and the coordinate (x, y) of scanning sensors. It prepares for later imaging The signal sampling system is very important .The principle figure of signal sampling system of eddy current is figure 2Figure 2 The principle figure of signal sampling system of eddy currentThe working progress as follows, the signal from line-array sensors is first amplified by the preamplifier groups, the X-R separator separates them into two vertical channels and get the real part and the virtual part of impedance signal so that they can be processed separately, then selected two channels and transferred by the AD7502, then they will be transferred to the DSP for pretreatment. The DSP will pretreat the corresponding relationship between amplitude and phase of the real part and virtual part, and the relationship between them and the coordinate of scanning system. The AD7502 make logic switch under the control of DSP, it can select two channels at the same time, so the preamplifier also has two channels <WP=69>input and output. This paper is based on detecting the reality. So the structure form of the eddy current sensor id very different from the traditional inspection sensor. The sensor has been modificated and designed in a new way. The array structure of multi-processors has been adapted.The ADSP21060 chip has been adapted in order to realize the real time signal processing and imaging. There is a high speed data signal acquisition and processing circuit with ideal and flexible data interface in this paper. Although ADSP21060 has serial port itself, it has especial difficulty in the communication with the computer. In this paper a serial communication controller (PC16550D) is used to connect the serial port. PC16550D is the universal asynchronous communication chip made by National Semiconductor Company. To meet the requirement of the communication in real-time processing, PC16550D is used to implement high speed serial interface communication of system. To content the requirement of the communication system in real time processing, we can implement high speed serial interface communication of the system, meanwhile the control ability of system communication interface can be intensified.更多还原