Design On Data Acquisition System Of Magnetic Flux Leakage Detection In Pipeline Based On SOPC

Oil transport is of great importance in the development of our national economy. As the pipelines age, pipeline defects bring about leakage accident frequently, which results in loss of life and property as well as environmental pollution enormously. Hence, pipeline transportation safety draws great attention in society. It is the magnetic flux leakage detection in pipeline that is most reliable in nondestructive testing aiming at ferromagnetic pipeline. It is also the major guarantee of pipeline transportation safety. As the core of internal inspection robot, data acquisition system undertakes the vital task of data acquisition and storage. High speed signal acquisition and mass data storage, which provide evidence for defect identification, have important practical significance in reducing the economic loss and protection of natural environment and safety of life and property of residents.In consideration of low sampling rate, resolution and integration degree, in addition, small storage capacity and large power consumption, which are all disadvantages of the existing data acquisition system, this thesis puts forward a new design scheme:use of microcontroller with high master frequency can increase the sampling rate and lower the power consumption effectively; the introduction of NIOSII soft-core processor and establishment of system on chip with SOPC builder narrow the volume of the system, which accomplishes higher integration degree and flexibility of parameter modification of hardware and system upgrade, compared with traditional embedded system; the introduction of secure digital memory card, the proper storage device in situation of handling mass data, which is small in size but large in capacity, with the buffer of serial peripheral interface controller core, which avoids the complicated programming task of interface module, resolves the "bottle neck" problem of mass data storage, which blocks the development of magnetic flux leakage detection technology. The direct data transfer from memory to high speed peripheral by direct memory access improves the speed tremendously.The main content of this thesis is divided into four aspects. Firstly, through the comparison between two system hardware structures, the design with front-loading instrumentation amplifier is determined; the rationality of device selection is proved in sampling frequency, resolution, the gain of amplification circuit and memory capacity according to the performance index; the whole workflow of acquisition system is drafted. Secondly, peripheral circuits and interface circuits of all parts of the system hardware are designed; system on programmable chip is constructed; the data acquisition system provides hardware platform of every part with every controller core as well as first in first out component. Thirdly, every function module is elaborated. Fourthly, traditional filtering algorithms are studied, moreover, new algorithms have been come up with.Many functions are integrated into this system, including analog-to-digital conversion, data acquisition, data buffer and storage. Eight sensor signals are achieved by polling method, which offers basis for feature extraction and defect analysis later. The goals of this design are about to be realized on the basis of the need of magnetic flux leakage detection in pipeline in the sea about sampling rate and movement speed, which are that magnetic induction signals are sampled at the speed of5000times per second and actual capacity is about21GB within100km.