基于ECT图像重建算法的多相流检测研究  

Multiphase Flow Detection Based on ECT Image Reconstruction Algorithm

作　　者：赵玉磊[1] 郭宝龙[1] 

机构地区：[1]西安电子科技大学空间科学与技术学院,西安710071

出　　处：《农业机械学报》2016年第7期368-374,共7页Transactions of the Chinese Society for Agricultural Machinery

基　　金：国家自然科学基金项目(61571346;61305041;61305040);中央高校基本科研业务费专项资金项目(JB141305)

摘　　要：由于电容层析成像（ECT）图像重建的经典算法Landweber迭代法具有半收敛性,从而限制了其在多相流检测中的广泛应用。为了解决这一问题,从数学角度对Landweber法的半收敛性进行分析证明,并找到其物理本质原因。通过构造压缩算子提出一种全收敛的Landweber法,使得该方法具有稳定的收敛特性。同时,对ECT敏感场的＂软场＂特性进行分析,针对忽略＂软场＂特性所导致的经典Landweber法对不同流型的最佳迭代次数不一致的问题,利用最小二乘支持向量机对一定数量的图像样本进行训练,从而得到一个先验条件,并基于该先验条件提出一种自适应的迭代停止判据,实现在图像重建结果最接近多相流实际分布时停止迭代。仿真结果表明,改进后的方法不仅具有稳定收敛性,而且与Landweber法相比,图像重建精度可提高16%～50%。Although Landweber method is a classical algorithm for image reconstruction in electrical capacitance tomography（ ECT） system, the application of Landweber method in multiphase flow detection is limited due to its semi-convergence. To solve this problem,this paper analyzed and proved the semi-convergence of Landweber method mathematically so as to explore its physical properties. Based on this,an improved Landweber method with full and stable convergence was proposed by structuring a compression operator for Landweber. Then the ＂soft field＂characteristic of sensitivity field in ECT sensor and its effect on sensitivity distribution,which is an important basis for image reconstruction,were analyzed. The sensitivity distributions for each typical electrode pair under different flow patterns were given in three-dimensional graphics. As ignoring ＂soft field＂characteristic leads to inconsistency of the best iteration times of Landweber for different flow regimes,an adaptive iteration stopping criterion was proposed. The criterion is based on a priori condition obtained by training a number of image samples with least square support vector machine. With this criterion,iteration can be stopped when the image reconstructed is the closest to the actual distribution of multiphase flow. Meanwhile,the effect of ＂soft field＂characteristic on image reconstruction could be compensated. The experimental results prove that the method not only has a stable convergence,but also can improve the image accuracy by 16% ～ 50%.Therefore,the full-convergence Landweber method can be widely used in none real-time multiphase flow measurement and detection system for its high detection precision.

关 键 词：多相流 检测 图像重建 电容层析成像 Landweber法 

分 类 号：TP274[自动化与计算机技术—检测技术与自动化装置]