METHODS OF OBTAINING INFORMATION ABOUT THE THREE-DIMENSIONAL SCENE TO SOLVE PROBLEMS OF DETERMINING THE SPATIAL POSITION OF OBJECTS WITH A REGULAR STRUCTURE

Abstract

In this paper the basic methods of determining the coordinates of cylindrical objects to control the geometric parameters of an object with a regular structure are considered. Predominantly the considered methods are used in determining the parameters of fuel rods (installations) of fuel assemblies at a nuclear power plant. The purpose of this work is to analyze the existing methods for determining the geometric parameters of objects with regular structure. To achieve this goal, it is necessary to solve the following problem - to compare and conduct a study of existing methods for determining the geometric position of objects with a regular structure and to identify their measurement based on a particular method. Comparative analysis included a description of existing contact and non-contact methods (measurements of linear dimensions of three-dimensional objects, measurements of geometric parameters of an object in space and a device for its implementation and three different methods of controlling linear dimensions of three-dimensional objects by three Cartesian coordinates). The following tool was used for the determination - the object under study was photographed by one video camera on a radiation-resistant CCD from two defined points in space. The image points of the object were identified on the obtained images. Then, using the data on atomic rector dimensions and video camera parameters, we calculated the spatial coordinates of the object points in the object coordinate system and the elements of external orientation of the images. The approximate values of the unknowns needed to solve the problem were determined in advance, using the methods known in photogrammetry. The analysis showed that the most effective are non-contact methods based on processing images of the scene formed by video cameras based on mosaic photodetectors. Thus, measuring systems based on television sensors (video cameras) are the most expedient for measuring the height difference of an ordered sequence of cylindrical objects. The considered mathematical model has allowed to define a methodical error of measurement of geometrical parameters by reconstruction of a threedimensional scene on a series of images in conditions of the non-contact definition, caused by imperfection of the defined measuring method or the simplifications admitted at measurements. On the basis of the obtained data, it is possible to determine the center of gravity of the fuel assembly head, for which the methodological error is minimal, and, accordingly, to take it as a basis, relative to which to calculate the height difference of all steel heads of fuel assembly.