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.