THE APPLICATION OF COMPLEX DESCRIPTORS IN SOLVING A SLAM TASK

Abstract

The actual problem of determining all six coordinates (three linear and three angular) of the
current position of a mobile robot (unmanned aerial vehicle) from video rangefinder images of the
external environment (volumetric colored point clouds) formed by an onboard integrated vision
system built on the basis of a 3D rangefinder sensor (lidar) and a color video camera while moving
(flying) in an unknown environment is considered. An algorithm of video navigation based on
the use of complexed (video-rangefinder) descriptors is proposed, for the description of which
visual and geometric parameters are used. The rules for the formation of a complex descriptor are
formulated, which ensure the allocation of special (central) points of the descriptor using the
Sobel operator and the calculation of brightness and geometric parameters in its local area. The
addition of the brightness parameters of the descriptor provided by the video camera with the geometric
parameters provided by the rangefinder sensor removes the problem of invariance of the
descriptor to the scale and thereby significantly reduces the complexity of calculations when selecting
it. The rules for finding complexed descriptors corresponding to each other in a sequence
of complexed images are described, based on calculating the difference in brightness and geometric
parameters of the compared descriptors. The estimation of the error in solving the navigation
problem using the integrated descriptors was performed depending on the error of the sensors of
the vision system and the geometric dimensions of the descriptor. By constructing histograms of
the solution of the navigation problem for each coordinate of the control object for all pairs of
descriptors corresponding to each other, a statistically stable high reliability of the solution of the
complete navigation problem has been achieved. At the same time, the error in solving the navigation
task turned out to be an order of magnitude smaller than the error in the formation of complex
images by the technical vision system. The use of complex descriptors made it possible, with a
relatively small amount of calculations, to solve the complete navigation problem with acceptable
accuracy, which provides a solution to the SLAM problem on the onboard computations at the
pace of movement of the control object. The effectiveness of the proposed algorithmic and developed
software and hardware is confirmed by field experiments conducted in real conditions of
various environments.