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.