Home – Home – Jornals – Avtometriya 2019 number 6

A control method and software structure for solving the problem of control of motion of a group of robots along a prescribed trajectory with preserving the chosen configuration under the conditions of unsteady dynamic characteristics of individual robots is proposed.

This paper deals with the synthesis of a combined output control system for a nonlinear non-affine plant with delay in the control channel operating under conditions of a priori parametric uncertainty subject to external interference. The simulation results confirm the performance of the synthesized control system, and the resulting controller provides tracking of the plant output after the reference signal.

A metal-dielectric narrow-band filter for a wavelength of 270 nm is calculated within the framework of the conductive surface model for characterization of the properties of thin metal films. It is demonstrated that inclusion of four thin molybdenum films to the dielectric structure ensures effective transmission cut-off at <1.5 % in the visible range of the spectrum with the maximum transmittance more than 50 % for the identified wavelength and the spectral width of the filter <5 nm.

Application of the method of layer-by-layer selective laser sintering of a metal powder for depositing capillary-porous coatings with a prescribed porosity onto heat-releasing surfaces is considered. Implementation of this method in experimental investigations of the boiling process on modified surfaces allows broad-range variations of the main parameters of microstructured capillary-porous coatings and other three-dimensional structures: material, porosity, amplitude (height), thickness of the residual layer and wavelength of capillary-porous coatings, and size and shape of three-dimensional ordered microtextures. It is demonstrated that the use of this technology can increase the coefficient of heat release in the case of boiling on the surface with a capillary-porous coating by several times as compared to the uncoated surface.

In this paper, we consider the two-signal method and a modified two-signal method for measuring the S-parameters of passive two-ports poles and a method for adequately measuring the S-parameters of two-ports, such as transistors, developed on their basis. The methods are implemented by a coaxial simulator/analyzer of microwave amplifiers and oscillators in its measuring channels matched or mismatched with loads. The field of application and the interrelation between these methods are investigated, and their advantages and disadvantages are discussed. Data on the maximum measurement error of the methods are presented.

Based on an analysis of differences between the experimentally measured temperature dependence of the current-voltage characteristic (I-V curve) of a laser diode bar (LDB) with AlGaAs/GaAs heterostructure and the dependence obtained in accordance with the well-known model of light-emitting diodes, assumptions were made about the sources of these differences. The agreement between experimental and modeled dependencies is significantly improved by taking into consideration the change in the resistance of LDB layers caused by temperature change. It is shown that when the injection current is known, the measured voltage drop across the LDB can be used to estimate the temperature of the diode active region in order to implement thermal stabilization for solid-state laser pumping systems based on high-power laser diodes.

A classifier for operation with 1 pixel image fragments is proposed. Separation of elements into an object and background is based on posterior probabilities, which are calculated using a histogram. A computational experiment has shown that the developed algorithm provides a more accurate classification than the separation according to the brightness threshold determined from the condition of the minimum weighted sum of errors of the first and second kind.

Several approaches to the use of neural networks for detecting objects on spatially inhomogeneous backgrounds are considered. A method for constructing a classifier for detecting objects directly from observed fragments has been implemented. An approach consisting of a combination of the matched linear filtering method and convolutional neural networks is proposed. It is shown that this approach reduces the likelihood of false alarms while maintaining the object detection probability.

The existence of internal structural defects in Gas Insulated Combination (GIS) seriously affects the normal operation of equipment, and it needs an efficient and non-destructive detection method. This study is focused on the feasibility of X-ray digital imaging detection in GIS equipment monitoring. First, the digital imaging detection process is briefly introduced. Then, in order to obtain high-quality digital images, a correlation coefficient is introduced to improve the nonlocal mean filtering denoising algorithm. In terms of image enhancement, a histogram equalization method is introduced, and then an improved contrast-limited adaptive histogram equalization (CLAHE) method is proposed for image denoising. The detection system and image processing method of this study are used to detect two GIS equipment units of the Chongqing Electric Power Company. It is found that this method clearly and accurately detects the equipment defects and proved its reliability. This study provides some theoretical basis for the further promotion of the X-ray DR technology in GIS equipment defect detection.

A method of fast bandwidth selection in a nonparametric algorithm of pattern recognition corresponding to the a posteriori probability maximum criterion is proposed. The algorithm is based on the results of studying the asymptotic properties of the nonparametric estimate of the separating surface equation and probability densities in solving a two-alternative problem of pattern recognition. The proposed method is compared with the traditional approach based on minimizing the classification error probability estimate.

Effect of nonlocality on the polarization dynamics of an electric field pulse in a medium with cubic nonlinearity is under study. Nonlinear equations are solved using a variational approach. It is shown that nonlocal and chiral effects cause trajectory oscillations and nonlinear rotation of the soliton pulse polarization of the field.

Modern aviation industry solves the problem of developing multifunction engines capable of flying both at subsonic and supersonic speeds. An important part in engines is a nozzle of variable cross-section, which allows varying the geometry of the engine exhaust unit and, accordingly, its technical characteristics. This study touches upon an computer vision based optical noncontact method for reconstructing a nozzle shape. The reconstruction requires data recorded by two optical three-dimensional recorders directed toward the inner part of the nozzle when the engine is subjected to ground tests. The diagnosis is complicated by the presence of a hot jet being in the way of the sensor vision, the regime-dependent variation of the nozzle glow brightness, and intense mechanical vibrations. The performed bench tests confirm the efficiency of the proposed method. According to their results, in a low-gas regime, the standard deviation of the diagnosed diameters of the exhaust unit and critical sections for each frame does not exceed 0.3 % of the corresponding sizes. The data obtained as a result of this diagnosis can be taken into account when upgrading the exhaust unit of the engine and the traction control system of a gas turbine engine

SOI biosensors without surface modification are used to detect the Ebola virus VP40 protein by revealing its immune complexes with specific monoclonal antibodies (MCAs). It is shown that the reaction of specific interaction between VP40 and MCAs gives a more pronounced sensor response than direct adsorption of VP40 or antibodies to their surface. The formation of antigen - antibody complexes leads to the accumulation of a negative charge on the sensor surface. The protein and protein - antibody complexes are detected in real time (∼200-300 s per test sample).

A diffraction Fresnel method of precision measurement of diameters of circular metallic cylinders in the range from several units to hundreds of millimeters with an arbitrary coefficient of light reflection from the cylinder surface is developed. The method is based on determining the position of the first maximum in the Fresnel pattern of the object formed in the free space. An expression for the diffraction Fresnel pattern of a plane model of a cylinder fragment is derived in the class of special functions (Fresnel integrals). Based on this expression, a formula is found for taking into account the displacement of the position of the first maximum of the field as a function of the light reflection coefficient. By using an appropriate correcting additive, the measurement error component induced by this factor can be reduced by more than an order of magnitude. The results of the present study can be used for the development of optical-electronic systems of precision dimensional inspection of cylindrical articles.

Reconstruction of a wavefront containing turbulent distortions of optical radiation is considered. The Hartmann method based reconstruction is carried out using the wave function approximation by Zernicke polynomials according to estimates of local slopes and analyzed on the basis of filling hartmannograms with focal spots, depending on the telescope circuitry. The volume and quality of information about phase distortions of radiation are estimated using the hartmanograms formed in the plane of the receiver, thereby developing methods for reducing the the telescope induced residual reconstruction error.

A new method for image recovery from a series of digital holograms obtained by step phase shift with random values of phase shifts is under consideration. It is shown that images recovered from a digital hologram in a Fresnel region at a distance coinciding with the distance from the object to the hologram consist of two parts, one of which is a clear image of the object and the other one being formed by incorrect phase shifts consists of a set of defocused images of the object. At the same time, the quality of the recovered image is slightly reduced. This effect eliminates the necessity to use precision systems for setting the phase shift and significantly reduces requirements for stabilization of the optical device.