Home – Home – Jornals – Avtometriya 2021 number 3

To improve the operational characteristics of multi-element photodetectors with spatially nonuniform sensitivity, sensitivity equalization based on their calibration is applied which must be repeated from time to time during detector operation due to the temporal drift of its parameters. Specialists are interested in methods of calibration and correction that do not require the use of standard light sources for illumination of the photodetector. The proposed method for evaluating and correcting the nonuniform sensitivity of a scanning photodetector array (PDA) is focused on attenuating the influence of this interference during interframe processing and is based on the analysis of a pair of images formed in the process of mutual displacement of the PDA and the recorded scene. With a known displacement of the images along the columns located in the image overlap zone, an underdetermined system of equations is constructed, which is solved by the least squares method (LSM). A method for correcting the solution error caused by the underdetermination of the system is presented. A numerical experiment has confirmed the effectiveness of the method in application to interframe background suppression and detection of moving small-sized objects.

The method of active jamming suppression based on differences of space-time signals and interferences of spectral characteristics in radiotechnical systems with antenna arrays is proposed. An expression for the spectrum of the space-time signal in antenna arrays is derived. The results of experimental studying of the developed algorithm for different numbers of active jamming sources is presented.

Problems of structural optimization of networks for various purposes are studied in order to obtain the most reliable topologies under conditions of random failures of network elements. Several indicators are considered as reliability, while nodes of the network are subject to failures. To accelerate the search for optimal solutions, an approach is used with a cumulative updating of the network reliability bounds, which makes it possible to cut off insufficiently reliable variants at the early stages. Within the framework of this approach, we propose to evaluate the reliability by the trends for known reliable variants at intermediate stages of optimization. The results of numerical experiments are presented.

The problem of determining the distance from an arbitrary point to the center of an interference band with a known profile from data distorted by random noise is posed. The developed algorithm uses the Wiener-Kolmogorov filtering at the final stage of obtaining the estimate. Numerical simulation shows that the average error of the estimate calculated by the proposed method is smaller by 50-75% than that obtained under the assumption of no noise. The results of the experimental data processing also confirm the effectiveness of the proposed method.

The paper focuses on the methods of dynamic control of nuclear fuel microobjects, both designed and approbated. These methods are based on the reconstruction of spatial geometric properties of microobjects with the usage of the outlines of two-dimensional shadow projections. To describe the microobject dimensions, the overall dimensions and average diameter are taken into consideration. To describe the shape factor, the non-sphericity coefficient is defined as the ratio of the maximum to the minimum overall dimension of an object. The metrological characteristics of the designed control methods are considered.

In this paper, we consider the possibility of using reinforcement learning systems for solving control problems under conditions of a lack of a priori information about the control object. The paper presents a solution to the problem of training the system by the Deep Deterministic Policy Gradient method for objects with a transport delay, as well as a comparison of the efficiency of the proposed solution with the classical method based on PID control, calculated using extended amplitude-phase-frequency characteristics and the Ziegler-Nichols method.

The paper justifies the danger of the contact between the fan impeller blades and the gas turbine engine (GTE) case, determines the factors affecting the radial clearance in flight, identifies the main causes of the contact, analyzes the current means of determining the radial clearance of the GTE, and proposes a technique for detecting the contact between the GTE fan rotor blades and its case in flight based on complex processing of the signals of the fan body vibration and pressure pulsation detectors behind the fan. Implementing an identification technique based on processing of vibration and pressure pulsation signals will improve flight safety, especially for prototype GTEs at the first flight test stages, without the need for additional preparation and installation of complex clearance control systems. This technique can be used to identify the contact when the radial clearance is extremely reduced, which will allow for the timely selection of the mode setback (where possible, at the stage of flight it occurred) to prevent significant damage caused by the contact.

A method of computer simulation of a network device using its digital emulator and creating a digital environment for generating network traffic through it is presented. The emulated objects are represented by a set of functional and interface threads interacting through virtual communication lines, which are shared memory areas. This approach allows one to minimize the time spent on transferring packets between virtual devices of the emulated system and focus attention on the algorithmic component of the simulated device. As an illustration of the method, a computer simulation of the operation of a filtering device for the HTTP protocol as part of an information Web-system is demonstrated.

Time interleaved analog to digital converters (TIADCs) are used when high sampling rates are required. However, TIADCs have offsets such as the sampling time, gain, dc, and phase offsets. Due to these offsets, the reconstructed signal from TIADCs is erroneous. Hence, these offsets should be estimated and then corrected. The proposed work focuses on the estimation and correction of the offsets. For the estimation of offsets, the differential evolution optimization algorithm is used, and the correction is applied using the estimated offsets. The estimation is evaluated by finding the bit error rate (BER) and the signal to noise and distortion ratio (SNDR). The estimation and correction are implemented for 7 and 8-channel TIADCs in an orthogonal frequency division multiplexing (OFDM) system with 4-QPSK modulation. The technique is evaluated by applying monotonic sinusoidal and image signals to the OFDM system.

The value of the limiting specific power of capacitive electrostatic motors with a metal - thin-film ferroelectric structure with a large specific capacity - nanogap - movable electrode is determined. The maximum possible frequency of power conversion for such motors is estimated. Using the previously determined value of the limiting energy density for energy converters based on such structures, it is shown that the limiting power reaches 5· 10⁸ W / kg and exceeds the power of inductive motors by 5 orders of magnitude.

The study is devoted to the development and research of a model of a pulse laser location system without the use of an image intensifier as an external shutter. The system is designed to detect retroreflective objects, including optical and optoelectronic surveillance devices. A description of the hardware and capabilities of the created special software is presented. The results of measuring the dependences of the signal value on the angle of rotation of the retroreflective objects relative to the direction of the optical axis of the pulse laser location system, on the distance to the object, and on the value of the aperture of its lens are presented. The parameters of retroreflection of typical video recording devices in real conditions are determined experimentally. A method is proposed and demonstrated for calculating the maximum detection range of retroreflective objects in the presence of information about their retroreflective index by measuring the informative signal at deliberately shorter ranges with an increased degree of diaphragming.

Specific features of the formation of images of an asymmetric edge of a 3D-object with an absolutely reflective internal surface are analytically investigated from the viewpoint of dimensional inspection. Formulas are derived for calculating fields in images of object faces in ideal and diffraction-limited systems depending on the magnitude of the object bevel с , phase shift ϕ of the wave reflected from the inner surface of the object, and angular aperture 2θ₀ of the coherent projecting optical system. For metallic 3D-objects (ϕ = π) the value of the field in the image of the back face at a point x₁ = c, corresponding to the position of its boundary is found to be negligible if the depth of focus of the system is much smaller than the object thickness. For object bevels с much smaller than the size of the Fresnel zone δd ~ √λd(λ is the light wavelength, and d is the object thickness) and greater than the depth of focus ∆z, the displacement of the intensity profile in the image of the front face is proportional to c/δd and depends on the angle ϕ. With large bevels, when c >> δd and Δz >> d, the displacement of the front face boundary is inversely proportional to c/δd. These displacements can lead to systematic errors of measuring the boundary positions of the 3D-object and should be taken into account in precision dimensional inspection.

The reflection of infrared radiation from diaphragm coatings in photodetector devices: black polymer paint, anodic oxide, etched kovar, suspension of graphite or titanium oxide in cryogen-resistant varnish, and others are investigated. The spectra and integral reflection coefficients of the diaphragm coatings in the wavelength range of 2÷14 microns at the radiation incidence angles of 15 and 45 ^◦ are elucidated. The levels of reflected infrared radiation in the spectral ranges of 3.4-4.8 and 7.5-13.5 microns are also studied in a wide range of angles from 0 to 80° for a radiation incidence angle of about 15°. According to the research results the lowest level of infrared radiation reflection is provided by the coating of a graphite suspension in a cryogen-resistant varnish (developed at the Novosibirsk Branch of the Institute of Semiconductor Physics of the Siberian Branch of the Russian Academy of Sciences “Technological Design Institute of Applied Microelectronics”, Novosibirsk). The integral reflection coefficients for this coating are 3.98% (in the spectral range of 3-5 microns) and 5.69% (in the range of 8-12 microns).