卷 21, 编号 1 (2020)

A semi-analytical method for calculating elastic-hydrodynamic contact based on the partial use of Computer Aided Design / Computer Aided Engineering (CAD / CAE) packages and solutions of the integral equation of functional relationship between pressure and deformation have been described. The pressure in the lubricating layer is described by solving the modernized Reynolds equation taking into account the factors such as elastic deformation of surfaces in the contact zone, cavitation effect in the low-pressure region, and variable viscosity of the lubricant layer, which depends on thermodynamic parameters. Based on the stationary solution, a tensor damping coefficient has been obtained, with the help of which calculations of transient non-stationary modes that occur in cases of a sharp change in the external load have been further performed. A comparison of the results of modeling a plain bearing obtained by using the proposed semi-analytical method has been made and the full calculation performed using CAD / CAE programs such as ANSYS and COMSOL Multiphysics. The comparison showed good convergence of all numerical methods. At the same time, the “hybrid” method showed a number of advantages over  direct calculations in CAD / CAE packages, such as: faster calculation speed, low requirements for computing resources and accounting for the cavitation effect. The described semi-analytical method allows to create digital twins of bearing units, centrifugal pumps and hydraulic supports used in satellite cooling systems and in rotary mechanisms of ground-based satellite dishes.

The article proposes an approach to developing the architecture of a service-oriented information processing system, modeling and process control. The system, which is being developed, is a tool for identifying, predicting and controlling discrete-continuous processes. Its mathematical apparatus is based on nonparametric algorithms of identification and control. The software architecture includes the following main modules: the module for processing data, modeling and forecasting output process variables and the process control module. The first module includes data preprocessing algorithms: normalization, centering and analysis of outliers and omissions. The modeling module is an algorithm for research and recovery dependencies between process variables, process identification using nonparametric estimation of the regression function from observations. The last module is an implementation of nonparametric dual control algorithms. Control devices built on the basis of these algorithms perform functions of both object control and its study.

The article discusses the application of architectural solutions based on two proven approaches in the field of software development: the composite approach and the service- oriented approach.. The main principles of composite architecture as a set of software systems with many characteristics that perform a specific task and service-oriented architecture as a modular approach to software development are described. The advantages of the applied composite service-oriented architecture over other variants of software architecture for control systems are shown, in particular, monolithic software architecture is compared with composite service-oriented architecture. This means that a researcher can use a single operation, which is a logically isolated, repeated task related to the production process of the enterprise. At the same time, it is necessary to ensure positive results when integrating with existing software products of enterprises which greatly complicates and requires the development of new components, as well as support for the "inherited" parts of the system.

In modern conditions of technology development, signs of systemacity are manifested to one degree or another in all areas, so the use of system analysis is an urgent task. In this case, the main factors in this situation are data processing and prediction of the state of a system. Mathematical modeling is used as a prediction method for a given subject area. A mathematical model is a universal tool for describing complex systems representing the approximate description of the class of phenomena of the external world expressed by mathematical concepts and language. The mathematical model can be represented as a set of systematic components and a random component. In this article, the object of prediction is the irregular random component of a model, which reflects the impact of numerous random factors. The origin, nature and laws of variation of the random variable are known, therefore, to simulate its behavior or predict its future value, one needs high degree of certainty to establish the form of continuous distribution function of the random variable. The empirical distribution function is calculated using the sample of random variable values. This empirical function is close to the values of the desired unknown function of distribution. The resulting empirical function is discrete, therefore it is necessary to apply piecewise linear interpolation to obtain a continuous distribution function. 

The predicted random component of time series has been included in the initial regression model. In order to compare augmented and initial regression models, several values were excluded from the time series and new prediction was built. The value of the average approximation error for assessing the quality of the model is calculated. The augmented regression model proved to be more effective than the original one.

Any space computing complex is a complicated system. A complicated system is understood as a set of functionally related heterogeneous devices designed to perform certain functions and solve problems facing the system. One of the important characteristics of a system is its uptime. This characteristic is often considered to be a random variable. However, such a mathematical model is quite limited, since the uptime depends on many characteristics (parameters) that describe a system. Therefore, the uptime can be assumed to be a continuous random field (that is, a random function of many variables). It is this approach that is used in this work. If there are certain restrictions on the uptime of a computing system, upper estimates are found for the distributions of a random number of system failures. Therefore, the problem of estimating Gaussian field distribution in Hilbert space arises.

Two theorems that allow calculating the probability of a Gaussian vector falling into a sphere of a given radius are proved in the paper.

The paper is devoted to the reliability of a computing system. The random number of a computing system failures v(r) is a characteristic of its reliability.  The v(r) distribution is the distribution of the sum of a computing system random uptime. It is impossible to write down the distribution v (r) explicitly. Therefore, one has to look for an estimate of these distributions from above. Assuming that the uptime of a computing system is the sum of many variables, the authors of the paper obtained the following results: it is shown that the problem of estimating the distributions of a random number of system failures can be considered as the problem of estimating the convergence rate  in the central limit theorem in Banach spaces; if there are certain restrictions on the uptime of a computing system, upper estimates are found for the distributions of a random number of system failures. The estimates obtained can be used for further research in the theory of computing systems reliability. Knowing these upper estimates, it is possible to predict the level of average costs for computer systems restoration, as well as for the development of special mathematical and algorithmic support for analysis systems, for management, decision-making and information processing tasks.

One of the most important aspects of flight safety is awareness of AC air position (AC is the short for aircraft). The leading method of stating AC airspace location is the use of radar systems – primary, secondary, combined primary – secondary surveillance radars-though radar systems have significant drawbacks. However, at present, more advanced technologies are also in use, for example, ADS-B and multilateration. This article is focused on ADS-B broadcasting. Global coverage, low cost, great amount of obtainable information makes Automatic Dependent Surveillance – Broadcast a highly efficient system. Application of the method for AC air positioning is equally effective for helicopters, especially for those operated by special emergency services. As for the infrastructure of air navigation, the research in this sphere is focused on surveillance systems necessary for reliable control of increasing air traffic. The problem of better awareness of AC air position is still acute and has always been the object of extensive research. At present, home-manufactured civil aviation helicopters are practically never equipped with ADS-B transponders, and hardly ever use the available resources of transceiver-based surveillance systems. The objective of the analysis presented is to demonstrate the applicability of Flightradar system options, as well as implementation of ADS – B transponders for helicopter fleet. Operating surveillance systems like Flightradar may considerably increase flight safety by improving the awareness of helicopters current air position.

High complexity and cost of developing flying models necessitate the use of such design and production techniques that would ensure the best flight technical and technological characteristics of the model also would raise of it operation effectiveness. These techniques include the experimental control method of flying model’s mass-inertia asymmetry parameters during final assembly of the model. Solution of the problem of optimization the process of bringing parameters of mass-inertia asymmetry of the conical flying model to specified standards is considered in the article. The only correction plane is designed to be positioned close to cone face, away from the center mass of the flying model. The flying model as a component of prefabricated rotor is being balanced in dynamic mode on a low-frequency dynamic vertical stand, which based on gas bearings. Before balancing experiment the weigh, longitudinal center of mass and inertia moments of the flying model have to be controlled with use of another measurement equipment.  As a criterion of optimization is sorted the reaching of minimum of the angle of deviation of principal longitudinal centroidal axis of inertia from geometrical axis of the flying model. But simultaneously the pre-set standard of center-mass shift from the geometrical axis must be ensured. Balancing algorithm, easy-to-realized by modern computers, is presented. Numerical illustration of balancing is given. The algorithm enables omitting intermediate steps of balancing, reducing them to one step (as a rule), and shortening the balancing time, as well. In one step of balancing the engineering model permits either bringing parameters of mass-inertia asymmetry of the flying model to specified standards, or diagnosing impossibility of attaining the specified standards with available design of flying model. The algorithm and balancing method are experimentally tested at newly-designed vertical dynamic stand on conical gas bearings. It’s high precision and efficiency are corroborated.

Heterogeneous energy sources and homogeneous energy sources with different characteristics are frequently used in autonomous power supply systems. Solar batteries are widely used as primary energy sources for on-board power supply systems of spacecrafts, unmanned and manned aircrafts. Renewable energy sources such as solar, wind, geothermal and hydro energy, serve as primary energy sources of terrestrial autonomous power supply systems.

Matching primary energy sources with different characteristics and operating conditions within a unified power supply system leads to problems connected with the power control of energy sources, which determines the relevance of the considered problems.

The main aim of the study is to develop a combination of primary energy sources and control techniques which allow using primary energy sources with different characteristics and operating conditions in unified autonomous power supply system.

The objectives of the study are to create the simulation model of a power supply system using MATLAB/Simulink software; to develop and test control algorithms for primary energy source controllers that would allow to maintain the needed battery charging current; to develop and test control algorithms for primary energy source controllers that would allow the primary energy sources to operate in the maximum power point tracking mode and to minimize the maximum power point search time.

Methods used in the study: the simulation of a power supply system using MATLAB 7.9 Simulink software.

Results: the simulation model of a power supply system including two primary energy sources with different characteristics is designed. In the case of excess power generating by the primary energy source, its controller operates in the battery charging mode. When the primary source power shortage occurs, its controller operates in the maximum power point tracking mode. The proposed power supply system structure allows controlling two energy sources independently, thus the primary energy source controllers can operate in different modes. This provides flexibility of the power supply system. The use of fuzzy logic control algorithm increases the accuracy and search speed of the maximum power point tracking algorithm. Simulation results confirmed the efficiency of the proposed solar controller operation algorithms in all modes stated above. The efficiency of controller operation modes selection algorithm was confirmed in different operating conditions. The proposed algorithms allow implementing the effective control of primary power sources depending on power supply system operating conditions.

Materials exhibiting connection between electrical and magnetic properties are attractive for possible use as an element base in microelectronics, spintronics, and sensor devices. Compounds with mixed valence exhibit a number of metal-insulator phase transitions, magnetic phase transitions, including changes in magnetic properties without changing magnetic symmetry.

Promising materials for studying these effects are cation-substituted Mn_1−xRe_xS compounds (Re = 4f elements) synthesized on the basis of the antiferromagnetic semiconductor of manganese monosulfide. The latter is of practical importance in the development of new materials for temperature sensors, widely used in the metallurgical industry.

The structural and electrical properties of compounds with mixed valences Tm_XMn_1-ХS (0 ≤ X ≤ 0.15) and Tm_XMn_1-ХS (0 ≤ X ≤ 0.25) were studied in the temperature range 80–1100K. The regions of existence of solid solutions of Tm_XMn_1-XS sulfides with an fcc (face-centered cubic) lattice of the NaCl type were determined. It was found that conductivity decreases upon the substitution of manganese cations with thulium ions and the lattice constant increases more sharply in comparison with Vegard’s law. When ytterbium ions are substituted, the conductivity increases with increasing concentration and the temperature dependence has the form typical of semiconductors.

The analyzes of the requirements to 3D-configuration pipelines production at the rocket and space industry enterprises is done. A review of different approaches to pipe bending technology (with heat treatment and without heat treatment) is carried out. The object of the study is the bending process and a universal bending machine for pipelines’ production of complex configuration. The article is divided into four sections, which consider the key factors, causing directly the effectiveness of the technological operation of pipeline bending of a complex 3D-trajectory. An overview of no-temperature shaping of the pipeline is given in the first section. The requirements to the technology, excluding: corrugation, flattening, stretching and thinning of pipeline walls during their bending, are considered. The actual regulatory documents and industry aerospace standards, regulating production of pneumatic and hydraulic pipelines are given. An example of calculating the minimal allowable bend radius of the pipe, depending on the diameter and thickness of the pipe wall, is given. The requirements to unification of the pipe size production and gaps are listed. The dependence of the maximal allowable internal pressure in the pipeline is shown. The requirements to equipment, used in pipeline bending and to the design of the pipe bending machine are considered. In the second section, the possibilities of temperature influence on the pipe bending process are viewed. The analysis of patent and technical literature and six possible methods of effective thermal effects are presented: heating of the whole pipeline length, narrow zone heating of the bend pipe place, water cooling with nitrogen in the pipe, laser-cooling of atoms of the pipes, application of the petroleum products on the place of heating of the pipe and using of modern fillers inside the pipe to change its temperature. In the third section the tasks of the development of a universal bending machine are set; the system of the algorithm of the universal bending machine operation is considered; the system of algorithm of the bending machine operating with CNC is shown. The General functional scheme of the bending machine and the sequence diagram of the equipment operation is given.