Статьи журнала - Siberian Aerospace Journal
Все статьи: 352
Статья научная
Today, there are many approaches to developing parallel programs. It is considered that it is more efficient to write such programs for a particular computing system. The article proposes to ignore the features of a particular computing system and outline plans for the development of a certain automated system that allows trying to improve code efficiency by developing programs with unlimited parallelism, as well as explore the possibility of developing more efficient programs using the restrictions imposed on maximum parallelism. This approach was demonstrated on the example of the analysis of various matrix multiplication algorithms. As a mathematical apparatus, the study considered various approaches to the description of algorithms to increase their implementation, including an approach based on unlimited parallelism and, also, an approach based on various restrictions on parallelism is proposed. In the course of the work, sequential and parallel methods of matrix multiplication were studied in detail, including tape and block algorithms. As a result of the study, various matrix multiplication methods (sequential, with left and right recursion, parallel methods) were studied and more effective ones were found in terms of the resources used and the restrictions imposed on parallelism. A sequential method and a cascade summation scheme were analyzed and proposed as possible ways of convolving the results of solving the problem obtained after the decomposition stage. Also, a number of programs with different levels of parallelism were developed and implemented in the functional-stream parallel programming language. In the future, such transformations can be carried out formally, relying on a knowledge base and a language that allows equivalent transformations of the original program in accordance with the axioms and algebra of transformations laid down in it, as well as replacing functions that are equivalent in results and have different levels of parallelization. These studies can be used to increase the efficiency of developed programs in terms of resource use in many branches of science, including in the field of software development for the needs of astronomy and rocket science.
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Статья научная
The article provides an overview of current methods for measuring and controlling the tension force of the material of the spacecraft metal-mesh reflectors. The purpose of the research: to obtain the most accu-rate results of measuring the mesh tension. Based on the review, a comparative analysis of the advantages and disadvantages of each of the considered methods was carried out, when measuring the tension force on mesh for large-sized transformable spacecraft reflectors. In the article considered the methods of force measurement: photo method, the operation principle of which consists in the sequential photographing of a mesh on reflector frame certain zones; a method based on pattern recognition, similar to the photo method, but using an information and measurement system with a given information processing algorithm; a meth-od based on local membrane deformation, related to the contact type, in which the mesh tension measure-ment is defined as a reaction from the impact of physical force on the mesh surface; a method based on the influence of sound waves impact, which is based on the influence of sound waves impact on the mesh sur-face. The experimental part of the research described in the article includes the measurement of the mesh tension by the resonance method, as the most optimal method according to the analysis. The prospects of possible use of the resonance method in the aerospace industry of radio-reflecting surfaces of spacecraft antennas are proposed and analyzed. According to the results of the conducted research, the dependence of tension force of mesh is established on the sound vibrations frequency affecting the mesh, at which reso-nance occurs.
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Research of the motion parameters of a spaceplane entry of into the atmosphere
Статья научная
After cessation of operation of the International Space Station in 2028, the Russian Federation plans to develop a national orbital station project. The Russian Space Station will differ from its predecessor in a greater practical aspect. One of the tasks assigned to the station will be the launch and management of a group of small satellites for remote sensing of the Earth, as well as the interaction and maintenance of prospective satellite groups. Due to the limited maneuverability of the orbital station and the potential for a malfunctioning device to be at a significant distance from it, the use of an autonomous spaceplane is proposed to increase the transportation and technical capabilities of the station. The research presents two aerodynamic designs of the spaceplane, and one of them is chosen based on the results of the aerodynamic and weight analysis. The spaceplane configuration and algorithms for its operation on the orbit and descent to the atmosphere are also presented. The goal of the research is to compare the trajectory parameters during the descent of the spacecraft from different descent orbits. For this purpose, a task was specified to determine the dependence of the area of the descent corridor on the initial parameters. The area of the descent corridor is determined by the boundary conditions, which depend on the operational parameters of the spaceplane. A computational program is written to solve differential equations of flight dynamics of a spaceplane by Euler's method in general and by Runge-Kutta method in a computational case. The results of the research are presented as the dependence of the area of the descent corridor on the altitude of descent. Graphical representations of the primary parameters of the spaceplane descent for the computational case are also provided.
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Статья научная
Waffle shells are the main part of the overall dry mass of the products of the aerospace industry. Cell bottom thickness and the width of the longtitudal and circular edges are the main characteristics of the waffle grid. Mechanical cutting by using of the machine tools of SVO series which perform tracking and copying of the opposite wall thus providing the stability of the bottom thickness despite of the workpiece shape errors is the most wide-spread technology of the manufacturing of the waffle grid. There are different other factors which act during such a process and lead to bottom thickness and edge width errors which brings to increase of the weight of the part, use of the additional finishing operations and rise of the defects amount during milling process. Thus it is essential to solve the problem of the increase of the machining accuracy of the cell thickness bottom, which might cause the rise of the machining performance and might help to raise the quality of waffle shells. In order to do this, authors examine in detail the waffle grid mirror milling manufacturing process. The factors which lead to the cell bottom thickness deviations were described and classified. It was analyzed and shown in the paper that deviations of the spindle axis against the surface normal affect the magnitude of cell bottom thickness errors. Authors also perform the mathematical modeling of cell bottom thickness errors because of presence of backlash in tracking system. The paper presents a detailed description of various techniques to increase the machining accuracy of the cell bottom. It was demonstrated that the most suitable is to use the combined digital compensation method by using of self-tuning system. Implementation of the solution will enhance the mass-energy properties of the aerospace products by means of decrease of the overall dry mass by attainment the higher cell bottom machining accuracy. It also will bring to raise of the quality and reliability of production by reducing the defects amount. The mirror milling machining process was considered. The factors leading to the thickness er-rors of the pocket bottoms were classified. Perfomed the simulation of the thickness errors genera-tion caused by the influence of the most significant factors. Techniques to increase the accuracy during machining of the pocket bottoms were analysed, provided the reason of using the combined digital correction method with self-tuning from pass to pass.
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Research on electrical properties of manganese sulphides doped by thulium and ytterbium ions
Статья научная
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 Mn1−xRexS 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 TmXMn1-ХS (0 ≤ X ≤ 0.15) and TmXMn1-ХS (0 ≤ X ≤ 0.25) were studied in the temperature range 80–1100K. The regions of existence of solid solutions of TmXMn1-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.
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Results of monitoring the radiation environment in medium circular orbit
Статья научная
Problem definition – these data will form the basis for the development of technical solutions that will minimize mass, time and financial costs while ensuring the radiation resistance of on-board equipment and the spacecraft as a whole. Goal – the experimental dose control complex measures the level of absorbed ionizing space radiation doses in the sensitive element, assesses the radiation effects influence on the spacecraft, determines spacecraft’s residual radiation resource and refines impact models of the ionizing space radiation, located on an experimental spacecraft “Skif-D”, which was launched into orbit H=8070 km and inclination 90°. Results – flight experiment demonstrated high convergence of the comparative analysis’ results of the experimentally obtained impact levels in orbit of the operation of the “Skif-D” spacecraft with the impact model stated in the Russian Federation Scientific and Technical Documentation (OST134-1044-2007 amend.1 (2017) “Methods of the calculation of radiating conditions on-board of spacecrafts and specification of requirements for resistance of radio-electronic equipment of spacecrafts to the action of the charged particles from the space of natural origin”); Practical value – successful modernization of the ICDRM integral accumulated dose sensors in terms of their miniaturization and transition to a digital output (flight qualification of the sensors was obtained); the prospects of the concept of monitoring the integral accumulated radiation dose using semiconductor detectors with individual mass protection; experimental confirmation of a higher radiation exposure in the range of typical protections for ECB equal to 0.5–3 g/cm², on a 8000 km circular orbit compared to the GEO and 1500 km circular orbit.
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Статья научная
Instruments measuring the Earth's magnetic field are widely used in the space industry. Increasingly, loworbit spacecraft orientation and stabilization systems include magnetometers manufactured using magnetoresistive technology. This is justified by the low weight, size and consumption of such devices, which makes them ideal for use on small-sized spacecraft. However, the main problem of magnetoresistive magnetometers is the need to estimate possible measurement errors. The influence of errors significantly reduces the accuracy characteristics of the device. In order to solve the problem, researchers propose various methods for evaluating and eliminating the influence of errors on measurements [1–7]. Among the ways to eliminate errors in the readings of the device, constructive solutions are used, such as putting the device at a distance from the spacecraft using a retractable boom, in order to reduce the influence of interference on the device from the apparatus [2]. Such a solution is advisable for large spacecraft, where the presence of a retractable boom will not complicate the design and will not increase energy consumption. For small spacecraft, such a solution is not advisable, for this reason, when discussing small-sized spacecraft magnetometers, much attention is paid to calibration methods, mathematical evaluation and error correction, both in ground and in flight conditions. The objectives of the article include the formation of a general understanding of the causes of distortions in the readings of anisotropic magnetoresistive magnetometers, methods of their mathematical evaluation. A review of methods and equipment for ground calibration is carried out. The characteristics of the calibrated parameters of magnetometers are given and a mathematical model of measurement of the device is proposed, taking into account errors. The basic operations and equipment used in the calibration process are described. The results of the work can be useful in designing workplaces for calibrating magnetometers, as well as in conducting empirical research in the field of magnetometric sensors.
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Rigging material selection methodology for aircraft elements design
Статья научная
The development of modern materials and technologies for manufacturing structural elements of aircraft from polymer compositions requires justification for the choice of technological rigging. The physical and technical characteristics of the material, ensuring the required accuracy of rigging manufacturing, as well as economic feasibility are the main criteria for choosing the material of technological rigging. The main criteria for choosing a rigging material are the physical and technical characteristics of the material, ensuring the required accuracy rigging manufacturing, as well as economic feasibility. The choice of rigging material depends on the technology for manufacturing structural elements from polymer composite materials. The paper presents a methodology for selecting rigging material for manufacturing details using the vacuum infusion method. The methodic of rigging materials selection for aircraft constriction elements production from polymer composition by vacuum infusion is considered in the paper. The results of a comparative analysis of typical rigging materials used in production are presented. It is shown that the main criteria for a comparative analysis are: temperature, resistance to solvents, resistance to mechanical stress; maintainability; the value of the coefficient of linear thermal expansion; the stability of the geometry of the rigging and its tightness. The results of the comparative analysis showed that metals and carbon fiber are the most appropriate for the manufacture of rigging, when using high temperatures in the technological process. The paper presents an algorithm for choosing the rigging material for manufacturing the details from polymer composite materials. It is noted that in the manufacture of structural elements based on fiberglass and carbon fiber, the rigging material should be chosen the same as that of the detail. This allows, firstly, to ensure the same CLTE, what is important when hot detail formation, and, secondly, to eliminate the warping of the detail during its cooling on the rigging. However, achieving the specified accuracy of such rigging requires taking into account the processing of the rigging with a gelcoat after its manufacture. The paper presents an approach to quantifying the economic feasibility of the choice of rigging material. It is shown that only a combination of technical, technological and economic factors makes it possible to justify the expediency of the rigging material used for the specific production of aircraft structural elements.
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Saint-Venant and Karman equations for an orthotropic pre-stretched plate under tem-perature
Статья научная
Thin plates that are preliminarily stretched with the help of forces in their plane and attached to rigid ribs are used in space technology. In fire rescue technology, plate designs are being developed that repre-sent a life net supported by drones to cancel the energy of a person falling from a height during his evacua-tion both from a high-rise object and in other exceptional cases. The plates are thin and usually consist of a composite material. Shear forces predominate as loads; to reduce deflection, the life net is pre-stretched onto a rigid contour. In this work the equations of B. Saint-Venant and T. Karman for an orthotropic plate are obtained, tak-ing into account the temperature increment. The former are the equations of equilibrium in displacements with initial forces, and the latter are a system of non-linear equations of deformations continuity and non-linear equations of equilibrium. The form of models’ representation is differential. Examples of plate calculation for the action of a concentrated force and preliminary stretching are con-sidered. The plate continuum is replaced by a discrete region; differential ratios are replaced by finite-difference analogs. Nonlinear equations were solved by iterations. The calculation of a thin plate for the action of a concentrated force showed that the resulting longitudinal forces are so large that the stresses are two to three orders of magnitude higher than the stresses allowed for the considered orthotropic material. To reduce stresses, the plate is pre-stretched. The bending surface be-comes more monotonous, the deflection decreases, which leads to a decrease in the stress level. Comparison of calculations obtained from the action of a concentrated force and temperature changes showed that in this flexible plate of small thickness, the effect of temperature exposure is insignificant. The apparatus of the Karman theory is relatively complex in numerical implementation. The mixed form of the model in stresses and displacements requires additional studies of the convergence of solutions. The Saint-Venant deformation model as a model of a flexible plate with a small deflection makes it possible to solve the problems of ensuring the rigidity and strength of a complex longitudinal-transverse bending of orthotropic plates.
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Savostyanova I. L. 3-dimensional solutions from two variables
Статья научная
In this paper, we consider stationary 3-dimensional equations of ideal plasticity with the Mises flow condition. The material is assumed to be incompressible. The case when all three components of the veloci-ty vector and hydrostatic pressure depend only on two coordinates x, y is studied in detail. For this case, a new name is introduced – 3-dimensional solutions from two variables, to distinguish it from the generally accepted two-dimensional state, when only two components of the velocity vector and hydrostatic pressure differ from zero. It is proved that the system admits, in the sense of S. Lie, a Lie algebra of dimension 10. It is shown that all 3-dimensional solutions from two variables is a superposition of the plane stress state and plastic torsion around the z-axis. Two invariant solutions of the equations describing the 3-dimensional deformed state are constructed. The first solution can be used to describe plastic flows between two rigid plates that approach at different speeds. The second solution is used to describe the stress-strain state of the material inside a flat channel formed by converging plates.
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Search for broadband signals ground-based radio navigation system
Статья научная
In the present paper, a method of temporary search for broadband of frequency manipulation with minimal shift keying (MSK) signals of ground-based radio navigation systems (RNS) is considered. The method is based on a multi-alternative optimal signal detection (the signal may belong to one of the orthogonal signals) using the evaluation-correlation principle of processing (ECPP) under conditions of a priori uncertainty. The problem of representing broadband MSK signal as a signal with double discrete frequency-phase modulation (FPM) was solved. The law of phase manipulation in the form of a binary sequence of elements lb of a length code τ э L (in the “Sprut” RNS, 16383 L , 2.5 э mcs is the duration of the signal element) is defined through the law of frequency manipulation in the form of a binary sequence of elements ld of a known length L code. The representation of the signal in the form FPM allows, during correlation processing, to replace the correlation integral on the interval [0, τ]э L by L the sum of correlation integrals on the intervals [0, τ]э or by L the sum of element-by-element correlations. The calculation of element-by-element correlations allows the use of a matrix apparatus for the ECPP of the analyzed signal. With the technical implementation of the “search” procedure, there is no need to form 2L pairs of reference quadrature signals with the length L of the modulating code, and instead of that a pair of element-by-element correlations is memorized and over time τэ , according to a code element lkd , cyclically shifted by 1 k elements, frequency manipulation and a code element klb , cyclically shifted by 1 k elements, phase manipulation, block-by-block accumulation L of quadrature correlations is performed. The use of upper-left and lower-right triangular matrices with binary elements klb makes it possible to search for broadband MSK signal with additional phase manipulation of a discrete information message. The structure of the optimal algorithm of parallel search for ECPP of the broadband MSK signal with the use of a matrix apparatus, which allows to implement the optimal algorithm “of search” during the duration τэ L of the signal in real time.
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Статья научная
The aim of the work is the calculation and experimental substantiation of the expediency of using (both on Earth and on the surface of other planets) active-reactive type penetrator projectiles (SPART) for solving a number of scientific problems related to the formation of wells in the ground and the delivery of payloads to a certain depth. Research methods: various launch schemes (options for organizing the functioning process) of SPART are considered. The depth of penetration of an active-reactive type penetrator projectile into loam is calculated for the case when SPART is fired from a ballistic launcher located in such a way that the projectile exit velocity is equal to the velocity of its entry into the ground, and the thrust of the propulsion system is twice as great as the static resistance of the soil. From a variety of options, three SPART design schemes are selected depending on the combustion rate of the fuel used to ensure normal operation of the engine. As a result of the conducted calculation and experimental studies to determine the depth of penetration into loam of 152.4 mm penetrator projectiles 4.6 m long, launched from an artillery mount using the same powder charge weighing 18 kg, it was found that from the moment the engine is turned off until it comes to a complete stop, , which is more than twice the penetration depth of the same penetrator projectile if it moved in the soil only by inertia. Conclusion: the results presented in the article can be useful for researchers, graduate students and engineers involved in the creation and operation of aviation and rocket and space technology, and can also be useful for students of technical universities studying in the relevant specialties.
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Self-Configuring Genetic Programming Algorithms with Success History-Based Adaptation
Статья научная
In this work, a novel method for self-tuning genetic programming (GP) algorithms is pre-sented, based on the ideas of the Success History based Parameter Adaptation (SHA) method, originally developed for the Differential Evolution (DE) algorithm. The main idea of the method is to perform a dy-namic analysis of the history of successful solutions to adapt the algorithm's parameters during the search process. To implement this concept, the operation scheme of classical GP was modified to mimic the DE scheme, allowing the integration of the success history mechanism into GP. The resulting algorithm, de-noted as SHAGP (Success-History based Adaptive Genetic Programming), demonstrates new capabilities for parameter adaptation, such as the adjustment of crossover and mutation probabilities. The work also includes a detailed review of existing self-tuning methods for GP algorithms, which allowed for the identi-fication of their key advantages and limitations and the application of this knowledge in the development of SHAGP. Additionally, new crossover operators are proposed that enable dynamic adjustment of the crossover probability, account for the selective pressure at the current stage, and implement a multi-parent approach. This modification allows for more flexible control over the process of genotype recombination, thereby enhancing the algorithm's adaptability to the problem at hand. To adjust the probabilities of applying various operators (selection, crossover, mutation), self-configuring evolutionary algorithm methods are employed, in particular, the Self-Configuring Evolutionary Algorithm and the Population-Level Dynamic Probabilities Evolutionary Algorithm. Within the framework of this work, two variants of the algorithm were implemented – SelfCSHAGP and PDPSHAGP. The efficiency of the proposed algorithms was tested on problem sets from the Feynman Symbolic Regression Database. Each algorithm was run multiple times on each problem to obtain a reliable statistical sample, and the results were compared using the Mann–Whitney statistical test. The experimental data showed that the proposed algorithms achieve a higher reliability metric compared to existing GP self-tuning methods, with the PDPSHAGP method demonstrating the best efficiency in more than 90 % of the cases. Such a universal self-tuning mechanism can find applications in a wide range of fields, such as automated machine learning, big data processing, engineering design, and medicine, as well as in space applications – for example, in the design of navigation systems for spacecraft and the development of control systems for aerial vehicles. In these areas, the high reliability of algorithms and their ability to find optimal solutions in complex multidimensional spaces are critically important.
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Semi-analytical method for calculating elastic-hydrodynamic contact
Статья научная
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.
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Simulation computer model for virtual research of optoelectronic measuring systems
Статья научная
The paper considers a simulation computer model of an optoelectronic system for measuring the point objects coordinates. The model allows optimal coordination of the system links parameters in order to minimize the measurement error. The method of multiple statistical tests which allows accumulating the results of single computational experiments for each specific measurement event with a unique random distribution of links parameters and characteristics, and then carrying out statistical processing of the accumulated results is the main method of computer simulation. As a result of multiple analyses, multi-parameter functional dependencies that provide optimal coordination of parameters controlled by the designer or operator according to the criterion of the resulting measurement error minimizing are realized. The article presents the results of evaluating modeling parameters that reduce the measurement error. It is relevant to apply this method when using the same measuring system in different operating conditions, for different measured objects and when performing various functional tasks since it allows adapting the system for a specific application. The model presented in the article can be concretized for the purpose of evaluating and multi-parameter optimization of particular object parameters, as well as for developing a virtual measuring stand on the basis of the model and its modifications.
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Статья научная
The implementation of efficient communication systems with high data transfer rates requires the usage of signals with a high modulation order. Current trends in the development of communication systems are aimed at orthogonal frequency multiplexing of signals (OFDM – Orthogonal Frequency Division Multiplexing) usage, which allows you to flexibly change the data transfer rate, to reduce the frequency resource by improving spectral efficiency, as well as to combat frequency-selective fading and selective interference. However, the price of such a solution is also high. The high peak-to-average power ratio (PAPR) OFDM signals imposes a requirement for the linearity of the analogical path, significantly reducing the efficiency of the transmitter and receiver output amplifiers, increasing the dimensions and power consumption of the communication system as a whole. The practical novelty of the work lies in the possibility of using the developed method for reducing the PAPR factor in systems with complex communication channels, such as troposcatter and near-field magnetic induction communication systems, where significant effect of selective interference, intersymbol interference, and frequency-selective fading is present. The results of this work give the opportunity to navigate a large number of algorithms for reducing the peak factor of OFDM signals and apply the desired algorithm in a specific task.
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Статья научная
Obtaining electricity from renewable energy sources is primarily due to the exhaustion of traditional natural energy sources, such as coal, oil, gas. Today it is a promising area of development. The adverse impact on the environment of the use of traditional energy technologies is well known and scientifically proven. The use of traditional technologies inevitably leads to climate change, so the topic of the transition from traditional to alternative energy sources is undoubtedly relevant. Using of solar power plants with photovoltaic modules recently has gained relevance. However, the efficiency of such installations depends largely on their correct orientation to the Sun: the more precisely the system is installed, the more energy it will be able to convert. This article presents the results of the development of a simulation model of the solar panel orientation control system. To maximize the production of solar energy, the control system with tracking the Sun is built using fuzzy logic: fuzzy rules are formulated to control the positions of the object relative to the vertical and horizontal planes. The use of fuzzy logic is based on the product model of knowledge, which implies the use of linguistic variables to avoid the limitations inherent in classical product rules. The use of fuzzy control allows to correct the movement of the panel in the shortest time in the autonomous mode, thus reducing the arising power losses. Russian SimInTech dynamic simulation environment for technical systems is used as the system development environment. Simulation model is represented by several subprojects, united in a single database. The system model is implemented using standard blocks and a set of submodels, as well as a programming unit. The result of the work can be tracked in the 3D module of the built-in visual editor, which allows you to display the interaction of three-dimensional models objectively. In order to simplify and more finely implement the work of the project, a system of loading data, sunrise and sunset points, from an external Excel file was used.
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Simulation of the induction soldering process of waveguide paths from aluminum alloys
Статья научная
A system of waveguide paths is a complex structure of various elements with various geometries. Induction soldering based on the induction heating method is one of the promising methods for waveguides fabricating. Induction soldering of waveguide paths has a number of technological features: the melting temperature of the base material AD31 (695–663 0C) slightly differs from the melting temperature of St. AK12 solder (577–580 0C) at an average induction heating rate of 20–25 0C / sec; a wide variety of standard sizes of waveguide paths elements complicates the development and subsequent reproduction of technological parameters of the induction soldering process; zones of maximum heating of waveguide paths elements do not coincide with zones of soldering. Therefore, to solve the problems of controlling the waveguides soldering process, it is necessary to simulate this process. The paper deals with the problem of simulating the process of heating a waveguide during induction soldering. Requirements for the process model have been formed. The model is built on the basis of the differential heat conduction equation. The formed model requirements take into account the geometric parameters of waveguides, the physical parameters of materials, the initial and boundary conditions, as well as the uneven distribution of eddy current density in the waveguide. It is proposed to use the finite difference method for the numerical solution of the heat conduction equation. The process of calculating the temperature at the grid nodes is shown. The authors propose a two-stage solution. At the first stage, at an intermediate time step, the temperature at the grid nodes along the X axis is calculated. At the second stage, the temperature at the grid nodes along the Y axis is calculated. The numerical solution of the difference equations along the X and Y axes is carried out by the sweep method. An algorithm for the numerical solution of the heat conduction equation has been developed.
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Simulation of the mode of electron-beam welding of a thin-wall structure from AD31 alloy
Статья научная
The article contains the results obtained by the authors in the study of the possibility of using electron beam welding (EBW) for thin-walled structures made of AD31 aluminum alloy. Today, EBW of similar de-signs are not used due to the lack of technology. Currently, other technologies for connecting similar struc-tures are used in production, but they have a high cost, the reason for which is due to the high percentage of defects. The method of using EBW proposed by the authors will significantly improve the quality of the joint in thin-walled structures and the reproducibility of the technological mode of welding products. The authors have developed a technological solution to the presented problem, based on many years of experi-ence in the use of models of thermal processes, accompanied by electron beam welding. As a subject of research, modeling of the parameters of electron-beam welding of thin-walled pipes for waveguide paths made of aluminum alloy AD31 is proposed. The article presents the results of mathematical modeling of technological parameters during heating of an aluminum alloy by energy sources equivalent to an electron beam during EBW. The analysis and evaluation of the simulation results was carried out using the optimal-ity criterion developed by the authors. The calculations performed by the authors are based on functional using mathematical models of metal heating by a complex heat source consisting of moving instantaneous point and linear energy sources. The article presents the results of calculations for a plate with a thickness of 0.12 cm, which corresponds to prototypes used in the manufacture of waveguide paths. As a result, by changing such values as: beam current and welding speed, the temperature distribution on the surface of the product during the EBW process was obtained, which showed the applicability of modeling for develop-ing a new technological process.
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Small satellites for sea surface sounding
Статья научная
The paper presents a method of processing signals of radar sensing of the underlying surface using il-lumination from existing spacecraft (navigation, communication) and a constellation of small receiving spacecraft using synthetic aperture antennas. Methods and Results. Small spacecraft have many advantages over large satellites. Thus, they are rela-tively inexpensive to build, take minimal time from design to launch, can be easily modified to solve a particu-lar problem, and create less radio interference. The approach under consideration consists in redistribution of tasks to be solved between the constellation of satellites in orbit. Both regular high-orbit communication satellites and low-orbit satellite communication systems, as well as navigation satellites are represented as transmitter carriers (underlying surface illumination). These space systems use the necessary broadband sig-nal. Receivers of reflected signals are placed onboard small spacecrafts, and one of the tasks of the system is to perform research experiments, including on-line monitoring of fast-moving atmospheric cyclones. The work applies the method of sea surface radar imaging based on reflected signal models. The main results of the research are as follows: (1) possibility to use as a probing signal both a pulse and a broadband signal with a priori unknown modulation law, (2) acceptable resolution, (3) possibility to significantly reduce the system cost as compared to the existing space radars of sea surface survey. Conclusions. As a result of using a multi-position radar system, which uses small receiving antennas with synthetic aperture and sea surface illumination from operating spacecraft, it is possible to move to a qualitatively new level of solving problems of sea surface remote sensing with spatial resolution up to 1 meter, regardless of illumination and cloud cover presence.
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