2017. № 94
The article studies the Dirichlet boundary value problem for the equation of motion of an oscillator with viscoelastic damping in the case when the damping order is greater than one but less than two. Such problems simulate many physical processes, in particular, string vibrations in a viscous medium, changes in the deformation-strength characteristics of polymer concrete during loading, etc. Earlier, in the case, when the order of the fractional derivative is less than one, the authors established basic oscillation properties, using the methods of perturbation theory. They are as follows. All the frequencies are simple (i. e., the amplitude function of the natural oscillation of a given frequency is uniquely determined up to a constant factor); the natural oscillation with the lowest frequency (the fundamental tone) does not have any nodes; the natural oscillations with frequency (the jth overtone) has exactly j nodes; the nodes of two successive overtones alternate. It was also shown, that the operator, generated by the differential expression of a second order with fractional derivatives in lower terms and boundary conditions of Sturm-Liouville type, is a Keldysh’s operator. This makes it possible to establish the completeness of the systems of eigenfunctions and associated functions of boundary value problems induced by second-order differential expressions with fractional derivatives in the lower terms and Dirichlet boundary conditions.
In the case when the order of the fractional derivative is greater than one, the previously used technique based on perturbation theory for the study of oscillatory properties does not work. In this paper, we investigate the Green’s function of the corresponding problem, which allows us to establish the positivity of this Green’s function. From this fact, some oscillatory properties follow for the equation of motion of an oscillator with viscoelastic damping in the case when the order of the fractional derivative is greater than one. Since the application of the first eigenvalues is usually of the greatest interest in applied problems, the results obtained can be applied to evaluate the study of the natural oscillation with the lowest frequency, and also to establish that the fundamental tone has no nodes.
Keywords: asphalt concrete, oscillating properties, fractional derivative, polymer concrete, Green function, fundamental tone
Fluid, gas and plasma mechanics
Effect of averaging method of solid propellant power plant operating parameters on acoustic vibrations damping factor
The article deals with studying the work process stability in a solid propellant power plant (SPPP) chambers with respect to small pressure perturbations. The research method is based on the energy approach, which allows evaluate the gas flow stability, comparing the disturbances energy inflow and outflow. The aim of this study is the analysis of the two time averaging methods of the SPPP chamber parameters – simplified time averaging widely used in the foreign studies of the SPPP stability (No 1), and common time averaging (No 2). The analysis is based on calculations of the first longitudinal acoustic mode oscillations damping factor for the three types SPPP chambers for various applications with tubular grain.
The acoustic disturbances in steady incompressible gas flow propagating in a cylindrical channel with permeable walls are considered. The first oscillation longitudinal mode damping factor is determined with averaging small isentropic perturbation energy equation over the chamber volume and time.
The damping factor as a function of the tubular grain radius of the three SPPP types calculated by two time averaging methods was obtained through computational experiment.
It was found that for all SPPPs under consideration the work process in combustion chamber is more stable while using averaging No 1 to averaging No 2. The greatest difference was observed for the small-scale SPPP. Relative divergences for small-scale, mid-size and large SSSPs are 61%, 32% and 26% correspondingly.
According to the performed studies, a conclusion was made that the time averaging No 2 is more suitable for practical calculations.
Keywords: acoustic instability, energy method, damping factor, time averaging
The problem of setting the boundary conditions on a solid surface for the viscous heat-conducting gas equations becomes very relevant in the case of hypersonic and moderately rarefied flows. The statement of the boundary conditions at the level of gas-dynamic variables results in significant errors for relatively large Mach values (M) and Knudsen (Kn) numbers. Physically adequate formulation of the boundary conditions on active (absorbing or releasing the gas) surfaces is impossible without considering molecular processes.
The kinetic models describing the gas flow at the molecular level make it possible to set the physically adequate conditions on the surfaces with different properties for any flow regime. However, the kinetic calculation of the flow field of complex geometry by is rather inefficient.
The purpose of this work is the development of a physical-mathematical flow model (KIN_NSF) containing the Navier-Stokes-Fourier model (NSF), «joined» to the kinetic model equation of polyatomic gases. The kinetic model is used in the near-wall Knudsen layer. The remaining flow range is described by the NSF model. In the range of the model, joining the approximating velocity distribution function of molecules is recovered by the parameters determined by the NSF model. It represents the expansion of the local-balanced distribution function in terms of the thermal velocity. The expansion coefficients (unbalanced stresses and heat fluxes) are presented in the Navier-Stokes approximation.
The developed KIN_NSF model is efficient enough for the practical applications and at the same time allows setting the boundary conditions at the kinetic level of the gas with the surface interaction processes description.
A series of test calculations has been performed on the example of a flat Couette flow in the intervals . The kinetic model equation for polyatomic gases, NSF and KIN_NSF models were tested.
The results of the calculations revealed that the KIN_NSF model is not much inferior in accuracy to the kinetic model, and it substantially exceeds it in the efficiency. With the KIN_NSF model required a few dozen times less CPU time than the kinetic model.
When describing flows of the dense gases, the economy of the KIN-NSF model does not depend on the Kn number and depends weakly on the M number, which is typical for the NSF model.
Keywords: boundary conditions, Navier-Stokes-Fourier model, kinetic equation, joining the models, Couette flow
Spontaneous emission probabilities for ion ХеII and distribution of excited states in low-temperature plasma of Hall-effect Thruster
Nonequilibrium low-temperature xenon plasma of Hall-effect Thruster (HT) was investigated by spectroscopic measurements in the 250 - 1100 nm range. e Facility and investigation methodology description is discussed in detail in . The problem researched is to find coefficients for all xenon lines using various models and experimental values of the lines intensities, to determine concentrations of excited states (population), to construct distribution of excited states (DES).
Within the framework of the six models the probability calculations including radiative transitions related to the lowest levels are considered. The examined probabilities are tabulated. A comparison is made with the experimentally obtained results of papers [20-21]. Based on the spectrum data, a DES was constructed for each position of the recording equipment: 1) the lens was mounted coaxially with the HET stream and "look" at the center of the channel; 2) the radiation was sel ected by an external lens system perpendicular to the axis of the engine at a distance of 1 cm from the cut; 3) the radiation was taken at an angle of 14 ° to the axis of the HET, starting from the channel cut; 4) - in a different plane, from the position 1 to 12 down.
The distributions for different parts of the plasma jet 1-4 are of the same nature.
For position 2, the distributions were analyzed using the Einstein coefficients calculated with different models. The structure of the DES is sensitive to the choice of the model for calculating the probabilities of radiative transitions. The intermediate type of coupling for the angular dependences of the matrix elements did not lead to the expected result. The DES based on these data had pronounced energy oscillations, what could have been caused by the erroneous determination of the percentage of different states.
The use of the LS- coupling in combination with all three models of calculating radial integrals does not give a wide spread of populations. The DES using experimentally determined Einstein coefficients [20-21]agrees well with the results when the probabilities were calculated in the Hartree-Fock-Slater approximation with the LS- type of coupling.
The concept of a state vector is introduced, as a combination of the distributions of the excited states of an atom with analogous ion distributions. Just as in atomic physics, for each atom, there is a different level scheme (Grotrian) corresponding to the wavelengths of the ruled spectrum, so any plasma has its own "bar code" in the form of individual distributions of excited states of atoms and ions obtained fr om spectra.
Keywords: Xe plasma, Hall-effect thruster, the probability of photo-transitions of XeII, the distribution of excited states of XeII, optical diagnostics
Aeronautical and Space-Rocket Engineering
Design, construction and manufacturing of flying vehicles
Analysis of complexes with unmanned aerial vehicles used by special operations forces of the United States of America
As effective military instruments, used to amplify its political and military influence abroad, mainly in third world countries, the USА is considering special operations forces.
One of the actively used in recent years, the types of weapons the special operations forces of the USА are the complexes with unmanned aerial vehicles, which, in order to enhance the effectiveness of special operations forces, capable of solving the following main tasks:
– obtaining in advance, or constantly in the course of warfare intelligence information about the enemy by its transfer on control points in real time;
the results of targeting on mobile, time-critical and again you manifest to order to command posts, aircraft, ships, and weapons outfitted with equipment retarget in-flight (cruise missiles, sea- and air-based);
– jamming weapons and retransmission signals;
– defeat of enemy on call of duty provisions in the air or on the ground.
Armed forces special operations United States at present-presence of the complexes with unmanned aerial vehicles of various ranges from multi-purpose unmanned aerial vehicles long range reconnaissance unmanned aerial vehicles of small and middle range.
Currently, units of the special operations forces of the USA successfully used the complexes with unmanned aerial vehicles RQ-11 “Raven” and the RQ-14 “Dragon eye”, “Puma” and “WASP AE”, PD-100 “Black Hornet”.
On the basis of the conducted analysis of tactical complexes of the special operations forces of the USА and considered international experience, it is possible to argue that the Armed forces of the Russian Federation:
– is the actual application of tactical complexes with unmanned aerial vehicles in the interests of tactical units and special operations forces;
– is it appropriate to conduct scientific research in the development of miniature unmanned aerial vehicles as a component of the advanced equipment of the Armed forces of the Russian Federation;
– is it appropriate to conduct scientific research in the field of combating tactical complexes with unmanned aerial vehicles a potential enemy.
Keywords: complex, unmanned aircraft, special operations forces, weapons, basic requirements, performance characteristics
The article discusses passive jamming systems development allowing decrease helicopter signature from prospective observation and guidance facilities in infrared, laser and visible centimeter wavelength ranges. The standard ejection unit, as a part of modern helicopters configuration and meant for false thermal targets jettison, was taken as a basis of the suggested system. The false thermal targets ensure signature reduction only within the infrared wavelength range. Thus, the authors suggest supplementing the standard ejection unit with special ammunition to form the cloud (screen) of volume-distributed composition from nano-structured carbon material (technical carbon of “Veil” brand). While furnishing the standard unit, the volume of the chamber, containing the powder, in the suggested ammunition will be 58.9 cm3. With bulk density of 195 kg/m3 of technical carbon of “Veil” brand the weight of powder contained in the chamber is 11.5 g. The number of the ejected ammunition ensuring the cloud (screen) formation depends on the helicopter type, as well as the types of observation and guidance facilities, weather conditions etc. The efficiency of the suggested engineering solutions was confirmed by the results of laboratory and actual test. These results revealed that a) the transmission factor of the technical carbon of “Veil” brand varies within the range of 7% to 15% within the above pointed wavelengths range; b) the absorption of about 85% is reached with technical carbon concentration of 25·10-4 g/ml; c) with technical carbon concentration increase the absorption factor increases either.
The system suggested in the article is able to ensure effective protection of helicopters from prospective observation and guidance facilities due to its wide spectral range and unique electrodynamic properties the technical carbon of “Veil” brand. Further studies will include model developing and experimental studies related to the particles’ distribution of the technical carbon of “Veil” brand particles in the cloud (screen) depending on ejection conditions.
Keywords: ammunition, helicopter protection, volume-distributed formation, passive jamming, signature reduction, technical carbon, radar cross section
Thermal engines, electric propulsion and power plants for flying vehicles
The wide spread plasma conductivity models as applied to certain types electric rocket thrusters give results inconsistent with the experiment data on local and integral parameters of plasma in magnetic field. The goal of this article was development of a mathematical model of electrons flow through the magnetic field, which may be used for parameters computation of such kind of thrusters. Analysis of gas discharges in ion thrusters, such as stationary plasma thrusters (SPT) and thrusters with anode layer (TAL), revealed two specific features of magnetic fields used in them. Firstly, the width of the area with magnetic field is comparable to Larmor radius of electron. Secondly, due to plasma sparsity the electron collision with heavy particles are quite seldom, i. e. . Thus, one of the assumptions included into basis of the “classical” plasma conductivity model is not complying. Moreover, the electron drift in the thrusters under consideration is closed. It allows simplify the mathematical model. Analytical study revealed that an extra electrons velocity component is formed in plasma in the specified conditions. This component, in its turn, due to the Lorentz force results in forming the force, impeding the electron flow through the magnetic field. The magnitude of this force appears proportional to the square of vector magnetic potential gradient. Thus, the author managed to obtain analytical equation for energy consumption associated with electron flow through the weak magnetic field. To evaluate the obtained model error and define the area of its implementation the more complex problem with account for electrons dissipation on heavy particles was considered. Analytical solution for a special case was obtained. It allowed define limitations on application of the suggested model more precisely.
The developed model’s application to SPT and TAL discharge voltage computation revealed close agreement with the experimental data.
Keywords: plasma, magnetic field, electric rocket thruster, stationary plasma thruster, thruster with anode layer
Fundamental research of the properties of high-frequency discharge is needed to improve the energy characteristics of high-frequency ion thrusters. And the development for this purpose a simplified physical model of the dynamics of electrons will allow us to quickly numerically estimate the most favorable conditions that ensure the efficient transfer of high-frequency field energy to electrons in the plasma.
Analysis of the characteristics of an inductive discharge in the gas-discharge chamber of a high-frequency ion thruster has allowed to determine the main dependences for finding the distribution of concentration and temperature of electrons along the radius of the ionizer.
The distribution of the concentration of electrons along the radius of the ionization chamber is determined by the distribution of the potential of plasma arising because more movable electrons leave the plasma volume faster than ions. Using the Harrison and Thompson solution for the flat approximation can be obtained the distribution of the potential of plasma. And, substituting this solution into the Boltzmann equation which connect the potential of plasma and the concentration of electrons, possible to calculate the distribution of concentration of electrons along the radius of the gas-discharge chamber.
The distribution of temperature of electrons, depends on the intensity of the vortex electric field in the volume of the discharge chamber. The induced electric fields are determined by the system of Maxwell’s equations. These fields can be calculated by the finite element method in the COMSOL Multiphysics program.
The comparison of the obtained numerical results with the experimental data is showed the possibility of using the proposed dependencies for a preliminary assessment of the local plasma parameters in a gas chamber of a high-frequency ion thruster.
Keywords: high-frequency ion thruster, inductive discharge, distribution of electrons
On the basis of multifactorial analysis, computational research and tests carried out constructively-similar samples developed the following thermal protection system structures of a combined rocket-ramjet engine solid fuel (KRPD-T):
Also in work the analysis of use on the outer surface of the housing KRPD-T outer thermal barrier coatings — based low molecular weight silicone rubber to protect against aerodynamic heating. Study outer thermal barrier coatings outdoor temperature is confirmed by testing structurally similar samples.
The system of thermal protection allow you to:
Keywords: thermal protection system, rocket ram-jet engine of solid fuel, external and internal elastic thermal protective coatings, carbon-carbon composite materials with surface and volume silicization, carbon-ceramic composite materials
Dynamics, ballistics, movement control of flying vehicles
The article considers the spacecraft interplanetary transfer from circular low Earth orbit to circular low orbit near Mars by propulsion system with constant values of thrust and specific impulse. The main goal of the article consists in null length gravispheres method inaccuracy estimation.
Due to the nearness of planets’ phases, the simulation revealed substantial for heliocentric phase value of excessive hyperbolical velocity on the edge of gravispheres. while applying conventional technique, imposing the null value of excessive hyperbolical velocity for the trajectory conjugate phases and the planets’ heliocentric phase. These simplifications affect the transfer effectiveness figures, namely, transfer duration and final mass. Another factor, defining the value of gravispheres method inaccuracy consists in neglecting the long duration of gravitational attraction of the Sun on planet phases, as well as of the planets on heliocentric phase of spacecraft trajectory.
The article presents the developed technique for direct determination of spacecraft trajectory (without applying gravispheres method) including Earth, Sun and Mars gravitational attraction effect on a spacecraft (as Newton’s dynamic model). Thrust vector direction is defined from solving variation problem with transfer duration as performance index (minimum time problem) applying necessary optimality condition in the form of Pontryagin’s maximum principle. Maximum principle application allowed simplify variation problem to the three points boundary value problem, solved numerically.Comparison of transfer performance indexes, i. e. duration and final spacecraft mass, obtained by the developed technique implementation, and application of gravispheres method is presented. In the last case on planet phases variants of parabolic velocity and hyperbolic excess velocity with value similar to the direct solution (without gravispheres method applying) is considered. Presented computation results revealed worsening of transfer duration and final mass in the case of applying gravispheres method vs. direct trajectory calculation (4-11% for duration and 2-6% for mass).
Keywords: interplanetary transfer trajectory, low thrust, method of gravispheres, optimization, maximum principle, response time problem
The research on influence of manipulator type and kind of control signal on pilot-aircraft system characteristics
Two types of possible feel system are considered. One of them is the displacement sensing where the signal transmitted to flight control system is proportional to the stick displacement. The other one is the force sensing where the output from the manipulator is proportional to the force. The analysis of pilot model taking into account two loops in neuromuscular system demonstrated the potentiality of the force sensing type of the feel system in decrease of the phase delay in pilot describing function. The ground-based simulation was carried out for the exposition of feel system types effects. For that purpose the pitch and roll tracking tasks were executed for the different controlled element dynamics, stick stiffness, for the side and central sticks. The experiments demonstrated that usage of the force sensing type of the feel system causes the decrease of pilot phase frequency response characteristics for all investigated variables. The effect is higher for the controlled element dynamics with improved flying qualities and smaller manipulator stick stiffness. The phase delay was decreased up to 120 deg in longitudinal channel and up to 140 deg in lateral channel. The increase of the spring stiffness decreases this effect up to 50÷700 in lateral and longitudinal channels. The usage of force sensing type of feel system causes the decrease of variance of error up 40÷700 in the both channel. Such effects took place for the side and central sticks too. The experiments demonstrated that in lateral channel pilot generates higher phase delay in comparison with longitudinal channel especially for the case of dynamics with deteriorated flying qualities.
Keywords: pilot-aircraft system, manipulator pilot frequency response characteristics, neuromuscular system
The solar sail, represented in the form of a thin rotating mirror film attached to a cylindrical rigid insertion, is considered. The flywheel is introduced to compensate the kinetic moment of the “rigid insertion—film” system. The author suggests to use albedo’s changes for creating the control moment. It will result in the structure elements’ kinetic moments vectors non-collinearity. As a result, the spacecraft will start rotating around the axis coinciding with the sum of these vectors. To study the advantages of the described control method, an assessment of the time and energy required for the solar sail reorientation in the case of a structure without compensating flywheel and with its presence is made. It is established, that the change in the angular velocity of the “rigid insert—film” system due to the tangential component of the light pressure force is 0.01% of the initial value. In view of this value’s smallness, a decision was taken to neglect it in the further investigation.
The shape of the film surface under the effect of the gyroscopic moment occurring while the sail surface albedo changing was established. The dependence of the film deviation from the plane of the rigid inserting from the angular velocity of the sail turn was obtained. The results of the conducted studies reveal that for a solar sail with a flywheel the turn time decreased by more than two times, and energy consumption decreased almost by factor of seven, compared to the solar sail structure without a flywheel.
Keywords: solar sail, the control of a spacecraft, change of the reflectivity
Innovation technologies in aerospace activities
Energy consumption growth continues worldwide and human activities negative consequences are manifested in ever-increasing degree. Electric power generation for the nighttime lighting leads to heavy consumption of hydrocarbon fuel. The negative consequences for the ecology can be reduced by dint of space technologies, using reflected sunlight for the nighttime lighting. The article analyzes spectrum of reflected Sun radiation from metallic coatings of various types of reflectors’, used in the space system for orbital Earth surface lighting. It is known by now that artificial lighting can disrupt at night photo-biological reactions of various living bodies, including humans. The short-wavelength spectrum region should be pointed out specially, featuring pronounced photo-biological effect. Thus, the author suggests to reduce the reflected Sun radiation flux in short-wavelength region (ultraviolet radiation and blue color), exerting the strongest biological effect. To ease the load on operator’s visual organs and reduce the undesirable effect on ecology, various metallic coatings are recommended for use in the orbital lighting system. Five types of metallic coatings for space reflector, namely aluminum, silver, titanium, copper and golden, were considered in the article. Reflectors with silver coating are suitable for ultraviolet radiation reduction (0.28–0.38 mcm) in reflected radiation, and for ultraviolet radiation reduction (0.28–0.38 mcm) and lighting by blue color(0.44—0.48 mcm) reflectors with copper and golden coatings can be used. At the same time, taking into account the entire set of requirements, titanium coating is optimal choice of reflector coating.
Keywords: orbital lighting, reflector, metal coating, spectrum, ecology
Optimization of Solar Energy Harvesting While Powering Wireless Methane Sensor from Renewable Energy Sources
Recently, there has been growing research interest in the application of wireless sensor networks (WSN) for monitoring of gas concentration at industrial facilities and in urban areas. Methane monitoring is one of the areas where WSNs can be used. In the absence of grid power, the operation of wireless methane sensors is determined by the capacity of their onboard batteries. The battery replacement or charging procedure can become a limiting factor for wireless sensor networks consisting of a large number of nodes or those located in difficult to access areas, such as networks used in some oil and gas projects. In this work, a hybrid power supply based on renewable energy sources is developed to increase the autonomous operation time of wireless methane sensors. The power supply converts solar and wind energy into electrical energy stored in supercapacitors. This paper describes two algorithms allowing increase the efficiency of supercapacitors charging in hybrid power supplies. The first one is a maximum power point tracking technique (MPPT) by finding what maximum power from solar panel can be achieved. According to the algorithm, maximum power point tracking is performed by changing the discharge time and comparing the output power of the solar panel before and after these changes. Load balancing mechanism ceases in case of obtaining a maximum power point. Rebalancing is performed by periodically changing the inductor discharge time. The second algorithm provides an efficient switching mechanism for supercapacitor charging. Both algorithms are applied to a power supply, which harvests solar and wind energy and is used for powering an autonomous wireless methane sensor.
Keywords: wireless methane sensor, hybrid power supply based on renewable energy sources, maximum power point tracking (MPPT) algorithm, supercapacitor charging switching mechanism
Instrument making, metrology, information and measuring equipment and systems
Optical and optical-electronic devices and complexes
While conducting experiments in the thermal wind tunnel it is necessary to measure the temperature distribution on the sample surface within the range up to 3000°C. This task is solved with pyrometry, allowing temperature measuring by equilibrium radiation’s registration of the studied object in visible or near infrared spectral range.
The complexity of the optical temperature measurement is caused by the absence of precise information on the tested model’s materials emissivity. Very often, these materials are novel, and information on their optical properties is inaccessible. Furthermore, the chemical composition of the sample surface may alter during the experiment and, in some cases, the surface destruction may occur. All these processes can change surface emissivity significantly. It should be noted, that emissivity change over the surface could appear rather non-uniform. Thus, it is necessary to use temperature-measuring methods, which do not require information on the tested object emissivity. As a rule, the tested objects are axisymmetric or flat bodies, and, therefore, the information on a temperature distribution along one line on the sample surface is sufficient.
The multi-channel spectrometer based on digital CCD camera was developed. It ensures a momentary acquisition of emission spectra along a certain line. The spectrometer consists of two lenses, slit diaphragm, diffraction grating and CCD camera with a lens. The radiation of the heated object is passing through two lenses and falls on diffraction grating. Lenses are combined to form the Kepler telescope scheme, producing the parallel beam. The third lens is used to form the spectral image of the slit on CCD array.
The developed multi-channel spectrometer was tested in TsAGI together with NRU MPEI. Tests proved the performance of the spectrometer and the ability to measure temperature distribution in the absence of emissivity value of the sample material.
Keywords: thermal aerodynamic installations, induction heating, plasma, noncontact temperature measurement, brightness pyrometry, spectral pyrometry, emissivity coefficient, temperature field
Information and measuring and control systems
The goal of the article consists in substantiation of aerial flying vehicles’ (UAV) control systems analysis with a view to the present ability of control interception and confidential information discredit.
The author developed the UAV control system’s information influence algorithm based on STANAG 4586 Edition No 3 Control System (UCS) Unmanned Aerial Vehicle (UAV) NATO Standardization Agreement 4586.
The presented algorithm determines possible channels for impact. The basic criterion for determining the system element as subjected to an external impact is existence of communications links, passing through the space points accessible for an intruder. To confirm the impact possibility, the supposed attack scenario is described using the suggested impact vector. The article considers various impact directions, which goal consists in intercepting control over the UAV, and reveals various merits and demerits of each of them.
The UAV control system information flows algorithm was developed. The revealed impact vectors were analyzed by the “strengths and weaknesses” method.
Several requirements to activities on UAV prototype model design management aimed at information security enhancement of the UAV control system were determined.
It was revealed in the course of the studies that the most effective impact on the control system of medium and heavy class UAVs is the impact on the systems of spatial positioning and navigation.
Keywords: unmanned aerial vehicles, information security, cyber-attack, robotics, counteraction to unmanned aerial vehicle, attacks, telecommunication system, security
Radio engineering and communication
Radio engineering, including TV systems and devices
Transition to the electronic representation of electric circuits in the existing information support systems does not ensure significant time gain while forming diagnostic information in the form of electric circuits’ fragments. It restricts the information support systems’ abilities on reducing duration of technical diagnostics and recovery of electronic equipment of complex technical systems. The time of complex technical systems recovery can be reduced by decreasing the time necessary for forming diagnostic information in the form of electric circuits’ fragments.
The proposed method contributes to the recovery time of complex technical systems reduction by improving the efficiency of information support automation means of the diagnostic systems. This method allows forming diagnostic information in the form of electric circuits’ fragments based on their structural and functional properties’ description in object notions and terms of natural language. The presented method is based on the mathematical apparatus of the theory of sets and relations, predicate calculus, the theory of formal languages and grammars.
There is a good reason to consider the obtained results as methodological basis for the modern information support systems for technical diagnostics, oriented on applying an electronic folder of the product as an information base of such systems. It contributes to functionality enhancing of the relevant information support systems.
Implementation of the proposed method allows repeatedly reduce the diagnostic information formation time of electronic equipment electric schemes in the form of fragments and to decrease the recovery time of complex technical systems up to 14%.
From a practical point of view, the proposed method ensures a time reduction of the diagnostic information formation. This method creates a formalized base for the architecture development of information support system for technical diagnosis process. The aggregate of the obtained results is aimed at electronic equipment models and methods representation on account of the necessity to form diagnostic information in the corresponding application domain.
This work is a starting point for further research in the field of process of information support of the complex technical systems’ technical diagnostics.
The developed method of the diagnostic information formation while complex technical systems recovery is based on implementation of the aggregate of models and methods, ensuring concordance of conceptual and schematic and graphical representation of radio electronic equipment based on elements’ patterns of electric circuits.
Keywords: diagnosis process, conceptual model, radio electronic equipment recovery
In the conditions of electromagnetic radiations impact, various by the nature of emergence and nature of distorting influence, for increase of autonomy of robotic systems from positions of information transfer it is necessary to solve two problems: to provide authentic transfer of important and technological information and to distinguish the transferred information distortion reasons.
The Methods of identification interference, is based on the solution of a problem of classification. As the signs describing distorting influence of hindrances, estimates of random variables which characterize are used, how many time each important and technological team, taking into account the compelled repetitions was transferred, a Fisher’s linear discriminant strengthened by Bagging algorithm is chosen as the qualifier.
The methods of identification interference operating in the communication channel of robotic systems, including three main points is developed:
– formation of a vector of signs of distorting influence of hindrances;
– identification of a vector of the signs characterizing distorting influence of hindrances;
– the alarm system to the operator on management point.
In article offers on realization of a technique of identification of hindrances in intellectual system of recognition of the transferred information distortion reasons are presented.
Application of the developed methods of identification interference in common with way of non-uniform error-detected coding allows to localize the information distortion reason in a communication channel and to exclude possibility of passing of unreliable information.
The methods of identification interference can be realized in intellectual system of recognition of the transferred information distortion reason and to be a segment of system of support of decision-making.
Keywords: robotic system, information broadcasting channel transmission, electromagnetic interference, identification of interference, a Fisher’s linear discriminant
Antennas, SHF-devices and technologies
Effectiveness evaluation results of multiple-beam self-focusing adaptive antenna arrays of radio-electronic systems
The goal of the paper consist in Effectiveness evaluation results of multiple-beam self-focusing adaptive antenna arrays of radio-electronic systems.
The paper considers information radio-electronic system searching for radiation sources in conditions of complex signal-jamming environment, characterized by a priori uncertainty relative to their number and spatial position. The radiation sources’ signals feature overlapped energy spectra. The search is performed by the adaptaion results of the multiple-beam self-focusing adaptive antenna arrays as a part of antenna block of information radio-electronic system. The adaptation result represents separate estimations of the radiation sources signals’ amplitude-phase distribution at the aperture of the radio-electronic system antenna block. It allows form separate spatial channels for receiving the signals from radiation sources according to maximum criterion of signal/interference + noise ratio. The signal detection is based on Neyman-Pearson criterion by sampling results analysis, formed at the output of each spatial receiving channel. Estimation errors occurrence of vector of parameters of the multiple-beam self-focusing adaptive antenna arrays results in signal/interference + noise ratio decrease in spatial receiving channels, and, as a consequence, to efficiency reduction of radio-electronic systems by criterion of “correct detection probability”. Evaluation of the total error’s fluctuation value of the vector of parameters of the multiple-beam self-focusing adaptive antenna arrays was executed using a well-known estimation technique, as well as according to the simulation results of the considered adaptation algorithms. The obtained results revealed the parameter, mainly affecting the fluctuation value in evaluations of amplitude-phase distribution formed according to the results of the multiple-beam self-focusing adaptive antenna arrays adaptation. This parameter is angular misregistration of the radiation sources between each other. At keeping herewith the equality of the radiation sources’ angular positions the fluctuation error value would be affected by their number and bandwidth value of the self-adjustment closed loop of the multiple-beam self-focusing adaptive antenna arrays.
Keywords: multiple-beam self-focusing adaptive antenna array, signal detection, mutual interference
The goal of the work consists in optimization method development of decision-making on technical servicing (TS) of adaptive phased antenna array (APAA), including the structure of works, periodicity and TS duration. The decision-making on servicing and recovery is realized in the framework of the unified APAA technical conditions monitoring and control complex, which is developed using reliability characteristics’ modeling, and internal control systems abilities.
The research methodology accounts for the availability of the APAA hardware and software components and uses modern logical-and-probabilistic methods for the reliability analysis of the systems under restoration, based on reliability flowcharts. The problem of reliability characteristics optimization (probability of no-failure and readiness factor) is formulated as the basic method for adaptive TS. Its practical realization is based on implementation of numerical methods for solving an optimization problem.
The author suggests a design method of a complex for monitoring and control of technical state of prospective APAAs based on complex use of built-in monitoring data and numerical solution of optimization problem. To that end, the APAA reliability model, accounting for its specificity as highly reliable information system and including the redundancy specifics, was developed successively.
This complex based on practical use of the reliability model allows compute the content and structure of TS complex, which will ensure the optimal combination of duration, scope, TS periodicity and APAA reliability characteristics (readiness factor optimization).
The obtained results can be applied in the field of reliability increasing and operational life extension of APAA and radar stations in total.
Keywords: adaptive phased antenna array, technical servicing, optimization, monitoring, controllability
Low – profile wideband antenna with improve pattern, using artificial magnetic conductors (AMC) surface ground
Active antennas’ array are the main type of perspective aviation and space radar complex of different appointment, with the wideband of working frequencies, consist of vibrator systems, which located over the metal screen. One of the important parameters either for aircrafts and for space systems - is profile height of antenna. As for aircraft, it is important to protect aerodynamics of airplane, for space systems, it is important for compact location antenna inside fairing.
The perspective method of lowering the profile height is using periodical microwave composite structures with parameters of artificial magnetic conductors (AMC).
AMC structures working in the quasi-static field (wave length more than period of structure) and defined by equivalent parameters in quasi-static approximation. The tangent component of magnetic field on AMC structure is equal to zero, and reflective coefficient is +1.
The paper presents the composite L – a band structures to improve characteristics of antenna’s system. AMCs have been chosen as design concept of the baseline array element due to the significant size of reduction they can offer.
Although the majority of satellite communications operates at frequencies above L-band, there are interesting opportunities for satellite communications in the very high frequency (VHF)/ultra-high frequency (UHF) spectrum.
A standard printed square patch has been selected as reference low-profile element. The binary patch emitter was chosen to improve the directive characteristics of antenna. Desiged antenna has the lateral dimension of 14 millimeters (0.093λ0), staying wave ratio below 2, and directivity 10 dB, working band of frequency is 40%. Traditional case of location vibrator over AMC surface compared with developed antenna.
Keywords: wideband antenna, low – profile antenna, artificial magnetic conductor (AMC), directivity pattern
Radiolocation and radio navigation
Solution of a problem on object’s type recognition based on antennae's directional pattern as a feature
The goal of the article consists in object type recognition algorithm developing, based on antennae system’s direction pattern.
To achieve this goal the authors suggest the distance function use, which determines the difference between various radiation pattern cuts of the antennae systems. The decision-making on the type of the object under recognition is performed using Student criterion. The algorithm proposed in the article allows the object recognition performing based on directional diagrams with the ability of the significance level variation. Based on the presented data, the authors draw inference on the possibility of the object type recognition problem solution by applying the directional pattern of the antennae system, constructed according to the measurement results, as a recognition feature.
The proposed algorithm allows perform the object type recognition based on antennae directional pattern, constructed according to the measurement results. The problem is topical, notwithstanding the difficulties associated with multiple beam structure of directional patterns of antennae systems. Addition of new recognition features allows describe the object in more details and increase the probability of the object recognition correctness according to features aggregate.
Keywords: directional pattern, recognition, features, significance level, hypothesis
Possibilities of application of multifrequency quasinoise signals in the conditions of conducting radio engineering intelligence by the opponent
The purpose of article is assessment of reserve and consideration of a possibility of application of multifrequency quasinoise signals in reserved radio engineering systems in the conditions of conducting radio engineering investigation by the opponent.
On the basis of a mathematical model of the broadband multi-frequency quasinoise signal synthesized with use of conversion of Jacobi-Angera in article the method of formation of the considered broadband signal realized on the modern element basis is considered. It is shown that generation of a multi-frequency signal is carried out on the basis of the harmonic phase shift keying of basic narrow-band accidental process which is rather just realized in practice with normal distribution of the instantaneous values, by expansion in a row on Bessel functions of the first kind.
The multi-frequency quasinoise signal described in article in the form of a pica of a body of uncertainty in the required intervals on time of delay and on the Doppler shift on frequency is close to a noise signal. For certain initial conditions — equality of a band of the initial narrow-band accidental process and frequency of phase harmonic shift keying, the range of a multi-frequency quasinoise signal becomes continuous and shumobodobny.
The dependences of assessment of an index of Lyapunov and probability of disclosure of a signal structure on frequency change of phase shift keying of MCh KSh of a signal calculated by means of simulation modeling in case of the modified interpolation method allow to conclude that in case of increase in frequency of phase shift keying there is a rise of values of the considered index and reduction of probability of disclosure of structure of a signl. It occurs in connection with proportional broad banding of frequencies of the occupied MCh KSh a signal. Application of multi-frequency quasinoise signals of big duration and occupying the considerable frequency band will allow to increase reserve of operation of radar station in the conditions of guiding by the opponent of radio engineering investigation, saving at the same time high resolution capability on range and speed.
Keywords: noise radar technology, multifrequency quasinoise signals, reserve of radio engineering systems, probability of disclosure of structure of a signal
Informatics, computation engineering and management
The minimum-time problem of the correction of the movement of the satellite is considered in this paper. The orbit of the spacecraft is assumed to be circular. Correction Correction is carried out by means of low-thrust engines capable of generating acceleration in the radial and transverse directions. Controls are assumed to be ideal and impulsive. It is proved that the initial problem can be reduced to the minimum-time problem for the linear non-stationary system with discrete time and limited control.
The solution of the minimum-time problem for a non-stationary linear discrete-time system is based on the use of the class of sets of 0-controllability — such sets of states of the system from which the origin can be reached in N steps, starting with step k. For the case when the set of feasible controls is a strictly convex body with non-empty interior, an analytic description of the sets of 0-controllability is constructed: each set can be represented as the algebraic sum of strictly convex sets, i.e. it is also a strictly convex set.
The lemma on the uniqueness of the expansion of the boundary point of the sum of two strictly convex sets is proved. It is possible to construct a criterion for the optimality of the trajectory of the system and control on the basis of this lemma. The trajectory and controls is connected with each other by a system of conjugate vectors. The obtained results are formulated in the form of the maximum principle. It is also proved that the initial state of the conjugate system is a normal to the set of 0-controllabillity, whose boundary point is the initial state of the control system. For the case, when a set of feasible controls is an ellipsoid, an explicit form of optimal control is proposed.
It is proved that if the initial state is an internal point, then the maximum principle becomes incorrect, and optimal control is not unique. Nevertheless, an algorithm is proposed that makes it possible to reduce the given case to the considered one.
The obtained theoretical results are applied to the problem of correcting the satellite’s orbit. The results of the calculations are given in the table.
Keywords: ideal impulse correction, linear discrete-time nonstationary system, minimum-time problem, maximum principle
The purpose of this article is database modelling for real-time special-purpose systems.
It is shown that the use of the all-purpose client-server databases for solving the air force and air defense tasks leads to poor query performance. In some cases, the use of more simple distributed databases allows reducing the query time by 90%, but the amount of data does not allow using them as a single solution.
Given the limitations of the scientific and methodological methods for evaluating the effectiveness of the database, the article offers a method of modeling the database, which allows to parametrize data and evaluate database performance. Database modelling helps to carry out the management structure of the database.
Database modeling is made by mathematical methods of queuing theory, the DBMS performance criteria are based on the average execution time of queries to the database.
This article provides a method for constructing an optimal database structure when using a distributed inhomogeneous database for processing of data with a wide range of characteristics. Restrictions in optimization problem are based on database load. The optimization problem is reduced to the Boolean satisfiability problem — the problem of determining if there exists an interpretation that satisfies a given Boolean formula. The variation of the branch and bound algorithm is used to solve the SAT-problem.
It is shown that the design of real-time database management system based on database modeling techniques can significantly increase the performance of data processing.
This article provides a model of a database management system as a queuing system.
It is shown that the application of optimal control database structure allows you to double the capacity in dealing with real-time heterogeneous tasks.
Keywords: DBMS design, queuing theory
Mathematical support and software for computers, complexes and networks
The paper considers the problem of fast bilateral filtering of aerial photographs, which allows eliminate small-sized noise and interference, while maintaining sharp boundaries of the objects, necessary for the initial frame processing. Hence, the emphasis is increasing the rate of bilateral filtration as an important stage of the frames processing and restoration. To solve the problem, a fast method of bilateral filtering based on decomposition into independent spatial filters, which allow aerial photographs filtering by several processes simultaneously is considered.
To achieve the processing speed of the bilateral filter, a method based on decomposition into recursive Gaussian spatial filters is proposed. Unlike the ordinary bilateral filtration, the presented filter can be parallelized. According to the method, N sets of linear independent filters (components) are computed based on N ranges of pixel intensities on the processed frame. The number of ranges is user-defined (from 2 to 255). The remaining components are computed by bilinear interpolation from the already obtained components. Each component requires computation of two filters, rank and spatial. Hence, the computational complexity of the method will depend on the calculation of the spatial filters in the N components.
The Gauss kernel approximation proposed by Deriche are used in the article for the spatial filters quick computing. This allows increasing the rate by several times, using the pre-calculated filter coefficients that specify the form of the Gaussian function, instead of costly computing the Gaussian distribution of each pixel in the frame. The coefficients are calculated from the infinite impulse response of the Gaussian filter, which can be represented by a recursive sequence with constant coefficients.
Thus, the article reduces the time of bilateral filtration due to bilinear interpolation over N independent spatial filters. The time for calculating the spatial filters is reduced due to the use of the fast Gaussian filtering method by Deriche based on constant coefficients. The article also uses parallel calculation of independent components of the proposed method of bilateral filtration. The steps, proposed in this article allow get real-time results.
Keywords: aerial photography, bilateral filtering, recursive Gaussian filter, parallelization
Computing machinery, complexes and computer networks
Many realizations of wireless technologies found application in various technology areas. Intensive search process for the trends of wireless systems and units implementation, allowing rapidly gain an appreciable economic effect, commenced in aviation industry. Expert judgments reveal that wireless technologies implementation will allow develop highly efficient aircraft control, monitoring and diagnostic systems of new generation, reduce weight and size by 20–40%, increase reliability and reduce system’s maintenance cost by 5–8 times. The onboard wireless sensor network application in onboard systems, not critical for the flight safety, can be considered successful.
Wireless technology application in such mission-critical systems as flight or engine operation control is associated with a number of contradictory requirements. Thus, the reliable data transfer between network nodes at a speed of 30–100 Hz and accounting for the signal decay requires transceivers power increase onboard an aircraft. However, onboard wireless units power supply from standalone power sources, prevention of radiation effect on neighboring radio channels and electronic equipment requires low energy consuming.
The article analyzes materials of foreign firms on studying the possibility of wireless systems based on protocols of IEEE 802.11 standard application onboard an aircraft.
The results of studying the possibility of narrow-band wireless data transmission at the frequency of 868 MHz in wireless aircraft engine automated control system are presented. Experiments were conducted on laboratory complex CIAM with various variants of central radio module shielding by fuselage, and wireless sensor shielding by the engine nacelle, and various distances between them.
The article shows that with complete screening simulation and distance of more than 13 m the information channel errors occurred, and from the distance of 15 m complete loss of connection took place. The wireless information channel failures were not observed for the other variants of shielding in the survey distance of 30 m.
The main problems of applying wireless technologies in the aircraft onboard systems are as follows:
– ensuring reliable wireless data transmission with the required rate and at a predetermined distance; ensuring electromagnetic compatibility (EMC) of wireless sensor network with onboard avionics systems under tough operating conditions on and aircraft and engine;
– reducing power consumption of wireless electronic devices for control and monitoring systems, as well as the system for technical condition diagnostics of an aircraft and engine.
Keywords: wireless aircraft engine control system, wireless sensor network and the sensors, transceiver, radio channel
This paper is devoted to various aspects of wireless sensor networks (WSN) self-organization. The WSN specific features distinguishing them from a more general class are revealed. These features are as follows: directions of data flows, nodes mobility and limited resources. The article formulated the main WSN performance indicators, such as network lifetime, reliability, scalability and message transmission rate. With reference to the WSN, the following principles of self-organizing systems developing are considered: local interactions rules that achieve global goals developing; ceasing a perfect interaction seeking; implicit coordination application; reduce the information volume on the system state; developing the protocols adapted to the changes. The article substantiates the importance of the general self-organization mechanisms (positive and negative feedback, nondeterministic behavior, nodes interaction) in various WSN functioning protocols and methods, such as MACA, S-MAC, PCM, SMACS, SFSN, flooding, AODV, OLSR, hierarchical routing. Based on the analysis, the conclusion was made on the impossibility of developing a fully functional WSN with the agreed values of its performance indicators without developing a unified method of the WSN functioning based on the self-organization principles.
Keywords: wireless sensor network, self-organization, performance indicator, protocol, duty cycle, multiple access to channel, routing
Mathematica modeling, numerical technique and program complexes
The problem of increasing the efficiency of the operation of the object of warehouse logistics in the example of a warehouse of aircraft parts is considered. As performance measures are considered indicators adopted in queuing theory, characterize the performance and loading facility. To solve the problem developed simulation system based on the integrated use of the conceptual, analytical and simulation methods. The simulation model of problem analysis is an important part of the simulation system, it allows to investigate low-level operating processing processes, evaluate alternatives, develop recommendations for the modernization of processes. The model of problem analysis is implemented with the use of a hybrid approach. It is developed on a modular basis, which allows one to integrate within the framework of one model elements described by heterogeneous mathematical schemes. The approach of modeling the input stream of a complex structure has been developed, the requests of which undergo multiple splitting, corresponding to the transition from one technological process to another. Application of the developed approach to modeling input stream of the detailed presentation level, makes it possible to configure both deterministic and random input with group heterogeneous requests. The approach allows to obtain the following parameters of the functioning of the object warehouse logistics: the waiting time and the start of the service pack; delays inside the pack; packets delay, the number of requests in the system. The dynamics of changes in these parameters is necessary tracked, since the group receipt of requests significantly worsens the performance of the system in comparison with the general arrivals of the same average intensity. Unlike existing approaches, the proposed approach assumes the representation of the input stream by a set of interrelated agents, which allows modeling the input stream with group heterogeneous requests. The model of input stream is implemented using the agent-based approach of simulation modeling. The algorithms of generating initial data for modeling of the random input are developed. Simulation experiments were performed: estimates of workload and downtime was obtained; the effective technology of unloading pallet was identified; the limiting capacity of the acceptance zone was calculated.
Keywords: simulation system, hybrid approach, agent-based approach, pattern, state diagram, identification, the criterion of consent, experiment
Supersonic aircraft's welded compartment model development with account for constructive-technological scheme
The article describes the approach to modelling welded sections of supersonic aircraft with account for their constructive-technological schemes. It based on possibility of accounting for the sequence of factors at finite element analysis, such as, residual tensions caused by welded zones shrinkage, model variability of material sections and their stiffness, etc. The current state of a problem regarding developing of mathematical models of welded structures and their subsequent optimization is analyzed. The proposed method of system synthesis of a section structure considered an order of welding assembly of section design. The developed finite element model of a welded compartment with account for the residual tension is based on modification of a method of forces better known as an “inherent strain method”. This method comprises some thermal-affected zones of a welded section initial design for obtaining pre-tensed state of a compartment. The modeling results revealed distribution changes of operational deflections of the section panels when the residual stress was introduced previously by the bearing. Application of the developed model allowed obtain at a time the stress-strain state dependencies of the welded sections fr om the design data and optimize the top panel thickness. The developed aircraft’s welded compartment model allows evaluate the effect of constructive-technological scheme on its stress-strain state. Applying this model the authors will solve various optimization problems containing requirements and restrictions to allowable stresses, such as deflections magnitude, buckling modes, weight lim it, etc. The solution of such multifactorial, multi-parametric optimization will appreciably reduce timing for a product study and development.
Keywords: supersonic aircraft, compartment, welded structures, welding technology, residual strain, finite elements method, finite element model
Neural network based semi-empirical approach to the modeling of longitudinal motion and identification of aerodynamic characteristics for maneuverable aircraft
The simulation problem for longitudinal motion of a maneuverable aircraft is considered including identification of its aerodynamic characteristics, such as the coefficients of aerodynamic axial and normal forces, as well as the pitch moment coefficient. This problem is solved in the class of modular semi-empirical dynamic models that combine the possibilities of theoretical and neural network modeling.
This approach differs significantly from the traditionally accepted method for solving problems of this class [6-8], based on the use of the linearized model of the disturbed motion of the aircraft and using the representation of the dependencies for the aerodynamic forces and moments acting on the aircraft in the form of their expansion into a Taylor series, leaving in it, as a rule, only members not higher than the first order.
Accordingly, the solution of the identification problem with this approach is reduced to reconstructing from the experimental data the dependences describing the coefficients of the Taylor expansion, in which the derivatives of the dimensionless coefficients of the aerodynamic forces and moments with respect to the various parameters of the motion of the aircraft are determining.
In contrast, the semi-empirical approach realizes the reconstruction of the relations for the force coefficients and moments as some whole non-linear dependencies on the corresponding arguments, without resorting to their series expansion and to linearization, i.e. the functions themselves, represented in the ANN-form, are evaluated, and not the coefficients of their expansion in a series. Each of these dependencies is implemented as a separate ANN-module, built into a semi-empirical ANN-model. Derivatives etc. if necessary, can be found using the results obtained during formation of the ANN-modules for the coefficients of forces and moments within the semi-empirical ANN-model.
A mathematical model of the longitudinal motion of a maneuverable aircraft is derived, which is used as a basis in the formation of the corresponding semi-empirical ANN-model, as well as for the generation of a training set. An algorithm for such a generation is proposed, which provides a fairly uniform coverage of the possible values of state variables and controls for the maneuverable aircraft by training examples. Next, a semi-empirical ANN-model of the longitudinal controlled motion of the aircraft is formed, including the ANN-modules realizing the functional dependences for the coefficients . In the process of learning the obtained ANN-model, the identification problem for these coefficients is solved. The corresponding results of computational experiments characterizing the accuracy of the formed ANN-model as a whole, as well as the accuracy of the solution of the problem of identification of aerodynamic coefficients are given.
Keywords: nonlinear dynamical system, aircraft longitudinal motion, aerodynamic model identification, semi-empirical model, neural network learning