2016. № 87
Deformable body mechanics
In the paper variability of Poisson's ratio for the different hexagonal crystals under hydrostatic pressure is analyzed theoretically. As a result, all extreme values of Poisson's ratio are determined analytically. Special attention is paid materials with negative Poisson's ratio. Seven hexagonal auxetics at zero pressure (crystals with a negative Poisson's ratio) MoS2, Zn, Be, BeCu alloy (2.4% at.Cu), TiB2, C7H12, MnAs are identified. Variability of Poisson's ratio is analyzed for these crystals at zero pressure and two nonauxetics at zero pressure (graphite and SiC). Numerical values for all еxtrema of Poisson's ratios were obtained. Auxetic surfaces (the surface of the zero Poisson's ratio) were plotted for all auxetic hexagonal crystals and two nonauxetics (graphite and SiC) depending on the crystal orientation and the hydrostatic pressure. It is shown that the seven hexagonal partial auxetics MoS2, Zn, Be, BeCu alloy (2.4% at.Cu), TiB2, C7H12, MnAs can become complete auxetics under certain pressures. Partial auxetics are crystals whose Poisson`s ratio can change the sign with the change of orientation, while complete auxetics are crystals, in which Poisson's ratio is always negative regardless of orientation. Analysis of the pressure influence on Poisson`s ratio shows that crystals MoS2, TiB2 and MnAs are auxetics in the whole range of pressure values at which the crystal is stable. Auxetics Be, BeCu alloy, C7H12 and Zn have one nonauxetic zone in a range of pressure variation. The crystals of graphite and SiC, which are nonauxetics at zero pressure, also become partial or complete auxetics at some negative pressure (at isotropic stretching). As a result, numerical and analytical analysis shows that all hexagonal crystals may be partial and complete auxetics depending on the values of hydrostatic pressure. It has been found that Poisson ratio corresponding stretching in the  direction and the transverse deformation in the direction, approaches -1 if the negative pressure tends to the limit of stability of MoS2, Zn, Be, BeCu alloy (2.4% at.Cu), TiB2, C7H12, MnAs, graphite and SiC crystal.
Keywords: hexagonal crystals, auxetics, pressure, elastic properties
Aeronautical and Space-Rocket Engineering
Aerodynamics and heat-exchange processes in flying vehicles
Developed turbulent boundary layer contains organized vortex structures, which determine various physical properties of the flow. Recent experimental and numerical studies confirm the existence of coherent structures. The flow in the developed turbulent boundary layer is well described by Navier-Stokes system of equations. However, solution of these nonlinear equations presents severe difficulties. One of possible alternative approaches to solve these equations describing the developed turbulent boundary layer is a waveguide model, where a hypothesis for the equality by order of tangential stresses at the side and maximum value of the least damping mode of Tollmien-Schlichting waves decrement value. This hypothesis can be expressed by the equation , which determines the change of the thickness of the boundary layer downstream. Here δ** is pulse thickness loss; and — damping mode of spectral problem least eigenvalue for the Orr-Sommerfeld equation at the turbulent longitudinal velocity profile in the boundary layer; τw — the value of tangential stresses at the side; a — constant determined from the comparison with experimental data.
To do it we, firstly, solve the spectral problem at non-uniform grid for Tollmien-Schlichting equation for vertical component of speed. Here we used numerical integration to transfer differential equation to difference form of second order of accuracy. Such approximation gives us standard matrix, which is solved in «Mathematica» package. Then we will find the δ**(x) dependence, inserting it into the formula, and obtain a. This hypothesis allows separate out the coherent structure and close the moment equations system, determining the average coherent pulsations dynamics and stochastic component spectral density. This work is aimed at the test of this hypothesis.
Keywords: incompressible viscous fluid, turbulent boundary layer, Orr-Sommerfeld equation, the wave of the least damping mode, non-uniform grid
On an approach to hypersonic vehicles development projects feasibility qualitative and quantitative evaluation with regard to aeromechanics
The issues of high-speed aircraft design and development methodology with regard to feasibility of various projects are considered in the paper. The well-known foreign projects are exemplified as a subject of research to detect the destructive factors affecting the hypersonic flying laboratories projects. Methodological working out of the issue concerning hypersonic vehicles development projects feasibility quantitative and qualitative evaluation to design corresponding industry methodologies without considering specifics of engine unit workout. The time of transition from laboratory research to practical industrial production was accepted as a project feasibility quantitative measure, which can be evaluated a priori with both algebraic relation and using ordinary differential equations, such as works by U.V. Chuev and S.M. Eger, which elements are introduced in the presented paper as scientific research tools. The problem of the high-speed flying vehicles working-out cycling is associated with parameters margin evaluation for ambiguous and non-stationary aero-physical processes.
Considering that with high-speed flying vehicles flight speed increase (Mach number) the share of non-stationary effects and their specific energy performance increase in the overall volume of utilization flights, the paper observes the corresponding aero-mechanical effects, drastically affecting the feasibility of the project. As a rule, with mode change (in the case under consideration — the stream pattern change) some non-steady effects occur, associated with either loss of controls effectiveness and dynamic system instability of flying vehicle — controls system, or with higher overloads. The latter is illustrated by numerical calculations of aerodynamic performances results, obtained by the authors. To calculate either stationary or non-stationary aerodynamic performances a program for obtaining numerical solution of complete non-stationary Navier-Stokes equations developed by the authors was used. Computational experiments were carried out in the framework of perfect gas model with laminar flow mode in moving coordinates. To determine damping and anti-damping characteristics associated with high-speed flying vehicles flight stability and instability the conjugate problem of flight dynamics and non-stationary aerodynamics was being solved.
The attainability of the goal set to flying vehicle project and the degree of its feasibility are associated with the degree of studies and the extent of fundamental, forecasting, as well as scientific and applied research, required before starting corresponding development effort.
Keywords: aerodynamics, forecast, non-stationary characteristics, numerical methods, vehicles, supersonic flight, research work
Computational modeling of applied tasks of helicopter aerodynamics based on non-linear vortical model of a rotor
Computational modeling and problem solving in the field of aerodynamics -so called ‘computational experiment’ recently has become more and more actual in design of aircrafts and its modernization. This happens, first of all, due to rapidly growing possibilities of computing techniques, which give a chance to implement mathematic models, adequately reflecting complex physical processes of flow-around of aircrafts’ different lements
Using of modern methods of computational modeling in problem solving for aircraft aerodynamics lets amplify and partly even replace hard expensive experiments in a wind tunnel and flight tests with security risks.
The article contains review of possibilities and demonstration of practical examples of using non-linear blade vortical free-wake model of helicopter rotor and its software algorithmic implementation created in Helicopter Design Department of MAI.
Model and software provide an opportunity to calculate parameters for main, tail and propulsion helicopter rotors and their combinations considering interference, getting full aerodynamic characteristics and rotors’ flows schemes, including special regimes, when vortical wave is significantly non-linear.
Model and software are used to solve various applications tasks of helicopter rotors’ aerodynamics. Research is carried out for the benefit of industry players. The results of research are included into academic activity of Helicopter Design Department of MAI.
Keywords: non-linear vortical model, software implementation, helicopter rotors, vortical wake, flow visualization, aerodynamic characteristics, rotor geometry, rotors’ interference
Design, construction and manufacturing of flying vehicles
The paper presents the results of numerical study of the impact of the main rotor blades individual control by their pitch angle cyclic variation to reduce thrust pulsations transferred to the main rotor hub, resulting in negative effect of the helicopter structural elements, crew and passengers. The study consists in developing the methodology and mathematical model of blades azimuthal control at blade frequency and its overtones.
The authors carried out numerical studies of the thrust variable loads caused by non-stationary flow around main rotor blades transferred to the rotor hub at higher relative flight speeds. The thin lifting surface scheme was used to model the flow through the blades process. The authors performed an analysis of varying loads and educed the amplitudes of their deviation from the conventionally controlled main rotor thrust without higher harmonics control. Rotor blade pitch higher harmonics control algorithms were developed, which allow reduce thrust the main rotor pulsations at thrust average value.
Computational studies showed that rotor blade higher harmonics control allows reduce the level of variable loads. The required blade setting variation herewith comes up to ±0.2 degrees, which conforms to maximum additional displacement of the control rod realized in practice with the value of about 1 mm.
Keywords: vortex theory, helicopter rotor, variable load, vibro g-load, control algorithms
Elements of Method of plan view formation on the layout scheme synthesis stage of front-line aircraft constructed by the normal balancing scheme and with internal cargo bays
This article describes the main elements of a method, which allows to generate the aircraft plan view with a minimum number of iterations (revisions after aerodynamic and weight calculations results). The elements of the method are described by the example of the front-line aircraft layout scheme development (synthesis), front-line aircraft model (with two engines and internal cargo bays) made by the normal balancing scheme. The synthesis is carried out on the basis of pre-defined design parameters, constraints, and solutions, which are set by the designer, based on parametric relations and statistical relationships analysis.
Designer need to determine the so-called «Layout Field» on the stage of aircraft layout scheme synthesis. «Layout Field» is a plan view on the aircraft geometric shape formation initial stage. Plan view determines the load-bearing capacity and area chart, which defines aircraft volume and wave component in the aerodynamic drag increase.
Aircraft plan view formation — is, traditionally, the first stage of geometric shape design. At the beginning of this stage constructor needs to determine:
— The area of the plan view.
— Restriction on the transverse dimension of the plan view (wingspan), if available.
— A limit on the size of the plan longitudinal view (aircraft length).
— Limit on the width of the fuselage side ( distance of the wing chord side).
— The position of the wing along the length of the aircraft.
— The position of the center of mass (to a first approximation).
— Variants of the cargo bays, air intakes and engines location (interconnected with each other).
— Engines position along the length of the aircraft.
— Air intakes position along the length of the aircraft.
— The parameters of the horizontal tail (area and shoulder).
— The position of the aerodynamic focus and the center of the sail of the plan view.
After that, the designer checks the feasibility of the given boundary conditions.
Feasibility of the boundary conditions сhecking is carried out to control the results of the method. Checking algorithm is reduced to compare results, which were obtained at this stage, whit previously determined design parameters. If the boundary conditions are not met, the designer performs a variation of decisions determining the schemes synthesis, beginning, in order, with the least important, up to the boundary conditions feasibility. If it’s impossible to fulfill one or more conditions, this variant of the scheme is not considered further.
Due to verify the boundary conditions feasibility, the possibility of reducing the number of unnecessary options is realized at this stage, and thereby this will reduce labor and time for further analysis.
After checking the boundary conditions feasibility, the designer carries out a further scheme synthesis. There is a study of the longitudinal and cross sections, layout elements placing, mass and aerodynamic performance calculation.
Keywords: layout, area, parameter, synthesis, compare
Computer aided design in the modeling mode of technological processes producing the elements of the flying apparatus constructions
Pipes with different diameters and various joints as well as pipes with nipples having huge diversity which are composed of the pipes materials are widely used in aircraft construction design. In order to ensure performance characteristics regarding the pipes joints and their parts having wingtips, stringent requirements on tightness, strength, vibration resistance are imposed to guarantee interchangeability and manufacturability. This article is dedicated to a process modeling concerning the development of tubular joints of aircraft constructions by deforming one of the joined tubular parts using pulse magnetic field. In produce of new equipment construction the meticulous development test of technological processes is required, especially when impulsive methods of processing of materials are applied. For this purpose, computer modeling of the deformation process using the modern resources of software is applied.
By using magnetic pulse formation process, it is possible to concentrate the deforming pipe, control according to the parameters at the required zone and the mentioned process provides tight joints. At the same time, it requires precise technological development procedures. Presented results of work on developing method modeling the high-speed mode of the process of producing a magnetic pulse of some tubular structure elements of flying apparatuses.
For this, the solid models of pipeline samples and inductor are developed at first using computer aided design. Solid modeling of construction parts was carried out by using Autodesk Inventor software and simultaneously the HyperMesh package was utilized for generating small grids as well as the geometrical parameters of 3D solid models. To estimate the possibility of formation of tubular part compounds and their welding’s on program LS-DYNA, the modeling process of magnetic-pulse deformation is performed by varying the parameters of the magnetic field generated by the pulsed pressure, geometrical parameters and position of tubular work pieces and characteristics of their materials. By obtaining the solutions, it is possible to determine the final deformation of work pieces, stresses arising in the areas of compounds.
The data obtained from the modeling process allow for developing the required control parameters of parts deformed by pulse magnetic field, designing instruments and forming the required high quality tubular joints of aircraft structure.
Keywords: pipes, dissimilar materials, welded joints, Permanent joint, magnetic pulse deformation, forming with magnetic pulse field, high speed deformation, computer aided design, solid model, 3D modeling
The efficiency of space solar electric power station with application of a laser channel of energy transfer is analyzed as well as a concept of control system of this laser channel of energy transfer behavior of such electric power station. The necessity of development of a demonstrative space solar electric power station on the basis of present space-rocket and optical and electronic technics is shown.
The technology of energy transfer by means of laser radiation has been recently significantly developed due to the fact that efficiency coefficient and power of developed lasers for the last 10 years have dramatically increased because the divergence of laser radiation is too small and it allows creating ground receiving areas of energy with dimensions that are on several degrees lower than in case of using microwave radiation. Moreover, ground receiving photo-integrated devices can operate from laser and solar radiation, so the efficiency of overall solar electric power station increases.
Solar space electric power stations unlike nuclear-thermal ones do not have unsolvable physical and technical problems, but have some financial and technical difficulties which can be solved by applying modern optical electronical and space technology.
In order to develop some manufacturing technologies of industrial solar space electric power stations it is necessary to develop a demonstrative solar space electric power station on the basis of present space-rocket technics that allows first of all development testing of guidance of a high accuracy, keeping of laser ray on the ground photo-integrated area and developing of highly-efficient utilization system of radiation generators’ heat of energy transfer channel.
The development of such demonstrative solar space electric power station on the basis of present space-rocket and optical and electronic technics that has a level of transfered power equal to10-100кW is feasible today and all obtained technical solutions may be used for realization of the future industrial solar space electric power station and of net space system (nuclear electrical power unit-small-sized satellites).
Keywords: space solar power station, laser, nonlinear optics
Thermal engines, electric propulsion and power plants for flying vehicles
Toughening environmental requirements of ICAO (International Civil Aviation Organization) on emissions from aircraft engines, forcing the major powers to search for alternative sources of energy, in particular to expand the scope of biofuels.The use of renewable biofuels obtained from plants or fatty acids is very promising. At present, aviation accounts for about 2% of man-made emissions of CO2. When using biofuel, the emission of smoke, solid carbon, carbon monoxide, sulfur, and total carbon dioxide is decreased. Thus, the use of bio-kerosene obtained from jatropha, instead of the traditional kerosene in aircraft would reduce «carbon trace» almost by 80%.
Alternative fuels have physical properties that are slightly different from the traditional kerosene. This paper presents results of an experimental study of the influence of the physical properties of the liquid on the parameters of air-fuel spray device for the front module pneumatic type of the combustor gas turbine engine. To determine the characteristics of the spray and the study of the process of crushing and mixing alternative fuels with high viscosity developed a model biofuels based of kerosene TS-1. As a result of this work has received a number of dependencies characteristics average diameter, velocity and concentration of fuel droplets in the stream of the burner of kerosene and biofuel model. Summarizing the findings, it was found that when using viscous fuels should be used pneumatic atomization method for the specified operating parameters of combustor gas turbine engine. Despite the fact that it is not yet available in the Russian industrial-scale biofuel production, this area has a great future because of the large acreage and water surfaces in our country.
Keywords: front module, atomization, biofuels, pneumatic, jet atomization, atomizer, swirler, combustor
Dynamics, ballistics, movement control of flying vehicles
A method of forming modes of the controlled motion of the tether systems to solve practical problems in elliptical orbits
Orbital tether system (TS) is separately formed area of the promising technologies . However, the consideration of the function of space bundles in the elliptical orbits is not sufficiently covered by specialized literature. In the known works [2-12] the solution of practical problems with the use of the TS is discussed in the terms of functioning bundles in the circular orbits, while a number of problems can be solved only in the elliptical orbits. The solution of problems of the dynamics of functioning of the TS in the elliptical orbits is more complicated than for the circular and requires a special theoretical study. Scientific problem, the solution of which is devoted to the work, is in full qualitative analysis of the topological structures of the dynamic system of the controlled motion of the TS and the formation of suitable modes of their movement during the operation in the elliptical orbits.
An effective method of the formation of modes of the controlled motion of the tether systems to solve practical problems in the elliptical orbits is proposed. The method is based on the mathematical apparatus of the qualitative theory of dynamical systems and the theory of bifurcations [13, 14].
All types of quality structures of a dynamic system of the controlled motion of related objects are set, all bifurcations of the system under study and the bifurcation values of parameters that define the totality of characteristics of the controlled movement in elliptical orbits are identified. It gives you the opportunity to have a clear picture of the characterization of possible trajectories of the controlled motion under all values of the control parameters, under any initial conditions of motion and at any period of time.
As a result of the analysis of all types of the qualitative structures of the phase trajectories, a set of implemented modes of the controlled motion is defined and the regions of initial conditions where they are implemented are set. The modes should correspond to particular steady phase trajectories of the system and the set of orbito-resistant non-singular phase trajectories that fill the fixed region of the phase surface.
Keywords: tethered system, modes of relative motion, controlled motion
The goal of this work is to conduct a comparative analysis of the known and future spacecraft insertion profiles to the orbits of Mars and Jupiter artificial satellites’. Different modifications of combined profiles are researched which require conducting of propulsive maneuvers with an aerodynamic acceleration of a spacecraft in the atmosphere, as well as the profile consisting in the propulsive orbit formation. The main optimality criteria are the minimum of total energy consumption and the maximum of physically realizable spacecraft reentry corridors.
The task solution of spacecraft optimal control is fulfilled with the use of necessary optimality conditions of Pontryagin’s maximum principle. The areas of rational application of profiles are detected including preliminary aerodynamic braking of a spacecraft in the atmosphere, shared control by aerodynamic and propulsive forces in the atmosphere, multiple passage of upper atmosphere by a spacecraft.
It is shown that the use of a combined profile for orbit-shaping with atmospheric maneuvering is high efficient as the power consumption with its use is 3-3.5 times less in comparison with the propulsive profiles during the insertion into the Mars satellite orbits and 7-10 times less during the insertion into Jupiter satellites.
It is determined that during spacecraft reentry near the lower boundary of the corridor it is reasonable to perform the propulsive trajectory correction maneuver. It allows reducing of total required energy consumption by 1.5-2 times or expanding of physically realizable reentry corridor by 10-15 % in comparison with the profile without a correction impulse. The energy consumption can be more considerably reduced for the profile with a spacecraft’s multiple passage of upper atmosphere. However, with the use of the given profile, the time for satellite orbit-shaping considerably increases.
The obtained results are of practical importance and may be used for deep space missions. The general principles of the methodological approach are adjusted for the solution of other tasks of spacecraft optimal control.
Keywords: spacecraft, satellite orbits, optimal control, minimum of necessary energy consumption, maximum of reentry corridor width
Instrument making, metrology, information and measuring equipment and systems
Information and measuring and control systems
The range of problems solved by modern multi-functional aircrafts constantly expanding. These circumstances make it necessary to develop new on-board algorithms, particular using the methods of artificial intelligence. Design of current and promising methods require evaluation of their efficiency, which makes it necessary to use new modes in the process. One of the most important stages at the introduction of new onboard algorithms is simulation, in which the comparison of various algorithms and implementing their programs and assesses their effectiveness. In the article estimates based on modern methods of probability theory and mathematical statistics, as well as results of their use in the evaluation of the effectiveness in the simulation of the stand HIL.
Modern maneuverable aircraft must solve the problem of resource allocation and management task such as multi-criteria problem of recognition with it using artificial intelligence techniques. Solution of such problems by using a strictly mathematical description and on the basis of on-board resources is often impossible. These circumstances make it necessary to develop new on-board algorithms. The introduction of modern and advanced method requires the evolution of their performance, which makes it necessary to use new methods. Article focuses in the use of new approaches based on the methods of probability theory allow more objectively evaluate the effectiveness of the implementation of useful tasks.
Keywords: maneuverable aircraft, unmanned aerial vehicle, onboard algorithms, flight mission, confidence interval, efficiency
Radio engineering and communication
Radio engineering, including TV systems and devices
Space radiation impact on FPGA based digital units and irradiation stability hardening methods for such systems
Field Programmable Gate Arrays (FPGAs) are increasingly being used as a key component of digital systems due to their in-field reprogrammability, low non-recurring engineering costs, and relatively short design cycle. These characteristics, combined with high performance and high logic density, prove their feasibility for a number of ground and space level applications. Recently, a great interest aroused in using FPGAs onboard a spacecraft. FPGAs, like all semiconductor devices, are susceptible to radiation exposure. Radiation effects on electronic circuits used in extra-terrestrial applications and radiation prone environments need to be corrected. Since the variety of FPGA manufacturer’s offers, the radiation impact on them need to be studied and robust methods of fault tolerance need to be devised.
The main subject of study in this paper is the effects of cosmic ionizing radiation on FPGAs, and some fault-tolerant design strategies. The paper gives a classification of radiation effects and classification of the various methods of increasing radiation resistance of digital equipment. Operation principles of the presented method are also discussed in this paper. The main result of the work is analysis of the advantages and disadvantages of methods allowing increasing the radiation resistance of digital FPGA-based devices and recommendations for hardware developers on the use of these methods.
This paper summarizes the radiation effects on FPGAs, and methods to mitigate these effects. It also provides a case study of a successful FPGA system operating in space.
Keywords: ionizing radiation, field programmable gate array (FPGA), digital signal processing, radiation resistance
Antennas, SHF-devices and technologies
It has been shown recently; that metamaterials (multilayered metal-dielectric structures with unusual electromagnetic properties) can improve radiation characteristics of antenna, for example increase its gain without increasing antennas lateral size. In order to manufacture such multilayered metal-dielectric structures several techniques, based on thick and thin film technologies are used. If creating a microwave multilayered split ring resonator based metamaterial with distance between two layers over 1 mm is necessary, this techniques not always can be used. In this case dielectric layers and films with metal structures must be manufactured separately and then multilayered metamaterial modules must be assembled. In order to assemble these layered structure assembling and testing bench is used. During the assembling process a microwave radiation source with antisymmetric radiation pattern is used for matching each layer. Microwave radiation of the source is transmitted through matched layers and then received by reciever. Ideally matching is perfect if minimum of the signal power at the receiver is achieved. To confirm capability of the bench experimental research was carried out. Test two layered structure and special radio transparent fixture were made, one of the layers being fixed and the other one being movable. Signal power at the receiver dependency of the displacement between layers of the test two layered structure at frequency 27 GHz was measured. Experimetn shows that estimate matching error is approximately 100 mkm. The Designed assembling and testing bench provides technologically efficient assembling and testing metamaterial based multilayered antenna modules with distance between two layers about 1-10 mm and for frequencies range approximately 1-30 GHz and matching error less then 1,5 % of wavelength at operation frequency.
Keywords: metamaterial, antenna module, split ring resonator, radiation pattern
Systems, networks and telecommunication devices
The principles of realization of the mobile satellite communication network standard DVB-RCS with the spatial frequency resource time division in the X-band
Satellite networks handheld earth stations are ongoing through the spacecraft in geostationary orbit, as a rule, with direct relay with frequency-division multiplexing (FDMA).
Transition to the standard DVB-RCS. with a spatial frequency TDMA, involves placing on board a spacecraft multipath receiving-transmitting antenna and multi-board digital platforms standard DVB-RCS, providing multi-channel demodulation of earth stations. Using the DVB-RCS standard with MSF-TDMA can significantly extend the functional characteristics of mobile networks through satellites in geostationary orbit [2, 3, 4, 5].
To move to a higher rate of information transfer, adopted in satellite communication networks standard DVB-RCS, need to be more than an order of magnitude increase the energy potential of satellite radio links spacecraft , which can only be achieved through the establishment of on-board the spacecraft multipath receiving-transmitting antennas.
As a prototype under consideration DVB-RCS standard mobile satellite communication network creating issues with MSF-TDMA is used in the currently deployed in the X-band portable earth station network operating in the direct mode, the relay FDMA frequency division channels. Earth stations in the network, despite the relatively high functionality and power characteristics, to ensure a direct telephone connection to each other is forced to operate at the lowest possible data transmission speeds.
Modernization of communication satellites by the introduction of the multipath receiving-transmitting antennas allow to implement X-band-based earth stations, networks mobile satellite DVB-RCS (MSF-TDMA) standard, which will be provided by the possibility of organizing a high-speed direct connection of subscriber earth stations each other.
Proposed in the present work the modernization of communications satellites option by installing on-board the satellite multipath receiving-transmitting antenna implementing DVB-RCS standard with the space-time-frequency resource sharing, enables the creation of mobile satellite communication networks standard DVB-RCS through satellites in geostationary orbit.
For the practical implementation of these proposals in the paper version of the modernization of communications satellites greatest challenge is the creation of high-speed digital switches, a key element of the multipath receiving-transmitting antenna for satellites in geostationary orbit implementing zonal service.
Keywords: mobile satellite communication network, distributed resources, standard DVB-RCS, multipath receiving-transmitting antenna
For increase of efficiency of group of unmanned aerial vehicles (drones) [1, 2, 3] the adaptive radio network with switching of packages which knots are aircraft is used.
For providing requirements to an adaptive network it is necessary to solve a number of complex problems, in particular, to provide effective management of a strip of frequencies, to develop adaptive route protocols and to choose optimum route metrics [4, 5, 6].
Now the protocols of routing focused on search of the shortest route distance with a binding to network topology and location of hubs [5, 7, 8, 9, 10] are used.
Despite a great interest to the considered subject, in our opinion not enough attention is paid to questions of modeling of probabilistic and time characteristics of algorithms of routing. The offered work is devoted to research of efficiency of algorithms of routing in the conditions of not stationarity, in particular, at change of structure of a network.
In this work the adaptive radio network with switching of packages and casual access under the Aloha [11, 12, 13] protocol is investigated.
Influence on characteristics of algorithm of routing of qualitative characteristics and volume of route information which knots on the office channel, and also options of the organization of the office channel exchange is considered. It is shown that the problem of routing can be solved if to be limited to calculation of the metrics containing only data on a condition of knots (nodal metrics). The volume of information distributed by knots in this case is proportional to a square of quantity of knots. However in some cases it is necessary to transfer, along with a state as well data on characteristics of communication channels between knots (channel metrics). The volume of information distributed by knots in this case is proportional to a cube of quantity of knots that significantly exceeds information volume in case of transfer of nodal metrics. It is shown that generally transfer of channel metrics is actual for display of new network structure in local route matrixes of each knot at reorganization of a network.
The option of the organization of the office channel depends on the volume of the transferred route information. At the small volume, in particular, by transfer of nodal metrics, the allocated channel can be used, and mailing of route information is carried out along with an exchange of information packages. If the volume of data is big, in particular, by transfer of channel metrics, interruption of transfer of information packages for a while which is required for mailing of data on new structure of a network is necessary.
For the purpose of increase of efficiency of a network by transfer of channel metrics use of the combined mode at which transfer of metrics is carried out in information package in the mailing mode is offered. Results of imitating modeling have shown high efficiency of the combined method in the certain ranges of change of a traffic and power of the channel.
Keywords: unmanned aerial vehicles, adaptive networks of data transmission, casual access, routing, network matrixes of contiguity, routing metrics, imitating modeling
Radiolocation and radio navigation
Complexation of the airborne radioelectronic radar systems for the indirect identification of objects
Means of the radar system with active response are used nowadays to identify objects detected by side-looking airborne radars. Analysis of the experience of using a radar system with active response testifies its lack of effectiveness, especially in terms of multi-purpose complex and signal-jamming environment. A perspective approach to the development of the systems of identification of objects is formation of systems of indirect identification. Functioning of such systems is based on the use of information on the types (classes) of the observed objects and comparison of this information with a priori information on the types of objects used by the warring parties of the conflict. On Board of the aircraft the radar station and the station of electronic intelligence can be attributed to the sources of information on the types of the observable objects.
The aim of this work is the development and research into the algorithm of the indirect identification of objects using information from the airborne radar and the station of electronic intelligence. The problem statement of the development of the algorithm of the indirect identification of objects is made to achieve this goal. The type, state affiliation, class of object and index of its identity with the source of radio emission, observed by an electronic intelligence station are considered to be parameters describing the state of the identifiable object, observed by a radar station. Statistical relations between types and state affiliation, types and classes of objects are formalized by using the appropriate conditional probabilities. Dynamics of change of the parameters of the state of the identifiable object in a discrete-time is described using Markov and nominal-Markov chains. Also it is assumed that the airborne radar makes decisions on the type of the identified object, and the electronic intelligence station makes decisions on the class of the observed source of radio emission. The accuracy of the generated solutions is known and described by the corresponding probability matrixes. In addition, decisions on their identification are formed according to the coordinates of the observed objects that are measured by the stations. The accuracy of these decisions is described by the corresponding probability matrix. Rules of forming the decisions that are optimal in criterion of the maximum of the posteriori probability on the state affiliation and type of the identified object are derived with the use of the Bayesian approach.
Surveillance of the airborne radar and the electronic intelligence station, and also the information on the statistical relations and the dynamics of change of the state parameters are used in the calculation of the posterior probability of the state parameters of the identifiable object. The comparison of the algorithm with its simplified version is made in the interest of the study of the efficiency factor of the developed algorithm of the indirect identification. As a result it is concluded that the gain in the accuracy of the indirect identification of objects from the use of the algorithm may exceed 10% in terms of determining the state affiliation and exceed 30% in terms of determining their types.
Keywords: identification of objects, complex information processing, radar, electronic intelligence receiver
The purpose of this article is development of solution algorithm of optimization task of multiposition radar system space structure with uncooperative source of illumination given the limitations for mutual location of the MPRS elements and also limitations for quality of radar system information.
For the solution of the task, there was determined target function — cross section of the working zone of MP RS on the given height of the target flight. We chose the criterion of optimality — maximum of target function and stated the limitations. The area of analysis is presented in a form of discrete set for which maximum possible number of variants of MPRS space structure is determined. Then, using the brute force method we determine the value of target function for every structure variant satisfying the given limitations and choose a variant with which maximum target function is achieved. The choice of optimal variant of space structure allows us to fully realize potential possibilities of MPRS for the detection of objects and measure of their coordinates.
There was offered an algorithm of solution of optimization task and the results were obtained of the optimization of the space structure of the multiposition radar system with uncooperative source of illumination and three receiving stations. Efficiency of the use of algorithm is assessed by the value of coefficient of working zone increasing.
Keywords: multi-position radar system, uncooperative source of illumination, optimization of the space structure, brute force
Informatics, computation engineering and management
System analysis, control and data processing
On solution of the problem of correcting scalar terminal state of an aircraft for an arbitrary distribution of a multiplicative perturbation
We investigate the problem of correcting scalar terminal state of the aircraft. We consider the case of one correction. The correction is carried out by a high-thrust engine. The initial state of the aircraft is random. Distribution of the multiplicative perturbation connected with implementation error of rated specific impulse is arbitrary and independent fr om the initial state of the aircraft. Optimal control is selected in the class of piecewise constant functions, depending on the initial position of the aircraft. Optimal control is searched by maximizing the probability that the terminal state will be in a certain zone. We find an analytical expression for criterial function by the law of total probability and propose an algorithm of searching for optimal solution. Since we should optimize the function of unknown origin on open sets for searching for optimal solution, then we approximate criterial function by the method of middle rectangles. To find optimal solution of obtained function we discretize the initial probability measure and we replace the continuous random variable characterizing the multiplicative perturbation by the discrete random variable in approximating function. Then we reduce the optimization problem to the mixed-integer linear programming problem. We consider an example. We investigate the dependence of the optimal value of the criterion on the number of the segments of the partition and the number of realizations for a fixed set of input data for calculations using the IBM ILOG CPLEX package. We show that the accuracy of solution is more influenced by the number of segments of the partition, rather than the number of realizations, if the number of realizations is large. In the example we give a form of optimal control, which is close to control, obtained using the optimal confidence set in the case wh ere the initial position and the multiplicative perturbation are normally distributed random variables. The resulting control has a dead zone and is nonlinear.
The minimum-time problem of the linear discrete-time system with convex set of the feasible controls is considered in this paper, i.e. problem of transferred given system to 0 by means of feasible control in minimum number of steps. Specifity of 0-controllability problem for linear discrete-time systems is related to the difficulty of using conventional methods. These features is characterized by lack of explicit form of the solve of the problem of dynamic programming and lack of analogue of Belman’s equation, incorrectness of maximum principle for minimum time problem in discrete-time case, nonuniqueness of optimal solution.
The algorithm of the construction an optimal solution has been developed in previous works. But this method can be applied only to the systems with linear constraints of the feasible controls set. The main improvement of the new algorithm is its workability for any systems with the convex constraints on the controls. This fact is reached by using polyhedron approximation instead the real set of the feasible controls. The theorem of the convergence of the sequence of polyhedrons to the compact convex set, which is approximated, is formulated and proved in this paper.
Also the method of the estimating of the accuracy of approximation is represented in this paper. It is based on the calculating of Hausdorff distance between two polyhedrons. This problem is reduced to projecting exterior points of the first polyhedron to the faces of the second polyhedron, i.e. this is the quadratic programming problem with the linear constraints.
The designed algorithm is tested on the problem of the minimum time orientation of the aerostat. As a mathematical model, a solid body suspended on a cord and able to perform rotational movements is used. The upper end of the cord is fixedly mounted and operated with two fan motors, generating the opposite control moments about the vertical axis. The body is subjected to the torque is linearly dependent on the angle of rotation caused by an elastic cord and the moment of viscous friction linearly dependent on the angular velocity. It is assumed that the engines instantly gaining momentum, influence on the running engine center of gravity is neglected, and the atmosphere is considered to be stationary and homogeneous. This model is described by linear discrete-time system with convex set of the feasible controls.
Keywords: linear discrete-time system, minimum-time problem, polyhedron, Hausdorff distance