2016. № 91
Mechanics | |||
Deformable body mechanics | |||
New ICAO requirements for external aviation noise reduction draw increasing attention to the new types of airframe design/layout to use airframe as shield from engine noise. While targeting external noise reduction, the wingbody layout looks like the most promising. This layout places engines over the airframe. It is necessary to note that this layout leads to increase of the airframe area which suffers from acoustic loads. In turn, these loads produce the stresses which can lead to fatigue airframe failure. So despite of significant progress in aviation engine noise reduction, the discussions about acoustic fatigue and durability of aircraft structures (for example, plates and shells) gain back their popularity. In this paper we proposed the hybrid numerical-analytical method to calculate the response and durability of isotropic metal plate under broadband acoustic loads with four different acoustic field spatial distributions: fully correlated, partially correlated, delta-correlated and diffuse field distribution. For the simple-supported metal plate, mean square stresses and durability obtained by the proposed hybrid method were compared with the exact analytical solution. It is necessary to note, that proposed hybrid method may be applied for the plate with clamped-clamped or clamped-simple supported edges. The mean square stresses, calculated by the hybrid method, fit well the exact analytical solution but are highly sensitive to acoustical field spatial distribution, external acoustic field frequency spectrum and number of eigen modes taken into account. We calculated durability by using four different approaches providing the mean square stresses as input data. Calculations performed by Wirsching-Light method (for narrowband Gaussian process) and Kowalewski method (for wideband Gaussian process) give, correspondingly, lower and upper estimations of the plate durability. Miles and Rajcher methods (both are for wideband Gaussian process) produce relatively close values located between the results of Wirsching-Light and Kowalewski methods. Keywords: spatial correlation function, cross correlation function, isotropic plates, acoustic fatigue, acoustic endurance |
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Interaction of the linear viscoelasticity constitutive equation with several failure criteria is studied under uni-axial creep conditions in order to simulate creep rupture and to assess lifetime of viscoelastoplastic materials or structural elements. The limit strain criterion and two proposed new families of hereditary failure criteria are considered. They are constructed to take into account a whole creep curve and damage evolution. The proposed failure criteria families depend on a positive real parameter and include the limit strain criteria as a particular (limit) case. Every criterion of the first family yields rapture time that is greater than the one given by the limit strain criteria and every second family criterion yields rapture time that is less (or equal) than the lifetime given by the limit strain criteria. The difference between the predicted creep lives can be made negligibly small or considerably large. The failure criteria governing parameters regulate their memory fading rates and provide an additional option to tune the model and fit it to creep rapture test data. Equations of long-term strength curves generated by three chosen failure criteria are derived for arbitrary creep function. Their general qualitative properties and their dependences on the criteria governing parameter and creep function are studied analytically and compared to each other. It is proved that qualitative properties of all three theoretic long-term strength curves are the same as basic properties of typical test long-term strength curves of viscoelastoplastic materials. Thus, coupling the linear viscoelasticity constitutive equation with fracture criteria considered in the paper provides adequate qualitative description of creep rupture and lifetime of viscoelastoplastic materials and structural elements. Keywords: viscoelastоplasticity, creep, fracture criteria, mean creep rate, creep life, long-term strength curves |
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Fluid, gas and plasma mechanics | |||
The paper presents the results of numerical studies of ignition and detonation of boron dispersed particles with air combustible mixture. A simplified physico-mathematical model of the process was developed. The dispersed particles are considered two-component and consisting of boron and boron oxide. Material melting and evaporating processes are allowed for, as well as surface reaction or boron oxide formation. Carrying gas is multicomponent staying in thermodynamic equilibrium. The presence of boron fine particles, boron oxide and boron nitride in combustion product is allowed for herein. The structure and minimum velocity of stationary detonation wave propagation, as well as maximum velocity of the flow at stationary-state combustion were obtained by computational method. It was demonstrated that calculated wave parameters asymptotically approach their equilibrium values. Keywords: numerical simulation, metallized fuel, chemical reactions, phase transitions, combustion, detonation |
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Physical — chemical radiation plasma-dynamics promptly developing field of science finding application at the solution of problems of engine building of the space-rocket industry. In [1-9, 14-16] the special attention is paid to computer creation of optical models of gases and the plasmas intended for the solution of problems of radiation plasma-dynamics. Such constructions are based on quantum-mechanical calculations, these or those approximations and semiclassical generalizations of elementary radiation processes. In work [3] for mass calculations the so-called optical model of the environment was formulated. It is necessary to emphasize that in this treatment temperature of the environment and radiation is supposed the general, the Sakha and Boltsman local thermodynamic equilibrium (LTE) is used [6]. In our works [7-8, 14-16] kinetic approach was considered. Constants of different plasma chemical reactions are necessary for this purpose. For reaction of photo-ionization process , ( – concentration of excited state, – a photon energy, – ions concentration) consideration begins with the simplest model of hydrogen and record of matrix elements that is useful for the beginning reader. Calculations of photo-ionization cross sections for hydrogen atom are given. There are Kramers approach [12] for other more difficult atoms, with replacement of the main quantum number by effective quantum number , где , — the potential of atom’s ionization of is used. Values of effective quantum number are given for atom Xe.
The method of quantum defect is considered in details [7]. Results of calculation of photo-ionization cross sections for xenon (the maximum value in a threshold) are given in the table.
The maximum values of photo-ionization cross sections
Xe (in units 10^{- 18 }cm^{2}).
Results of calculation of photo-ionization cross sections for xenon are given on the figure. For the purpose of simplification in case of mass calculations some simplified treatment with use of a formula of Kramers is specified.
Keywords: Xe plasma, photo-ionization cross section, method of quantum defect |
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The work deals with numerical simulation using semi empirical turbulence models which include a differential equation for turbulent viscosity in two-dimensional case. k‑ε‑µ_{t} model [5] and k‑ε‑µ_{t}(Λ) model [6] are used to describe the mean turbulent parameters. The one-parameter models of eddy viscosity (ν_{t} −92 [7] and Spalart, Allmaras [8]) are used in one of the jet problems. Averaged flow and turbulence parameters are implemented in Cartesian and cylindrical coordinate systems. Simulation of axisymmetric subsonic jet in quiescent air in initial and transition regions with mean velocity u=87m/s have been conducted using k-ε-μ_{t} model. Initial region length has been determined with reasonable accuracy. Difference between calculated and experimental velocities is less than 5%. Verification of turbulence models in the flat plate boundary layer problem with M = 0.5 have been performed. Skin friction coefficient and velocity in logarithmic coordinates are compared with analytical solutions. Underexpanded supersonic turbulent jet simulation at M = 2 in the nozzle exit [13] have been conducted. Calculated static pressure and Mach number distributions along the jet axis are compared with experimental data. The k-ε-μ_{t} model reproduced 7 jet barrels. The positions of the maxima and minima are closest to the experiment in comparison with other models. The maxima and minima of the pressure oscillations and Mach in all barrels underestimated. The ν_{t}‑92 model reproduced 12 jet barrels that is fully consistent with the experiment. The positions of the maxima and minima are distinctly shifted in comparison with experiment. The k-ε-µ_{t}(Λ) model reproduced the flow similarly with k-ε-μ_{t} model (7 barrels), but predicted flow core length is bigger. Spalart, Allmaras model reproduced only 5 barrels and predicted flow core length is smallest in comparison with other models. Numerical simulation of supersonic axisymmetric jet from converging nozzle in quiescent air [15] has been performed. A comparison with the Pitot pressure and velocity distribution along the axis is shown. The ratio of the chamber total pressure to ambient static pressure equals to NPR=2.5 and 4. In the case of k-ε-µ_{t} model at NPR=2.5 the initial region length is in satisfactory agreement with experiment, but the number of oscillations is underestimated. The k-ε-µ_{t}(Λ) model overestimates the initial region length. Oscillations of the Pitot pressure and velocity have bigger magnitude for all jet barrels in comparison with k-ε-µ_{t} model. In the case of k-ε-μ_{t} model at NPR=4 the Pitot pressure in the first barrel is bigger than experimental value. The difference in amplitude decreases downstream. The peaks begin to keep up and become less appreciable. Pitot pressure produced by k‑ε‑μ_{t}(Λ) model is underestimated in the first barrel. The subsequent barrels predicted by the model are much better than the first. Numerical simulation of overexpanded cold jet using the k‑ε‑μ_{t} model in quiescent air at Mach 3.005 in the nozzle exit [16] has been performed. The calculated axis Pitot pressure is underestimated, but the position of the local maxima and minima and local minima values are determined with good accuracy. The biggest difference along the axis between the calculation and experiment is in the two initial jet barrels. The largest deviation from the experiment in all cross-sections is found near the axis. Keywords: three-equation turbulence model, supersonic axisymmetric under- and over-expanded jets, boundary layer |
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Aeronautical and Space-Rocket Engineering | |||
Design, construction and manufacturing of flying vehicles | |||
Manufacturing of new aircrafts requires development and improvement of new materials and technologies, ensuring ever-increasing demands for quality and operation reliability. Most carrying aircraft structures made of polymeric composites are machined to produce the high quality holes providing reliable fixation and assembly of composite structure (such as, spars of the main and tail helicopter rotors blades). Delamination that can reduce the material structural integrity is basic technological problem, occurring while fiber reinforced composite materials drilling. Tool’s geometry and machining conditions are the most important factors affecting the quality of the processed holes. The main purpose of this work consisted in the study the process of drilling holes in a multilayered polymeric composite of “GFRP-titanium” type, which is employed in the design of the Mi-28 helicopter rotor blades spar, as well as for soft tool predicting the quality of the holes development. Using a series of experimental data, including the delamination sizes depending on the machining conditions, the database for the further modeling has been created in a matrix form. Our first attempt to build an empirical description of delamination sizes, depending on two design variables (cutting speed and drilling feed) has been unsuccessful, probably, due to nonlinearity, generic for the drilling process. To overcome this difficulty we proposed and tested an approach, based on the artificial neural networks (ANN) implementation, to predict the quality of the holes drilled in the titanium foil reinforced glass fiber epoxy-based plastics. ANN training has been conducted using an errors back-propagation algorithm. Testing of the prediction accuracy revealed that ANN could provide the quality of size prediction exceeding 97%. According to the obtained results, we recommend to use the artificial neural network for the delamination at the GFRP drilling holes size prediction. In the process of statistics accumulation ANN are able to carry out self-learning and produce the results based on the newly obtained information, and, thus, adequately predict the quality of machined holes. Keywords: drilling glass fiber reinforced plastic (GFRP), delaminations, artificial neural networks, method of conjugate gradients |
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Strength and thermal conditions of flying vehicles | |||
For modern warplanes essential complication and expansion of a circle of solved problems is characteristic. At the same time conditions of their operation become complicated: flights are made in a broad band of altitudes and speeds, with various versions of loading on external, including, suspension points. The listed features demand profound studying and an estimation of the is intense-deformed condition (NDS) of configuration items of the plane as a whole and outer wings in particular. Researches of the NDS of the plane on the basis of the conventional approaches which appreciably are based on land and flight experiments, becomes more and more expensive, labour-consuming and long, and, in some cases, and impossible on safety conditions. The numerical methods using modelling of a design of the plane in the form of beam and balochno-lamellar schemes [1], have limitations at NDS calculation. Now the increasing role is played by the new approaches based on wide application of modern numerical methods and computer technologies [2,3]. In the known literature [4,5] at calculation of the NDS of a wing with aviation means of defeat (ASP) the interference between them is not considered. Nevertheless, between a wing of the plane and подкрыльевым ASP there is the significant interference interaction characterised by presence of horizontal, vertical and lateral interference forces [6,7,8]. Significant on value interference forces lead to occurrence in a wing additional bending and torques that essentially changes its NDS. Thus, working out and application of the techniques, allowing to consider influence of interference interaction between a wing and ASP on the wing NDS, is an actual problem. In the present activity results of an estimation of reliability of calculation in program ANSYS of parameters of the NDS of an outer wing of the plane are presented at supersonic speeds without aviation launching sites (APU) and with them, executed by comparison of experimental and computational values. Besides, results of research of influence of an interference on the outer wing NDS are presented at various rules ASP underneath the wing. Keywords: supersonic flight, the aerodynamic interference, the is intense-deformed condition, elastic wing, computational complex ANSYS, reliability |
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Thermal engines, electric propulsion and power plants for flying vehicles | |||
Many known projects of pulsejet realize the Humphrey cycle in their operation. Practically all the projects are aimed at argumentation of the pulse combustion chamber design. In the course of the pulsejet development, designers do not pay much attention to fuel-air mixture formation, though this process determines the combustion efficiency, and, as consequence, the amount of hazardous emissions, to which more and more strict requirements are placed. While fuel-air mixture formation, it is necessary to organize a volumetric circulation zone to spread it over the entire volume of the combustion chamber. The existing ways of circulation zones organization do not provide their large volume. When pulse combustion chamber design, it is necessary to control the flow in its air-gas channel to achieve the greatest possible volume of the circulation zone. We solve the scientific problem to ensure the mixing process in the pulse combustion chamber. The main purpose of this work is the process of pulse combustion organization of the fuel-air mixture. Scientific novelty of the work includes: — argumentation of pulse combustion chamber design; — technological process developing of fuel-air mixture organization in flowing combustion chamber with pulse fuel supply and its combustion; — development of methods for calculating parameters of the gaseous atmosphere in pulse fuel-air mixture combustion in the pulse combustor. Keywords: flow energizer, pulse combustion chamber, flame tube head, fuel-air mixture, circulation zone |
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Solving the problems of industrial purity (IP) of fluid systems and components (FSC) working cavities, and implementation of working and process liquids (WPL) of aircraft (AC) can significantly reduce consumption of liquidsю It also increases reliability and service life of onboard equipment (as a consequence, improves the flights safety); reduces the aircraft maintenance and servicing time (as a consequence, increases the aircraft combat readiness); reduces the complexity of maintenance. The object of research in this entry are the methods and means of ensuring aircraft FSC working cavities IP. The purpose of research consists in developing technological solutions and advanced hardware designs for effective treatment and control of contamination level of oil, fuel, hydraulic systems and components. Research subject refers to the priority areas of science, technology and engineering in the Russian Federation: NoNo 5, 7, 8, 9, and to basic critical technologies in the Russian Federation: NoNo 1, 24, 27 (Presidential Decree of 07.07.2011, No 899). During scientific research the authors carried out the following: analysis of the existing and prospective methods and means of cleaning-out and its quality control. They defined the trends for cleaning-up efficiency enhancement and its control validity. Cleaning-up technology consisting in FSCs’ internal cavities bleeding (with pressure and velocity fluctuations) was defined as a basic one. The obtained in the presented study significant positive effect on quality and duration of the cleaning-up process is achieved due to the fact that unlike existing technologies, the developed hydro-pulse technology realizes the non-steady fluid flow mode by periodic change of flow rate from zero to the value, effective for specific cleaning system without creating fluid pressure fluctuations (patent RF 1568343). Compared to domestic and foreign counterparts, this technology allows 2 to 3 class (according to GOST 17216-2001) quality improvement and 5 to 7 times cleaning process duration reduction, up to 10 times liquid systems and assemblies plunger resource increase. FSC IP level control is one of the most important manufacturing operations. It defines aircraft tolerance for use according to the drive parameters on one hand, and the aircraft manufacture, repair and maintenance on the other hand. It defines the moment of the FSA cleaning operation process termination, which occupies a significant portion of the total of the works on their service duration. For complicated spatial geometrical parameters of aircraft FSA internal cavities relevant Regulations foresee execution of their pollution indirect control ‒ measuring the contaminants concentration in the outflowing fluid from the controlled FSA during bleeding in the rinse mode and operation mode. In these circumstances, special attention should be paid to liquid sample drawing process. To improve the reliability of the liquid sampling the authors developed and and proposed methodologies and design solutions of sampling devices (SD) along the lines of: – full flow SDs, ensuring isokinetic sampling, as maximally identical to the object of analytical control, from which it was sel ected for use in ground bench (test, developmental, washing) equipment; – needle type SDs constructively with minimal weight and size fit to normalized elements of aircraft FSA reinforcement pipe systems, for their accommodation directly at the aircraft onboard systems, in coordination with the aircraft developers. The presented technological and design solutions are cross-industry and cross-samples value and apply to all objects of weapons, military and special equipment, containing in its design, fluid (oil, power, hydraulic, fuel, etc.) systems and units. The equipment developed in cource of the presented work is implemented in the OJ-SS “NIIASPK” serial products manufacturing (aviation industry), technical Adoption Deed of 21.04.2016, the results of the research on the technologies development implemented in Academy research effort and aviation industry, including those carried out by the State contract fr om 09.01.2014, No 14411.17B9999.18.001 for PAO "NPK"Irkut", the Adoption Deed of 17.03.2016, 01.06.2016 r .; in the educational process of the Academy, Adoption Deed of 01.06.2016 (the Implementation and Realization Acts are included). Keywords: industrial purity, liquid systems and components working cavities, workers and process liquids, aircraft, maintenance, sampling devices |
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This article is devoted to problems of development and experimental studies of micro-jet engines (micro gas turbine engine with a thrust of up to 1000N). The main focus is a test bench for engines of this class. During the project are solving the following tasks:
Presently, the authors are carrying out researches of designed micro-jet engines with thrust 100N and 400N using created test bench. The test bench works on the research of regime parameters of engines, as well as working out the design of the engine. Test bench consist of a mechanical part, movable rails for fixing the engine, test bench control system and measurement system. Test bench control system allows providing power to other systems: fuel pump, valves, measurement system, as well as start and ignition systems. Regulation is carried out by single parameter — fuel consumption. The measurement system includes: speed sensor, temperature sensor, fuel consumption sensor and thrust sensor. Test control and data collection are automated and are conducted by LabView environment. Engine is mounted on rails for ease of moving and assembly / disassembly, as well as allowing of its moving in the axial direction during thrust. Also, during 400N engine experimental research, defined it starting diagram, recorded correlation between fuel consumption and thrust. A test launch of 400N engine allows verifying it numerical model. Based on this verifies, for engines up to 1000N calculation software, is under developing. Keywords: Micro-jet engine, centrifugal compressor, test bench |
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Dynamics, ballistics, movement control of flying vehicles | |||
The subject of research and development consists in signal generation on a mnemonic indicator algorithm development for a seaborne aircraft. Research methods include system analysis, synthesis of structures and algorithms, simulation. The work aimed at a signal generation on the mnemonic indicator technique determination. The model included atmospheric turbulence, the mnemonic indicator, dynamic airplane control structure, and aircraft dynamics. The simulation models consisted of multiple systems of differential equations. The system was linearized for simulation. The signal generation on mnemonic indicator technique is offered for a seaborne aircraft manual thrust control mode during landing approach. Its basis is formed by complexation of signals, indicating flight speed deflection, angle of attack deflection and normal acceleration component, with no delay in a control loop. It allows correct dynamic characteristics of angle of attack thrust control loop, make them similar to flight speed deviation control, and simplifying by this the pilot’s task of aircraft holding in an permissible zone of the angle of attack variation in conditions of wind disturbances. Angle of attack control loop modeling for manual thrust control mode in the conditions of wind action were carried out. The Dryden gust model and a Monte Carlo simulation approach were used. Recommendations on a signal generation at the input of the mnemonic indicator algorithm parameters are given. Keywords: thrust control, angle of attack, mnemonic indicator, seaborne aircraft |
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Innovation technologies in aerospace activities | |||
The calculation of the guaranteed monthly average of solar radiation on the territory of Myanmar. The influence of the angle of inclination of the receiver of solar radiation to the solar radiation and the sel ected optimum tilt angle of the receiver. For some objects, distant from power grids over long distances, perhaps only Autonomous power supply, as connecting them to the centralized system requires a large capital outlay associated with the construction and operation of long transmission lines. For such objects the cost of electricity generated from renewable sources of energy becomes commensurate with the cost of electricity generated fr om power systems, and this factor ceases to be limiting for the application of renewable energy sources. In addition, Autonomous fuel-fired power plants have a lower quality of electricity, and when energy generators based on renewable energy sources gain great prospects to compete. The current values of solar radiation intensity and duration of their action depends on latitude, climatic zone, time of day and year, and other factors. Because of this they are random, so the probability of its intensity corresponds to the probability that the random variable in the interval: To increase the solar radiation by orientation angle of the receiving site. It is therefore necessary to calculate the optimal angle of the receiver solar radiation with the aim of maximizing the solar radiation during the year as a whole, and for monthly optimization of this angle. Comparing the arrival of solar radiation at different angles of the receiver of solar radiation in the cities of Myanmar we can conclude that the arrival of solar radiation during the installation of the receiver the solar radiation at an angle β_{сез}is reduced in all regions of Myanmar approximately 1 % in comparison with the arrival of solar radiation during the installation of the receiver the solar radiation at an angle β_{мес}. Therefore, the best option is the orientation of the receiver of solar radiation with the seasons twice a year, which allows no additional cost to the complexity of the solar system installation to a significant increase in the arrival of solar energy. Keywords: renewable energy, solar radiation, photovoltaic plant |
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Instrument making, metrology, information and measuring equipment and systems | |||
Navigation instruments | |||
This article deals with questions of strapdown graviinertial complex (BGK) efficient version design, redundant structure of its primary information sensors and advanced functional operation algorithm, making it possible to achieve sufficient accuracy of vector gravimetric measurements and determine the orientation and navigation parameters. The purpose is achieved through the use of functionally redundant blocks of inertial sensors, as well as through evaluation and correction of errors of inertial and satellite components of complex navigation system directly in the gravimetric survey. Functional algorithm is based on the basic equation of the inertial navigation with the use of optimal Kalman filtering methods in the case of a tightly coupled structure of a complex navigation system. The technique of functionally redundant blocks inertial sensors data treatment is presented. The listed mathematical expression are showing that an increase in the number of block units increases strapdown graviinertial complex accelerometers accuracy. A method of selecting a rational design of the accelerometers block with cone structure is describe. It is indicated that, in general, the best half-angle of the cone depends on the ratio of measurer statistical error model coefficients and the value of the measured vector. Calculations of inertial measurement unit with cone structures optimal configurations have shown that increasing the level of inertial measurement unit redundancy increases considered technical solution efficiency. For example, compared with the three sensors inertial measurement unit, in the case of four sensors influence the random error can be reduced by 14%, for the five sensors — 23%, six — 29%. Keywords: strapdown graviinertial complex, functionally redundant block, optimal estimation, vector gravimetric measurements, functional algorithm |
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Onboard equipment of middle range (MR) grade (UAV) must include an advance navigation complex, forming navigation data for control system. This data must meet high accuracy, availability, integrity and continuity requirements to provide safe flight and successful flight mission execution. In addition, hardware of MR UAV navigation complex must meet high weight and size, power consumption and final cost requirements. Meeting mentioned requirements causes use of low-cost and small-size systems and sensors of primary information, which in its turn causes the necessity of use primary data processing mathematical techniques, allowing to achieve defined performance. Required accuracy provision at different stages of flight for this UAV grade simultaneously increasing control automation today is not completely solved task. Landing is one of the most complex stages of flight and capability of automated landing depends heavily on the accuracy of navigation parameters determining. The majority of existing systems providing automatic UAV landing proposes use of global navigation satellite system (GNSS) integrated with inertial navigation system (INS). However, it is well known, that GNSS signals cannot be always available including jamming cases. Therefore, it is advisable to explore possibilities of INS integration with other systems, which are free of GNSS disadvantages to analyze the potential accuracy of navigation parameters determining. Based on photogrammetry artificial landmark image processing attitude and navigation system (photogrammetry system — PS) is sel ected as such system in this article, which has a high degree of autonomy and of insensitivity to interference as compared with GNSS. Due to the principle of its action PS is commonly used at landing stage and for its operation uses the photographic image fr om the onboard camera, which is usually a part of UAV onboard equipment. An option of scheme design and algorithms of INS and PS integration for use at UAV landing stage is offered. Required for synthesis of integration algorithms mathematical errors models of INS and PS are considered. Keywords: unmanned aerial vehicle, inertial navigation system, photogrammetry, complex information processing, landing system |
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Information and measuring and control systems | |||
The problem of non-measurable flight parameters identification, including wind affects and remained fuel weight, appeared necessary information for safety and flight control monitoring. The authors offer a multi-stage procedure of assessment, according to which less precise, but simpler means are implemented at the initial stages of assessment, while more complicated elements are put into operation as may be necessary. A complexed two-stage identifier of side wind is formed, consisting of a windblast estimation block, a block of its steady state value evaluation and a block of logic switching from one estimation to the other, using aperiodic filtering for the first case and modified Kalman filter for the other. The identifier, employing optimal Kalman filter prognosis operation, provides the most precise indirect estimation technique of the steady-state wind. The authors offered “freezing” the most significant for evaluation correcting matrix coefficients of optimal Kalman’s filter, and zero the rest coefficients, so as to eliminate variable coefficients and provide offload the onboard computer. According to the offered multi-stage identification concept, every stage employs different set of sensors. Satellite navigation data appears more useful for the situation of initial wind effect, as well as a group onboard sensors, such as accelerometers and airspeed sensor, reacting faster to wind changes than other sensors. To evaluate the steady-state value, other sensors, controlling the aircraft reaction, mainly, to the constant wind component effect. Keywords: multi-stage identification, signals complexing, flight parameters, wind disturbances evaluation |
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The object of article is the method of formation astatic control systems of dynamic objects with uncertain parameters on the basis of robust modal-invariant systems. The methods of formation static control systems for dynamic objects with uncertain parameters on the basis of the theory of modal-invariant systems are well known. The established value of controlled coordinate in the presence of parametrical errors and action of constant disturbances of object in such systems is a variable. There is a problem of formation of astatic system on the basis of a modal-invariant subsystem with integrating property. Thus there is no necessity for traditional addition of an integral link. It allows not to increase an order of system and represents practical interest especially at a hand control. Integrating properties of system are reached at the expense of maintenance of a zero root in the characteristic equation of a subsystem by known methods of modal control. After closing of system by feedback on the controlled coordinate we create astatic system. The offered method of formation of linear astatic system with preliminary formation of structure and parameters of a modal-invariant subsystem with integrating property provide astatism on control and disturbing influences, and also the lowered sensitivity to uncertainty of parameters of control object. The example of synthesis of astatic system is given and the possibility of reduction of its sensitivity to uncertainty of object parameters is shown. Keywords: astatic control, modal-invariant systems |
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Radio engineering and communication | |||
Radio engineering, including TV systems and devices | |||
The paper envisages the possibility of a low-pass filter sensitivity without its phase response deterioration. At present, high-speed radio data transfer lines operating in perspective frequency bands (such as K-band), digital means for radio signal filtration, meeting the Radio Regulations requirement do not exist. In this case, additional analog filter is added to radio transmission path. This causes intersymbol interference (violating Nyquist condition). Intersymbol distortions occur herein, caused by non-linear character of phase responses of the applied LPFs. Thus, the necessity of data transfer speed increase of radio channel data transfer (and, correspondingly, the effectiveness of radio frequency spectrum implementation) determines the necessity of carrier shaping by the filter with maximum amplitude-frequency response slope. The selectivity of the filters with group delay approximation is inferior to filters with amplitude response approximation. It to employing additional low-pass filters, deteriorating the group delay uniformity in the passband. One can conclude that the filter calculation implies compromise between frequency response slope outside the passband and the group delay uniformity in the passband. This problem can be solved by combining LPF with linear frequency response (such as Bessel, Gauss or Papulis filters) and notch sections with transfer function zeros outside the LPF passband to obtain the frequency response with greater slope without significant effect on phase response and, correspondingly, group delay. Implementation of notch elements with the rejection frequency selection irrespective of LPF cutoff frequency seems to be the most perspective technique. On an example of implementing the fifth-order Bessel filter for filtering out spectral components of impulse signals, the authors prove that the proposed technique allows ensure gain in suppressing minor lobes of pulse signal, while preserving the group delay uniformity. Keywords: filter selectivity, linear phase response, low-pass filter, band-stop filter |
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The paper considers the antennae arrays testing set carried out at the anechoic chamber (AEC). Automated measuring and computing complex (AMCC) was used for high-frequency feeders of centimeter and millimeter band slotted waveguide antenna arrays (SWAA), mm-band preamplifier parameters, estimating of mm-band airborne radar radome parameters, transparent radome influence at the mm-band SWAA performance measurement. Comparisson of the basic measured parameters with same antenna array measurements at the far field test range is presented. To define SWAA gain the absolute reflection from a mirror technique was applied. Its idea consists in comparing reflection coefficients from the fider matched measured space radiating antennae arry (AR) input, and from the input of the same antennae with a reflecting surface, installed at some distance of R in front of it. It may be either flat screen, or reflector. The matching disruption is explained by the antennae input impedance change affected by the flat screen, which is equivalent to the effect of the same antennae, but located at the distance of 2R and operating with opposite oscillation phase. The gain measurement error value caused by chamber walls reflections, and nonideal antennae input and fider matching, while oprating in free radiation mode, were defined by statistical averaging of measurement results obtained for various distances to the reflector. Experimental studies of absolute antenna gain measurement absolute reflection from a mirror technique demonstrated measurement accuracy of about of 0.5 dB match with far field relative technique measurements. These studies proved the possibility of narrow beam antenna array measurement at the near field. In the course of the studies another antennae parameters measurement technique was mastered, and a series of experiments was carried out. Anechoic chambers impllementation allows signifficantly reduce or even completely eliminate the far field test range tests. It leads to significant cost and time savings associated with complex electronic equipment development. Keywords: Anechoic chamber, near field scanner, antenna radiation pattern, antenna gain |
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Radiolocation and radio navigation | |||
The article is devoted to the problem of the detection and coordinate measurement of small unmanned aerial vehicles (UAVs) in the city with strong reflections from the local objects. This problem is related to the rapid growth in the number of UAVs and with a relatively soft laws aimed at the regulating and organizing of small UAVs flights. Therefore, it is necessary to provide the safety of the important objects and places with mass of people from possible threats associated with the use of small UAVs and to monitor the air space at any time and in any weather conditions. Only radar sensor meets these requirements. It’s noted that there were attempts to solve this problem with using military radars that designed to detect mortar and artillery shells. But these radars are very expensive. Therefore, truly effective solution to this problem is the producing of a cheap short-range radar system for detection and tracking of such UAVs. However, using the radar for these objects that fly at low altitude, is associated with the complexity of the detection process. This is due to the presence of spurious background reflections from objects of urban area. These reflections exceed echo-signal from UAV by orders of magnitude. The methods for detection of small-sized aerial objects against the background of intense reflections from the underlying surface (US) were noted. The detection can be implemented by extending the spectrum of the probing signal (PS) with reducing the pulse duration. This PS does not have side lobes of range selection function (SF) that allows to observe small target in close proximity to major. Using an ultra-short pulse (USP) PS allows to apply inter-periodic compensation methods, that allow to solve problems related with the small radial component of the velocity vector of the UAV. The results of the radar field tests in terms of urban development are presented. It was able to detect hovering and low speed UAVs during the experiment. Echo signals of several production samples of UAVs were investigated. The algorithm of calculation and the obtained values of average radar cross-section (RCS) for the UAVs are presented. The images of radar indicator with source data for different durations of the PS, including the UAV marks, are noted in the article. The authors note that measured average values of RCS using USP radar are large enough for stable radar detection UAV at 3-5 km range. Keywords: UAVs detection, short-range radar, ultra-short pulse radar, moving target detection |
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The article describes the problem of creating a location system based on mobile units, adding new functionality without changing the communication systems’ hardware component count. Target detection by equipment employed for communication systems equipped with vertical pin vibrators is limited not only by the parameters of the antenna radiation pattern, but also by the level of the amplifier maximum output power level, usually not exceeding 5 W. The Defense Advanced Research Projects Agency (DARPA) started the realization of a similar air-based project for deploying on unmanned aerial vehicles this year. The proposed decision is aimed at the modernization of the existing mobile subscriber communications with antenna suspension height not exceeding 2 m. To ensure the energy stealthiness of wireless devices operating in radar mode and determining the local coordinates of targets the proposed method consists in using simplex codes with a large base. The carried out computations revealed, that implementation of codes with 4096 base as an expansive pseudo-random sequence, can ensure energy stealthiness at the level of —20 dB with a probability of target detection no less than 0.9, and the probability of false detection of about 10^{-6}. It is possible to build Kasami family for the selected base. The authors carried out computation of target detection parameters, and defined the target distance error, which amounted to about 5 m, with a detection distance of about 5 km and an effective scattering area of a target of about 6 m^{2}. The proposed method is expected to be tested on radio communication mobile devices, with an output power up to 5 W, and omnidirectional antennas. For the obtained data analysis, an earlier proposed modified Fortune algorithm will be used, when the curve is used sweeping right line for Voronoi diagrams plotting. Such an approach will allow reduce the target errors in range up to 2.5 m and azimuth up to 10^{–3} rad correspondingly. Thus, the number of communications devices involved in the location should be greater than three, including no less than two radiation sources, operating alternately. Keywords: communication systems, radar, energy stealthiness, target detection, correlation functions |
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Informatics, computation engineering and management | |||
System analysis, control and data processing | |||
We consider the problem of determining the optimal assignment of aircrafts for carrying out search and rescue operations (SRO) based on the assumption that only one aircraft is allowed in the zone during the SRO. Every zone, attainable fr om given aerodromes should be taken into account [1]. The goal is to maximize the total search time by all involved aircrafts. In order to ensure compliance of both conditions, we proposed to solve the problem in two stages. The goal of the first stage is to maximize the number of aircrafts that can be assigned to the SRO zones assuming the latter are reachable fr om the given aerodromes. The goal for the second stage is to maximize the total search time. We can assign the task of finding the maximum possible aircrafts, which can be distributed to the SRO zones in the form of matchings “type of aircraft / aerodrome” (TA), as follows:
subject to:
where m – the number of SRO zones; k – the number of different TAs; h_{i} – the amount of aircrafts of i^{th} TA; x_{ij} – variable, that adopt values either 1 or 0, depending on whether the aircraft of i^{th} TA is assigned to j^{th} zone SRO or not. We represent the assignment of the second task in the following way:
subject to:
where t_{ij} – search time of the i^{th} TA in j^{th} zone SRO (taking into account flight time to the zone SRO since departure and flight time to return to the aerodrome); — the goal value (1). We proposed to consider two methods of solving assigned tasks: • Simplex method; • Methods based on algorithms for solving Boolean satisfiability problems (SAT). It is necessary to emphasize that assigned tasks belong to the class of pseudo boolean (PB) linear programming problems (LPP). In most cases, algorithms, based on the simplex method, are applied to solve the problems of this class, as a result of the inapplicability of itself. However, due to the structure of assigned tasks, it is possible to use simplex-method without any modifications to obtain the optimum PB solution. In recent decades, the determinants of Boolean satisfiability (SAT Solvers), based on the SAT methods, have made significant progress. The record performance of modern SAT Solvers opens up new prospects for their use in applications wh ere previously it was considered to be possible only conditionally. However, due to the NP-completeness of the SAT-problem, there are examples, the time, required to search for the optimum solution of which, is showing the exponential growth. One of SAT approach inapplicability cases is demonstrated later in terms of assigned tasks by the example of the currently best SAT Solver in PB LPP category [2]: Nagoya Pseudo-Boolean Solver (NaPS) v. 1.02b [3]. During the analysis of the assigned tasks, the algorithm, that under certain conditions, related with input data, can reduce the dimension of the assigned tasks, was developed. It is given below: Suppose k TA and m SRO zones are given. Furthermore, we can distinguish SRO zones, attainable only by i^{th} TA.
Then the algorithm becomes as follows:
Testing the effectiveness of the developed algorithm was carried out with solutions sensing method (SSM) [4]. SSM — is the method for solving PB LPP, which has exponential complexity. Consequently, it is particularly sensitive to reduction of the assigned tasks dimension. This became the reason of selecting this method. We will use the abbreviation of MSSM for SSM modification with the developed algorithm.
Figure 1 — Comparison of SSM and MSSM effectiveness growth Based on the results (fig. 1), the following conclusions can be made:
Examples, which evaluated the effectiveness of the selected approaches, can be divided into 2 groups:
This separation is explained by the following formula:
demonstrating the increase rate of the solution space, depending on the input data.
Figure 2 — Illustration of the Naps 1.02b results for the 1^{st} group of constraints
Figure 3 — Illustration of the Naps 1.02b results for the 2^{nd} group of constraints Time spent to find the optimal solution of the same test examples using the simplex method in all cases did not exceed 3 ms. According to the results of the tests (fig. 2, fig. 3), the following conclusions can be made:
Based on these results it is the simplex method we proposed to use for solving such class of problems. Keywords: search and rescue operations, linear programming problem with boolean variables, unimodular matrices |
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Computing and control systems elements and units | |||
This paper presents adjusted mathematical model of angular velocity transducer (AVT) based on optical tunnelling effect (OTE). The effect of the initial gap, the optical source incidence angle and optical spot radius on the of the angular velocity transducer based OTE characteristics is calculated at different angular velocities. The article studied the effect of the ring resonator primary and the second mode of angular velocity transducer based on optical tunnelling effect (OTE). The initial mathematical model assumed parallel displacement of the gap between the prism and ring resonator. It determined optical output power on photo detector by the optical spot central point. In real configuration, the ring resonator surface is deviated a few nanometres from the prism surface. Considering the gap variation for different contact points of the optical spot, it is possible to determine the adjusted mathematical the primary mode model. In the secondary mode, the adjusted mathematical model is defined based on the gap change at various points of the ring resonator surface. The OTE-based angular velocity transducer is implemented using the results of the initial and adjusted mathematical models. Optical output power is defined according to the compensated mathematical model by various contact points on the prism border. This paper presents the study of the OTE-based angular velocity transducer, and proposes the adjusted mathematical model for the ring resonator first and second modes. The authors considered the effect of the output power errors when using the adjusted mathematical model compared to the initial model with variation of the initial gap, radiation source’s incidence angle, and the optical spot radius. The paper demonstrates that the optical spot radius affects strongly, and for relative error, no more than 1%, the optical spot radius should not exceed 50 mcm. Incidence angle herewith affects the output signal, and it can be changed within the range from 42° to 50°. The results of the article allow study error elimination while AVT design. Keywords: transducer, angular velocity, optical tunnelling effect, ring resonator, mathematical model |
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Automation of technological processes and production control | |||
A force majeure resulting in the necessity for temporary reactor trip may occur at the nuclear power plant (NPP) while normal operating mode. The paper envisages one of the operation c aspects of nuclear power plant operation in force majeure conditions. The station is assumed to consist of several power units being at various stages of the campaign. Let there is a necessity to NPP trip due to a force majeure. The threat termination can occur at an arbitrary point of time either. It is quite clear that not all power units in general will be able to raise the power up to nominal value immediately. This difference can be stipulated by, for instance, the presence of different operating reactivity margin for xenon poisoning compensation, or, in general, by different maneuver effectiveness. The authors consider the system, consisting of two reactors. With brief shifts between reloads after unscheduled trips of both reactors, a period exists when neither can restore nominal power, since both stay in iodine well. For the rest of time both reactors can restore nominal power in no time. On the contrary, with large time shifts one of the reactors at a certain point would possess reactivity margin to compensate the iodine well, when the other still stays in the iodine well. If the reactor stays at such a campaign stage, that it is impossible or undesirable to handle the control rods, to get out of the iodine well one should alter boric acid concentration in the active zone. Reactivity margin due to boric acid presence in the coolant is proportional to its concentration. Let the boric acid concentration time dependence within single campaign be approximated with enough accuracy by linear function. Since the moment of trip is random, we can speak about average flow time for starting one reactor at the power level depending on the shift. The paper offers setting and solution of the optimization problem for selecting the best time shift between the off-load refueling of nuclear reactors, allowing quick start of at least one unit after the reactor trip. This work demonstrates that the time shift between off-load refueling allows quick launch of one reactor, but does not allow the start of both. In the general, for NPP consisting of N reactors the optimum shift is 1/N of the reactor campaign. Keywords: nuclear power plant, nuclear reactor VVER, force majeure, optimization problem, iodine pit, compensation xenon poisoning |
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Computing machinery, complexes and computer networks | |||
Integrated computer system (ICS) operation in real conditions is associated with occurrence of various module failures, caused by destabilizing effects. The separate module failure herewith may lead to either system crash, or functioning in degraded performance mode, possible at the expense of reallocation of damaged module functions between the system good modules. One of possible system responses to failure consists in functional reconfiguration, while the system feature to keep the ability to fulfill its specified functions with required quality in conditions of functional failures is interpreted as functional stability. ICS reconfiguration task in flight requires permanent monitoring of the system condition, and decision making on optimal ICS configuration according to a known rule. System reconfiguration capacity defines directly its functioning safety and the task performance quality as a whole. Redundant resources available in the system define the above said abilities while of failure occurrence. Thus, the task of optimal (rational) ICS structural synthesis at the stage of design with restrictions on employed resources seems to be topical. The paper envisages algorithm of optimal distribution of aircraft ICS at the design stage, ensuring maximum level of functional system stability during failures under operation. For this purpose, the system structure is represented in the form of marked oriented weighed multigraph, which peaks match the system modules, while its arcs match the functions, executed by the given units. Such functions are defined as internal. The external functions call, or the system tasks, are determined as some assemblage of possible paths in the column for each external function. ICS structure representation in the form of the weighed digraph allows examine various versions of ICS structure in the condition of degradation, that is, a certain unit inability to execute specified function. Degradation leads to removal the ribs matching the given function from the column. Thus, the approach, which allows examine in-process the effect of units’ failures on operability of the remaining intact is offered. It means that the capability of functional links registration between the units, specific to hardware systems is employed. Resources redistribution within the limits of the offered algorithm is examined in two ways. Firstly, it is oriented on reaching external functions calls maximum execution quality at a runtime environment of everything not below the specified level. Secondly, it assumes redistribution of hardware-software means corresponding to a maximum execution quality of critical external functions calls. Selection of optimal ICS structure within the limits of the accepted strategy of resources redistribution is determined by optimization. In-process two criteria are offered (a survivability index, a figure of merit), which applicability is determined by singularities of particular ICS. The paper presents the results of numerical simulation. The offered algorithm can be used at the ICS design stage to meet the requirements on fail safety and survivability. Keywords: flying vehicle integrated computer system, functional stability, functional failure, degradation, multigraph |
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Mathematica modeling, numerical technique and program complexes | |||
The paper is devoted to development of new statistical data processing technologies obtained during simulation of missile motion in accordance with the complete mathematical model for a big quantity of randomly realized sets of tolerances, each of them is characterized by a specific transient process. The necessity for the research has emerged in connection with the fact that existing diagnostic methods did not allow identify variants of tolerance combinations, whereby the oscillations with frequencies, amplitudes and durations exceeding the design values, occur in the respective transient processes. The process of critical variants manual study is labor intensive and ineffective. Not only is the information on the spectral content, but also the spectral components temporal localization is of interest herewith. Thus, the classic Fourier processing, with only frequency representation of a signaldoes not allow solve this problem. A new methodology is described, allowing automation of the frequency and time domain analysis process of a large quantity of nonstationary signals. This methodology is based on the implementation of wavelet and wavelet package transformations of one-dimensional signals to obtain their frequency and time presentations, and subsequent analysis with pre-set parameters. The paper presents an example of the developed methodology implementation to reveal the variants of tolerances combination, located on the stability boundary, where oscillations’ with frequency, amplitude and duration higher than the preset values present in the respective transient processes. The main results of the developed technique implementation for stabilization algorithm parameters adjustment are presented. Keywords: statistical modeling, data processing, motion modeling, transient, time-frequency analysis, wavelet analysis, Daubechies wavelets, stabilization algorithm |