2016. № 88
Dynamics, strength of machines, instruments and equipment
Prediction of limit states of pipelines of high pressure of hydraulic and gas systems in the commissioning phase
In the manufacture and operation of pipelines of various diameter high-pressure hydro-gas systems in the air and rocket, there is the problem of forecasting safe their life. Statistical methods of calculation of durability of the effects of cyclic loading allow large scatter in the data and suggest the use of unnecessarily large reserves of strength. Therefore there is a need for research and development of criteria that take into account the mechanical properties of materials under complex stress state and defect structure of the material of construction. This is possible by using acoustic emission techniques.
Normally, before entering the hydro-gas systems in their operation under pressure 25% higher than the maximum operating this load causes an elastic-plastic deformation of the material of construction of the first cycle of loading and acoustic emission. If the capture test parameters of the acoustic emission, it is possible to establish a microstructure of the structural defects of the material.
To develop and test the proposed methodology in Komsomolsk-on-Amur complex program material longevity research has been developed State Technical University with software loading on different trajectories of mechanical low-cycle loading in flat tension conditions.
Cyclic loading of tubular samples in the chosen path was made before its destruction n and simultaneously recorded acoustic emission signals. acoustic emission signals in the analysis were divided according to the degree of danger of generating sources. Each recorded acoustic emission signal is seen as a time series, formed a kind of dynamic system, and fr om the standpoint of nonlinear dynamics of the task is to determine the dynamic system of degrees of freedom for the one-dimensional projection of its evolution in the phase space.
Using modern methods of nonlinear dynamics for the one-dimensional time series was reconstructed multidimensional attractor, the metric properties which are very similar to the evolution of the study of the dynamical system.
Knowing the general laws of change of the acoustic emission signal parameters for certain values of stresses for the structural material, it is possible to build a surface lim it Status Word for reference points for the respective kinds of stress-strain state, for all values of voltage and determine the durability of parts experiencing cyclic loads along any path loading. With the above approach, this will require setting a minimum number of time-consuming experiments.
Thus, the prediction of longevity of details of pipelines of hydro-gas systems in aircraft and rocket may carry out the initial stages of operation for the acoustic emission signal parameters with a high degree of reliability at a relatively small number of preliminary experiments.
Keywords: durability, structural materials, cyclic loading, the trajectory of loading
Aeronautical and Space-Rocket Engineering
Aerodynamics and heat-exchange processes in flying vehicles
Maneuverable aircraft lateral stability ensuring at high attack angles by differential deflection of the wing leading edge flaps
The purpose of the work consists in studying the possibility of ensuring lateral stability of maneuverable aircraft at high attack angles by wing leading edge sections differential deflection with via computational experiment using detached-eddy computational experiment.
The authors used numerical experiment and analysis as methods of working.
Leading edge flaps are used on modern aircraft to provide smooth flow around wing leading edge without separation while attack angle increasing. We propose to deflect only the root sections of leading edge flaps at high values of attack angles. It will allow fixing separation over the leading edges end sections and balancing aircraft loose-flow vortex structure.
The paper carries out comparison of lateral aerodynamic performances of a maneuvering aircraft obtained by detached-eddy computational method. It presents the range of aircraft attack angles where implementation of the suggested wing leading edge sections differential structure is efficient to improve its aerodynamic performance.
The calculations were performed using the method of detached eddy simulation. Pressure fields in aircraft sections and its surface were used to analyze the flow-around structure.
The results of this work can be used by scientific and design organizations engaged in development of maneuverable aircraft aerodynamic configurations and control systems, as well as by aviation universities for educational process improvement.It is expedient to use the suggested leading edge flaps differential configuration with attack angle values of 28–33 degrees, which will allow static transverse stability degree increase, as well as yaw angles values at which it preserves transverse and lateral stability. With this, the wing leading edge flaps differential deflection within this range leads to slight reduction of the aircraft lateral static stability reduction.
Keywords: maneuverable aircraft, aircraft lateral aerodynamic performance, wing leading edge flaps differential deflection
While aerodynamic design many authors used the inverse problem to improve the profile aerodynamic performance. However, applications based on solving the inverse problem are not widely used for helicopter airfoils for the reason that their aerodynamic design requires simultaneous monitoring of several regimes of plow. For this reason, the general inverse problem with additional constraints on the airfoil pitching moment was formulated at the previous stage of the study. The purpose of the present study was to clarify the applicability of this mathematical model for successive improvements of helicopter airfoils integral aerodynamic criteria.
Based on the generalized inverse problem solving method, the author developed the pressure distribution adjustment procedure for successive improvements of helicopter airfoil performances.
The paper describes the application of the generalized inverse problem concept for aerodynamic design of helicopter airfoils. It considers the following pressure distribution improving variations for NASA series airfoil:
Airfoil pitching moment increase at zero lifting force and small Mach numbers without noticeable losses of maximum lifting force values at small Mach numbers and maximum lift to drag ratio at moderate Mach numbers.
Airfoil maximum lifting force increase at small Mach numbers and practical permanence of the other integral criteria.
Airfoil lift to drag ratio maximum increase moderate Mach numbers and practical permanence of the other integral criteria.
The interactive decrease of wave drag at high Mach number and practical permanence of the other integral criteria.
The results were verified by CFD calculations.
This study established that mathematical model based on the concept of generalized inverse problem and simple physical considerations allow modify pressure distributions successively improving helicopter airfoils performances.
Keywords: airfoil design, helicopter airfoils, inverse problem
The assessment of the impact of the wind vortex structures arising from the flow of the mountainous relief on the plane approaching the landing
Aircraft landing is one of the most difficult flight stages in the conditions of mountain relief. The most frequently happening accidents are caused by human factor. Therefore, additional attention is required to the training of pilots flying in the mountainous terrain. First of all, it is about training pilots on flight simulators. The main advantage of using the flight simulator as the training is the safety of the emergency situations working off, which is extremely dangerous in a real flight.
For flight simulators the simulation of the air currents in the mountainous area of an airfield is an important point in the formation of the aircraft landing conditions on the mountain airfield.
In this article the method to determine the most dangerous conditions of the landing approach of the aircraft in the mountainous terrain was described, as the assessment of the impact of the wind vortex structures arising from the flow of the mountainous terrain. The estimation was made on the basis of the data obtained in the course of calculation of the parameters of the wind vortex structures for the Kushok Bakula Rimpochee Airport.
The article aims to create a scientific and technological advance in the field of developing the technical equipment for flight personnel training, as well as in the modernization of existing ones. The results, which are given in the article, can be used to improve the level of the pilots training by doing aircraft landing in the conditions of the mountainous airfield. The importance of this problem is due to the need to improve the safety of the aircraft landing.
Keywords: the safety of flight, mountainous airfield, vortex structures, aircraft landing
The article addresses a method of digital processing for gas flow photos. It gives numerical analysis using the criterion of image intensity at all gas flow stages (before compression shock, in the compression shock and beyond it). Laws of variation of image intensity values are seen to be correlated and depend on the streamlined body shape and initial flow rate.
Quantitative parameters of image intensity which characterize the gas flow in compression shocks and wave flow areas were identified using linear regression analysis.
In case of “horizontal” gas wave flow, the arithmetic mean deviation of intensity was selected as a determining parameter. In case of several compression shocks, the arithmetic mean of the difference between the maximum and minimum intensity values in the compression shock was selected as a criterion. For the “inclined” gas wave flow, the arithmetic mean deviation of intensity relative to the regression line was selected as a determining parameter. The mathematical apparatus for calculation of suggested criteria is offered.
Keywords: supersonic gas dynamic flow, experimental studies, image intensity, visualization methods, shadow photograph digital processing, shock-wave process, correlation coefficient
Strength and thermal conditions of flying vehicles
The work is devoted to the first stage of solving linear decoupled quasi-static problem of thermoelasticity for a circular cylindrical shell of variable thickness — the study of the temperature field during the heat pulse of radiant heat flux fr om an infinitely distant source of radiation. The thickness of the shell changes smoothly along the taper near the ends. Between design and the environment comes convective heat transfer by Newton’s law.
Plane-parallel pulsed heat flux falling on the shell perpendicular to its axis of rotation. The ambient temperature in the considered time interval and temperature of the shell at the initial time equal to zero.
The solution of the problem carried out in two stages: first, the temperature field of design during pulse heating , and then after the cessation of the heat pulse.
It is believed that the conditions are met
wh ere and - the coefficients of the temperature- and thermal conductivity of shell material, respectively, - is its thickness, – is the coefficient of heat transfer from the structure to the environment. This allows you to take the assumption of a uniform heating of the shell during pulsed heating and subsequent cooling.
The process of heat conduction by the district to coordinate both stages of the solution of the problem can be neglected when
( R — the shell radius, - the pulse duration ).
The case when the shell thickness decreases with the distance from the end face according to the exponential law. Using Laplace transform the problem of determining the temperature field after instantaneous pulse heating. The calculations showed that when
valid neglect of the process of heat conduction along the axial coordinate. The proposed asymptotic dependence for calculation of temperature fields during pulse heating and subsequent cooling of the shell. These techniques ensure sufficient for practical calculations, the accuracy in the analysis of thermal processes in the elements of thin-walled aircraft structures.
Keywords: shell of variable thickness, temperature field, convective heat transfer, radiant heat flux, the Laplace transform, asymptotic solutions, aircraft
This work presents the carried out analysis of catalytic active surface impact on heat transfer intensity while the body of axisymmetric shape is flown around by dissociated airflow. One has to tackle problems of such kind in the course of aircraft duration flight with supersonic speed in the atmosphere. The main feature of heat transfer on the surface of flying vehicles of such type consists in heat- and mass exchange between the surface of the lying vehicle and chemically active layer along the whole flight trajectory. The heat transfer intensity in this boundary layer depends entirely either on gas state parameters or chemical state of high-temperature air components mixture. Overall, these two features, in the end, determine the boundary layer type: equilibrium, non-equilibrium, «frozen». The above said is an important issue, since the boundary layer type determines the selection of the certain class of heat-protective material.
The studies of heat transfer in non-equilibrium flow of dissociated gas  conducted by various authors revealed that with flying vehicle flight at the altitudes above 40 km, high-temperature air parameters are such, that the molecules passing through the shock wave and compressed layer dissociate into atoms. The atomic gas in its turn enters the boundary layer zone, diffuses to the flying vehicle surface and recombines on it. As a result of this physico-chemical processes complex, heat currents into GLA structure drastically increase. The heat exchange intensity in this case strongly depends on catalytic activity of thermal protection materials.
American researcher R. Gulard analyzed for the first time the problem of catalytic activity of materials on heat transfer in dissociated currents. However, while deriving the equation for heat current density R. Gulard was incorrect while setting up the problem. This work modifies thereupon Gulard’s equation, and obtains new equation. The authors compared the calculated and experimental data on heat currents densities into catalytic active surface. The calculations were made both using Gulard’s equation and the newly obtained equation. The paper shows the mismatch of the calculation data obtained according to Gulard’s equation, experimental data and the results obtained using the newly obtained equation.
Keywords: reactive boundary layer, surface catalytic activity, heat and mass transfer, thermal protection, hypersonic aircraft, mathematical model, processes of thermo-gas dynamics and heat-mass transfer
Thermal engines, electric propulsion and power plants for flying vehicles
The objects of research are heat-stressed parts of high-temperature gas turbine engines (GTD) and gas turbine plants (GTP) with the complex system of branched channels.
The purpose of research is the development of the methodology for thermal designing of cooled structures of high-temperature gas turbines of 5-6th generation GTE and GTP on the basis of the experimental database.
The creation of blade modifications differing in the cooling channels design by the conventional technique of the investment casting is connected with great difficulties and is time-consuming technological process. Therefore the expeditious conduction of the research of a number of versions of the modified blades is so difficult. The developed methodology will allow to solve the complex problem aimed at increasing the reliability and service life of modern gas turbine engines while minimizing experimental studies and, consequently, material costs and power inputs.
For the achievement of this aim in the paper the manufacturing techniques of the modifications of the cooled gas turbine blades such as modular development, implantation technology, development of a ceramic rod were considered and analyzed.
For the creation of a basic original project of the blade at the early stage of its designing when there is not the executed in metal version, the choice of types of heat exchange intensifiers, of their arrangement and geometrical parameters is carried out proceeding from the analysis of empirical and experimental data. The subsequent development of the original project of the basic blade on the thermal state is carried out on the simplified on geometry and material versions executed with the use of universal equipment. The modular development technology allows to adjust the design of sel ected area in the blade on the thermal state, but there are difficulties with observance of the uniqueness conditions and the boundary conditions at interface of the areas of an internal cavity.
For the purpose of the adjustment of the blade on the thermal state at the later stages of its designing when there is the casting version of the basic blade, the technology of the development with expeditious changing in the design of cooling channels by implantation method is developed. This technology allows to carry out changes in geometry of the internal cavity on the prototype and to receive directly a qualitative assessment of the thermal state obtained as a result of the carried-out changes.
For the final development of the gas turbine blade on the thermal state and for its adjustment on the workability in the course of a mass production, the technology of the development of the ceramic rod forming the cooling channels in the blade modifications is used. This technology of the development of the design of the ceramic rod allows to carry out expeditiously the constructive changes in the internal cavity of the blade, however requires the accurate equipment and highly qualified specialists.
Scientific novelty of researches consists in the development of the comprehensive program of thermal designing and improvement of the constructions of heat-stressed parts of GTD and GTP with the purpose to increase the reliability and service life of the engine based on the high-informative methods of research and control of their functional parameters.
The practical significance of the offered methodology of the thermal designing consists in decreasing laboriousness and reducing the material costs for experimental adjustment of designs of the cooled gas turbine blades, and also in increasing the accuracy of qualitative assessment of their thermal state. The proposed complex of scientific and technological decisions allows to shift the focus of the experimental work fr om full-scale tests to simulation studies, and thereby to reduce significantly the material costs for the development of the GTD as a whole.
The received samples of the constructive elements of the aircraft equipment can be used in the development and creation of modern and perspective gas turbine engines, and also in the creation of thermo-technical devices.
Keywords: high-temperature gas turbine, cooled blade, thermal-hydraulic characteristics, liquid-metal thermostat
The pulse combustion chamber is involve: flame tube head, designed in the form of a check valve; parallel portion volume for mixing fuel with air and combustion; gas collector for flow throttling; pulse fuel nozzle for fuel feeding; spark plug, igniting the fuel-air mixture; peripheral flow swirler. Creating a volume circulation zone is one of essential points in pulse combustion chamber design because it has a great effect on burning in the pulse combustion chamber of a gas turbine engine. Availability of circulation zones in a pulse combustion chamber determines air-fuel mixing efficiency, which in its turn influences the value of propulsive burn and release of NOX, CO and other pollutants. That is why it is very important to know the structure of the flow in the combustion chamber. It is effected by many factors but only some of them considerably change the size of circulation zones. They are DКС combustion chamber diameter, DС diameter of outlet section of the combustion chamber gas collector. One effective way of flow structure controlling is using of the flow swirlers in the pulse combustion chamber Control actions of the circulation zone size are geometrical characteristics of the swirler which include swirler blade angle, swirler blade height, swirler blade pitch, swirler blade chord length, swirler blade camber. Researches have been implemented in the experimental unit known as «gidrobasseyn» by varying of above-listed factors. As a result of the hydrodynamical research were identified the best geometrical adjectives of the flow swirler, blade angle of the flow swirler , blade height , height of the blade chord, blade pitch of the flow swirler which equal to 10 blades. The combustion chamber diameter will be define by lean on diameter of a gas turbine engine midsection and diameter of the pulse combustion chamber adjutage . Aggregate result of the researches is significantly increase of the circulation zones. Experimental research of the above-mentioned factors determines the best geometrical characteristics of the pulse combustion chamber, optimal control action on the circulation zone size and the whole research resulted in considerable increase of circulation zones.
Keywords: swirler, pulse combustion chamber, flame tube head, recirculation mixing zone
Dynamics, ballistics, movement control of flying vehicles
The goal of the paper consists in developing an algorithm of changing an orbit inclination with low thrust electrojets. The spacecraft with eight electrojets with reaction wheels takes up a high elliptic orbit. Electrojets are necessary to control either the center of mass, or angular motion.
The system of four reaction wheels with total kinetic moment of 30 N m s realizes around of center of mass control. Several constraints are imposed on correction as follows: the change of an orbit period should be minimal; only one electrojet at a time can be in use due to energy saving restrictions; correction run time should not exceed one hour with possible allowed deviation of one minute.
Algorithm with three engine firings was developed based on equations for orbit period stability and equations for spacecraft angular movement. Equations for period deviation estimation during correction were obtained from Kepler law using eccentric anomaly. Angular momentum variation law equations include spacecraft and reaction wheels angular moments, as well as electro jet moment. The authors used the diagonal spacecraft inertia tensor.
Analytical equations for spacecraft angular momentum with reaction wheels calculation with an allowance for electrojets are obtained.
The paper presents the comparison between existing orbit correction algorithm with four firings and the developed algorithm. Numerical simulation results show that the algorithm involving three engine firings can be implemented with some restrictions for the initial angular momentum.
Keywords: orbit correction, orbit period, high elliptic orbit, electrojet engines, reaction wheels, angular momentum
The conditions of existence of limit cycles in dynamic motion system of related objects on an elliptical orbit
Orbital tether system (TS) is separately formed area of the promising technologies. Research work should be combined with experimental design work and provide science-based data (the results of theoretical research of problems of dynamics of flight control laws-deployment-folding design-exploratory research elements of TS) to establish programs for flight and special devices able to complete the target task .
The solution of problems of dynamics of functioning of the TS in elliptical orbits is more complicated than for circular and requires a special theoretical study. The conducted scientific studies of the problems of dynamics of the relative motion of the connected objects [2-8] showed the effectiveness of applying the mathematical apparatus of the qualitative theory of dynamical systems and bifurcation theory [9-11]. The full results of qualitative research provide an opportunity to develop a clear picture of the possible types of phase trajectories of the system, and, consequently, 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.
When conducting qualitative research of dynamic systems of the controlled motion, the most difficult is the determination of the bifurcations associated with the appearance and disappearance of limit cycles, covering the phase cylinder. In this regard, in this paper we formulated and proved two theorems.
It is analyzed the dynamic system of controlled motion of related objects in the plane of the elliptical orbit without taking into consideration disturbing factors. On the basis of the mathematical apparatus of the qualitative theory of dynamical systems defined by the equilibrium state, conditions for the existence of limit cycles are formulated and proved. The bifurcation values of the control parameter, associated with the appearance and disappearance of limit cycles at the considered dynamical system are determined.
The study of equilibrium states and conditions of the existence of limit cycles of a dynamical system has allowed to establish the number of all types of the qualitative structures of the phase trajectories of the controlled motion of related objects.
The range of values of the relative angular velocity of the continuum limit, covering the phase cylinder, is set.
Keywords: tethered system, equilibrium states, limit cycles
Instrument making, metrology, information and measuring equipment and systems
Considered the possibility of creating vertical sensor on the basis of physical or mathematical pendulum which has increased resistance to perturbing horizontal acceleration of object. A positive result is achieved by forming a corrective signal on the pendulum fr om the accelerometers, angular motion sensors and feedbacks.
As a result of theoretical analysis and simulation show that the rational choice of the corrective elements parameters can be realized quasi-imperturbable pendulum vertical as a backup, and in some cases the main vertical sensor to a certain class of aircrafts.
The physical and mathematical pendulum, disturbing by base accelerations, adjusted by a high-frequency accelerometer and some other correction sources. Depending on the relative position of the original pendulum and accelerometer formed corresponding control algorithms that significantly affect the dynamics of the vertical sensor and the steady deviation from the vertical angle. For example, for the horizontal acceleration ax steady deviation angle from the vertical is: (1 — δ) ax / g, wh ere δ — feedback depth 0 <δ <1. That is, under certain conditions, such a pendulum becomes quasi- imperturbable and can find useful solutions.
This study proves the possibility of creation of such vertical sensor for different objects, conditions of use and functionality.
In particular, as a backup artificial horizon, primarily for the UAV, as a device for the correction of SINS on objects for different purposes, or as an independent in the formation of the INS horizontal channel, when used with one or two-component tracking housing.
As element base of vertical sensor standard components can be used: pendulums, accelerometers, CRS as macro and micro performance depending on the required accuracy, weight, size and power constraints.
Of interest is the ability to create vertical sensor on this basis in the form of a one-piece structure made of the same type on the design and technology of correcting elements, for example, carried out with the use of quartz glass as the main material of construction of the main functional elements required.
Keywords: quasi-imperturbable pendulum, accelerometer, rate gyro, correction, pendulum vertical sensor, feedback
Attitude solution for fixed-wing aircrafts using a magnetometer remains relevant due to its well-known advantages. Taking this fact into account inertial-magnetometric method is proposed for computing roll, pitch and magnetic heading angles in static position of an aircraft as well as in motion, but with some restrictions depending on included sensors and algorithmic support.
There exists a well-known problem of ambiguity of spatial attitude defining in case of measuring geomagnetic field by a single three-axis magnetometer. In proposed inertial-magnetometric device the problem is solved by applying two magnetometers set horizontally and rotated 180 degrees about vertical body axis. Complementing the system by block of triaxial gyroscope allows to connect multiple measurements of geomagnetic field in time, filter measurement errors and increase the accuracy of attitude computation.
The research was conducted for three cases: case of fully eliminated deviation of magnetometers and absence of angular misalignment error between them, case of angular misalignment error of 0.5 degrees and 1 degree with the flight above magnetic anomaly. The research justified the application of two magnetometers for solving aircraft attitude defining problem. The research also resulted that estimated attitude angles maintain acceptable accuracy at increase of angular misalignment error between two magnetometers. Along with this the influence of magnetic anomaly almost doesn’t reduce the accuracy of estimation.
Thus, three angles are defined. Along with this the estimation of angles is provided without accumulation of error and with following accuracy: pitch and roll of about 0.2 degrees rms, magnetic heading of about 0.6 degrees rms.
The device is fully autonomous and allows usage of microelectromechanical gyroscopes with drift of about 300 degrees per second, and has an ability of self-recovery and readiness time of 10 seconds.
Keywords: autonomous device, inertial-magnetometric, magnetometer, geomagnetic field, attitude computation algorithm
A Suboptimal Estimation and Parameters Identification Algorithm for Aircraft or Other Vehicle Navigation Systems Using the Earth's Magnetic Field Information
The purpose of this paper is to present the solutions of the problem of nonlinear filtering algorithms synthesis and analysis for magnetic field navigation systems (NS) of an aircraft or the like for military and civil applications.
A three axis orientation magnetometer mounted on an aircraft or the like is used for sensing the earth’s magnetic field and for forming the nonlinear measurement vector with the measurement noise vector taking into account the declination maps.
The solutions of the problem of algorithms synthesis and analysis for magnetic field information signal processing were obtained by using the suboptimal extended Kalman filter (EKF) which allows to estimate the magnetic course of an aircraft, the inclination angle ( the angle a vector representing the total magnetic field makes with its trace on a horizontal plane), the module of the magnetic-field strength vector and the Poisson’s coefficients, indicating the constant and the inductive magnetization.
Computer simulation results of the adaptive filtering schemes reflect the behavior of the state vector estimates, the estimates errors, the covariance matrix, and the a posteriori hypothesis probability density with comparison for different conditions with different initial values and different Gaussian white noises vectors of the system state and of the measurements with corresponding variances, for imitation of environmental influences on the system.
The estimated magnetic course can serve as necessary information for the true course computing on board of NS, in the radar silence and radio silence modes, during a flight above surface areas with uninformative relief such as deserts and oceans, and as a method of accumulating errors correction for inertial navigation systems.
The proposed algorithms and system of course determination provide high efficiency and estimation accuracy comparing with other existing navigation algorithms and permit to abandon the performing of laborious and expensive magnetic deviation work inherent for traditional algorithms.
Many scientific researches have been performed in the class of adaptive filtering scheme of the state vector estimation together with parameter identification. The purpose of this paper is to propose new approach of the extension of EFK adaptive estimation in the classical stochastic dynamic systems with deterministic structure to the case of signal processing and parameter identification in stochastic magnetic NS using the theory of Markov processes and optimization of stochastic systems with random structure or with switching parameters.
Keywords: extended Kalman filter, identification, navigation system, magnetic fields, Markov processes, optimization of stochastic systems with random structure
Acoustic devices and systems
Application of informational approach to the solution of a problem of a defectoscopy by a method of free oscillations
On the example of free oscillation method, the author considered the methodology of information approach to the solution of a fault detection problem with a great number of unidentified factors. The paper presents either general conceptual, or particular functional diagrams in addition to free oscillation method, which point the place and interaction of such analysis methods as induction and deduction while opening the «black box» of a defect. These functional diagrams contain several heuristic stages of reference synthesis. The first stage features primary uncertainty elimination of solution region with respect to the presence of fundamentals within the frequency range, determined by the quality of manufactured samples, complemented by the subsequent statistical measurements, which identify the boundaries this range. Ultimately, linking the second part of the solution with the results obtained at the third stage, allow determine the uniqueness of the solution obtained, i. e. the fact of the presence of additional harmonics means the presence of the defect. As a result, the bandpass filter thus obtained, will present that significant reference, and further fault detecting equipment algorithm will be developed in relation to this reference. The formed reference herewith will be compatible with complex hardware path of contact excitation and wireless acoustic signal receiving. Such an approach to reference forming allows drastically decrease the number of calibration measurements, since the method of specified products testing is set. The paper presents positive results obtained with arbitrary signal model and practical examples of implementing the given methodology, which does not make use of complex physical calculations of complex phenomena while elastic interaction peculiar to implementation of free oscillations method. Typical defect search results on casting pump body of a complex shape located in the area of the threaded portion of large diameter and a massive disk weighing 90 kg with thickness of 70 mm with thin cracks and delamination up to 70 mcm are presented as illustrations.
Keywords: spectrum, free oscillations method, standard, acoustic waves, induction and deduction, information approach, methodology
Radio engineering and communication
Radiolocation and radio navigation
It is well-known that the Earth’s lower and upper atmosphere conditions have a significant impact on radio wave propagation. Refraction and time delay are the most important effects in relation to the Ultra High Frequency radar. The improving of the target tracking accuracy requires the accounting of atmospheric effects on the radar operation mode.
The effectiveness of the compensation medium effects on a radar operation is presented in the paper. We have developed a model for calculating atmospheric effects on the radar for its use in near real-time. This model is primarily focused on correcting the effects that are responsible for radar range and elevation angle bias error. Two ways for corrections calculation are considered. The first way is using climatological models for long-term forecast. The second way is based on the real-time updating method of the ionospheric model using slant TEC measurements for short-term forecast.
The two-dimensional ray tracing scheme is applied to calculate corrections. The corrections are provided for the radar in the form of three dimensional look-up tables with 10 min intervals. The each target measurement (range, elevation angle and azimuth) can be corrected for each radar hit.
We have performed a comparison between radar measurement and reference data of the calibration satellite position to make this evaluation. The results of comparison between real radar measurements and reference measurements showed the high efficiency of applying the operational corrections forecast.
The range error decreased by 47.6% and the elevation angle decreased by 65.4% for the long-term forecast. As for operational forecast, only the range error decreased by 82% and the elevation angle remained unchanged.
Keywords: radar, ionosphere, ionosphere model, updating of ionosphere model, atmospheric error, total electron content
Informatics, computation engineering and management
Automation of technological processes and production control
Automated process control necessarily implies the formation of five components: the objective and constraints (resources) of a process, alternatives and the selection criteria in the performance of the process and a model of the process. The paper proposes a structural and logical approach to the synthesis, verification, monitoring and control of process models. Each step of the process is represented as a universal network structure, built on the principles of Petri nets. This versatile network structure of the operation is the distinctive feature of structural and logical approach. Simulation capabilities approach, taking into account the modifications introduced Petri nets sufficiently match the complexity of logical relationships of various technological processes. The network structure is graphically represented in the notations of Petri nets, and formalized by means of set-theoretic approach.
To enable optimal process control shows the version of the mathematical structure of the selection of the optimal control on a simulated process. The structure comprises a set-theoretic model of the controlled process, a variety of options tuples layouts input position universal network structures that act as control actions, a set of relations that limit choice and reflecting the technological, technical, territorial, resource, space-time requirements, as well as a set of relations of preference ( performance), determine the choice of the optimal tuple. Marking the universal structure of the operation is the output position information on the current status of the operation.
As an example of solving the optimization problem management process represented a universal network structure, the features of the application of the method of dynamic programming-ing. In accordance with generally accepted procedures using the method of dynamic programming in the elements, and the notation of the proposed model of the process considered the construction of a multi-step management process with the production on it optimal control problem. Then analyzes the elementary approach to the problem of having excessive computational complexity. Formulated and proved the principle of optimality of Bellman. Formalizes the reverse and direct the procedure for calculating the optimum process control.
The scope of application of the developed structural and logical approach and created its model-based information technology support system may be the process of decision-making in complex technical systems. The ability to solve optimization problems using the proposed model can greatly increase the effectiveness of such systems.
Keywords: model of the process, Petri nets, mathematical structure selection, the dynamic programming method
Article is devoted to increasing the efficiency of the spacecraft onboard software development, mainly debugging and verification. The analysis of existing in MEDB “MARS” onboard software development process was conducted in order to identify the stage where the introduction of information technology will reduce development time and increase quality. It was decided that the automation of the maximum number of steps is the main way to improve the existing process. It was concluded that creation of an information system to automate the development process — Test automation system (TAS) necessary. The system requirements were established. Based on this requirements and terms of implementation, it was concluded that the use of third-party COST systems for several typical problems solving is advisable. Integration of turnkey typical solutions and of custom own developed kernel system will greatly reduce time of system development and implementation. To simplify further improvements it was decided to use only open source third-party components.
Based on the identified typical tasks to automate, two standard-class systems for integration in TAS was marked out software version control system and software error management system.
Comparison of existing version control systems is given, on the basis of which Subversion system was chosen as the most simple. Similarly, a comparison of software error management systems, such as Redmine, Bugzilla, Trac is given. It concluded that Redmine has the best options set from these errors control systems.
The interaction interface between TAS with version control system Subversion and error management system Redmine is developed. The mechanisms of software systems integration into a common automation system were described.
The proposed solution has been successfully introduced into the production process and used in the development of several spacecraft control systems, including KazSat-2, Electro-L, Elektro-L № 2, Spektr-R.
Keywords: spacecraft onboard software development, development support system, project management, spacecraft onboard software test, Subversion, Git, Redmine, Bugzilla, Trac
Mathematica modeling, numerical technique and program complexes
Numerical method for solving nonlinear boundary value problem for differential equations with retarded argument
Considered the numerical solution of nonlinear boundary value problems for differential equations with delay by the false position method. Affecting the question of finding false position method’s parameter with more accurate methods of finding a number of possible parameter values and find the parameter in the case of solutions of a singularly perturbed equation. For more accurate location solutions and for finding all possible solutions used E. Lanaye’s parameter continuation method and the method of continuation with respect to the best parameter. The numerical studies demonstrate the advantage of using the described approach. In the case of solving a system of singularly perturbed equations using the false position method and the method of optimal parametrization it is possible to find all the solutions with the required accuracy, while other methods are not always possible to find all the solutions. Cauchy problem on each step of the the false position method solved by Runge-Kutta method of fourth order of accuracy. The suggested method of solution differential equation with retarded argument can be useful for solving tasks of mechanics of deformable solids, radiolocation, theory of automatic control.
Keywords: differential equations with retarded argument, numerical Methods, false position method, method of continuation with respect to the best parameter, E. Lanaye’s parameter continuation method
The decision support system for justification of selection of design parameters for stand-alone energy systems
One of the significant problems for the consumers, who has made the decision to pass to the stand-alone energy systems based on alternative energy sources is the choice of components meeting his requirements and effective in the climatic conditions of operation of the system.
The research objective is development of the layout of decision support system (DSS) to justify the selection of design parameters for stand-alone energy systems based on renewable energy sources — wind and Sun. Such systems are particularly often used by consumers located in remote areas where there is no possibility of using traditional energy network.
Simulation modeling of functioning of stand-alone energy system as nonlinear dynamic system, including main devices which are its part (solar panel, wind turbines, diesel generators, energy storage) and also the random natural factors significantly influencing its functioning, such as wind, solar radiation and cloudiness is provided in a software complex.
The key indicators of efficiency are the cost of acquisition, deployment and operation of system, and reliability (continuity) of supply to the consumer the necessary energy.
The developed simulation models allow to obtain more exact and approximate to real conditions of operation, results, when forming stand-alone system from the existing components for specific consumers taking into account amount of the energy consumed by them, geographical and climatic features.
The description of structure of the software complex that implements decision support system and reflect interaction of system components with each other and with factors of external environment is also submitted in the paper. Layouts of the interface of the program and numerical results received by means of DSS are given.
The decision support system is supposed to be used for an assessment of efficiency and comparison of various options of creation of stand-alone energy systems and formulation of recommendations about its application, including in aerospace industry.
Keywords: decision support system, simulation modeling, stand-alone energy systems