Vol 17, No 1 (2018)

The task of optimizing trans-atmospheric motion of a flight vehicle in order to maximize its final velocity with prescribed finite values of the height and flight path angle is considered. The angle of attack acts as control in passive motion of a vehicle. Previously, the sequential linearization method was used to solve this optimization task. It is shown that at great altitudes the control programs are slightly different depending on the chosen initial approximation.  Therefore, the aim of this work is to determine the optimum control program on the basis of a “strict” solution of the optimization task using the Pontryagin’s maximum principle. Solving the problem of optimizing trans-atmospheric motion of a flight vehicle is illustrated by passive climb of the sub-hypersonic vehicle MPV (the first stage of the aerospace system RASCAL designed in the USA). The coefficient of lift (angle of attack) increases in the greater part of the trajectory to provide the prescribed finite values of height and path inclination and then decreases to provide maximum final velocity. The correctness of the obtained solutions of the optimization task using the maximum principle is confirmed by the zero Hamiltonian value in the optimum trajectory. The results of vehicle motion simulation with optimal control and various initial conditions of motion and the vehicle mass are discussed. The results obtained show that the solutions of the optimization task under consideration using the maximum principle and the sequential linearization principle are in close agreement.

A Strapdown Inertial Measurement Unit (SIMU) with structural redundancy intended for improving fault-tolerance and accuracy of inertial navigation systems for space applications is considered. The SIMU includes six angular rate sensors and six accelerometers, which allows for identification and correction of one fault with high probability and two faults with lower probability for each type of sensor. Known theoretical and practical techniques developed and used in this area are briefly described. The problem of optimization of measurement axes orientation is considered. The accuracy of estimation of the measured vector projections in the orthogonal instrument coordinate system serves as the criterion of optimization. A solution of this problem for no faults, one fault, and two faults is proposed. Algorithms of failure detection, identification and correction (FDIC) are analyzed. The results of testing FDIC basic algorithms with the help of mathematical simulation are considered. Optimal measurement axes configurations are compared with each other from the FDIC efficiency point of view. It is shown that neither of the methods yields 100-percent correct diagnostics not only for two faults but for one fault as well. Possible sources of incorrect diagnostics are analyzed.

Unmanned aerial vehicles have enormous potential and prospects in expanding the field of application from photo and video to providing cellular communications and relaying signals. An atmospheric pseudo satellite that is expected to function exclusively at the expense of solar energy is being developed at S.P. Korolyov Samara National Research University. A study of the efficiency of using photoelectric converters in the onboard equipment of an atmospheric pseudo satellite based on the unmanned aerial vehicle Foton-601 was carried out. A comparative analysis of various types of photovoltaic converters made of amorphous silicon was performed. A mathematical model was developed and the area of solar cells coating required to generate sufficient power was calculated. The mass of the solar cells for the appropriate coating area was calculated. Also, in order to reduce the mass of an unmanned aerial vehicle and, as a result, its energy consumption, a method of mathematical calculation to determine minimum and sufficient required battery capacity was developed, on the basis of the maximum amount of solar energy that can be converted within 24 hours. The results of flight tests were analyzed and the prospects for the use of photoelectric converters as components  of solar cells of atmospheric pseudo satellites were specified.

When developing counter-rotating fans for advanced aircraft engines with ducted blades (CRTF), it is very important to ensure high acoustic and aerodynamic characteristics. To provide investigations of aerodynamic and acoustic performance of the original version of an advanced counter-rotating CRTF1 fan model with  in the C-3A anechoic chamber (CIAM), its experimental and mathematical models were developed and 3D steady viscous flow and integral characteristics were calculated. The paper presents a comparison of data computed by “mixing plane” approximation and the experimental CRTF1 data. This comparison shall demonstrate the validity of designing the CRTF2A second version without taking unsteady interaction into consideration. These comparisons of computed and measured data give evidence of good agreement at . The degree of coincidence between the computed and experimental data at  is satisfactory – maximum error is <2%. This paper presents some results of gasdynamic and aeroacoustic optimization of the configuration of a ducted fan carbon composite blade on the basis of the solution of a 3D-inverse problem [3]. A distinctive feature of a carbon composite blade as compared with a solid titanium blade is thicker leading and trailing edges and increased maximum blade profile thickness.

The article deals with the problems of choosing materials for producing dimensionally stable load-carrying structures of space optical electronic complexes. Physical and mechanical properties of successfully applied and promising composite materials obtained by theoretical and experimental research are presented. A comparative analysis of properties of carbon-filled plastics is given according to the percentage of filler content in a composite matrix and the elastic modulus of carbon fiber. Experimental data related to the properties of carbon-filled plastics based on various fibers are presented. The dependence of the temperature coefficient of linear expansion (TCLE) of various carbon-filled plastics with unidirectional and quasi-isotropic structures is studied theoretically and experimentally. The stability of TCLE is shown to be approximately equal to 1·10^-6 ˚C^-1 in the area with 50-60% volume filler content. The TCLEs and elastic moduli of carbon-filled plastics and optical glasses of telescope elements are compared. The task of developing a composite material with a TCLE value characteristic of titanium alloys is discussed. Recommendations for applying the analyzed composite materials in the development of dimensionally stable space structures are given.

The dependence of low-cycle and high-cycle fatigue characteristics of threaded parts on the criterion of average integral residual stresses is examined in the article. These characteristics play an essential role in ensuring reliability of aeronautical equipment. The study was carried out using titanium-alloy M6 bolts with various ways of producing residual stresses. In all the cases the dependences are quadratic. Further analysis showed linear dependence between the increment of cycle life and the limiting cycle amplitude under changes of residual stresses. This conclusion holds for all examined ways of producing residual stresses. The increments mentioned are linear functions of the criterion of average integral residual stresses. A procedure for determining the increment of the limiting cycle amplitude with the use of the criterion of average integral stresses is presented. Special attention is given to the method of finding the coefficient of residual stress influence on the limiting cycle amplitude for the constant mean stress. The approach to determining the increment of cycle life by a known value of the increment of the limiting cycle amplitude calculated with the use of the criterion of average integral residual stresses is validated.

Significant improvement of dynamic characteristics of vibration machines on the basis of the use of resonant oscillatory systems with two or more degrees of freedom is proposed. It is shown that reasonable complication of models due to the increase in the number of degrees of freedom, taking account of nonlinearity makes it possible to increase reciprocal enhancement of vibrations of partial subsystems and to open additional opportunities in the development of new equipment and technologies. The involvement of objects of an oscillatory system in collective interaction is achieved on the basis of using compound resonances which occur in coupled systems only. Combination parametric resonance caused by pair-wise interaction of free modes of oscillations represents this kind of resonance. The results of theoretical and experimental studies of self-synchronization of parametric rotor-pendulum vibration generators installed on a common elastic isotropic foundation are presented in the paper. The dynamic model of a vibration machine is represented by a set of peer interacting nonlinear oscillators (pendulums) under resonant excitement of which the Huygens's effect, that is, pendulum clock-type self-synchronization (pendulum self-synchronization) occurs. One or several oscillators perform the functions of the working body of the vibration machine. Other oscillators of this system act as the inertial element of a rotor-pendulum vibration generator. It is shown that in the case of combined action of at least two rotors-pendulum vibration generators unbalanced rotor-type self-synchronization (rotor self-synchronization) takes place. Thus, the device under examination at the same time combines rotor and pendulum self-synchronization. The results of numerical modeling in the form of amplitude-frequency characteristics and dependences of generation frequencies on the frequency of parametric excitation are presented. It is established that the amplitude of the working body oscillations, due to resonant interactions with the generator pendulums, underreacts to an increase in damping. The sum of natural frequencies of pendulums and the working body meets the condition of combination parametric resonance over the whole range of the instability region.

The article proposes a way of organizing and storing information to generate a multidimensional array of related current data that reflect a documented fact of performing economic operations in a common information space. The proposed method is based on structuring the data conforming to primary documents, detailed to logically complete economic operations and rigidly interconnected. The essence of the method is discussed in the paper. The experience of creating an automated control system on the basis of the developed method of organizing and storing data on economic activity is described. We propose to use the resulting array of structured data for integration with functional accounting systems to automate basic processes in enterprise management on the basis of the generated OLAP system. Examples of external influences on the automated control systems and ways of troubleshooting are described. Conclusions about the positive effect of introducing an automated system of enterprise management based on the developed method of organizing and storing actual data about purchases, sales and own expenses, as well as their relationship to functional automated systems are drawn.