scholarly journals Background for modeling the dynamic characteristics of advanced spacecraft drives considering the operation of oscillators

2020 ◽  
Vol 19 (4) ◽  
pp. 317-327
Author(s):  
A. N. Sova ◽  
M. I. Stepanov ◽  
V. A. Sova ◽  
A. I. Bykov
Keyword(s):  
Dynamic Characteristics ◽  
Position Control ◽  
Experimental Testing ◽  
Experimental Studies ◽  
Space Vehicle ◽  
Point Of View ◽  
Space Vehicles ◽  
Stabilization Control ◽  
Processing Data ◽  
Algorithmic Support

Introduction. Precision elements of the target equipment and sensitive elements of the stabilization and orientation system of the advanced spacecraft are considered in the framework of this research. A method and software for modeling the dynamic characteristics of these elements are developed and validated. At that, the processing data results from the experimental studies on active and passive oscillators are taken into account.Materials and Methods. It is shown how the method of weightlessness provides simulation of the conditions that as much as possible conform to the real-time use of advanced space vehicles, precision structural elements, target equipment and their drives. Schemes of the corresponding experimental facilities are presented. Mathematical modeling methods, techniques of machine mechanics and dynamics are applied. Basic parameters of the proposed design dynamics, which are governing parameters in terms of the implementation of the target functions of the spacecraft, are calculated. Rational versions of layout and approximate cycle patterns of the operation of advanced space vehicles are formed to reduce microperturbations from driving gear with rotating masses.Research Results. A simulation technique for the dynamic characteristics of the drives of advanced space vehicles considering the regular oscillator operation is developed and validated. A complex of methods is presented for solving the problems of identifying dynamic parameters of a mathematical model of an advanced spacecraft based on the processing data results obtained through the experimental testing of active and passive oscillators. Two types of vibration from flywheel engines are noted. The first type is according to the commands of the position control and stabilization control system. The second type is due to residual imbalance from the solar constant meter. It is shown how these vibrations affect the dynamic characteristics of the gyro mounting seats and of the multispectral scanner for hydrometeorological support of the spacecraft. The data obtained are meant to solve the problems of assurance of the dynamic accuracy of advanced space vehicles.Discussion and Conclusions. A technique for modeling the dynamic characteristics of advanced space vehicles when operating in the precision orientation mode is proposed. The solution is based on the results of theoretical and experimental studies presented in the paper, and it considers the operation of standard oscillators. The implementation of this method is brought to software and algorithmic support for assessing the dynamic characteristics of standard oscillators of an advanced space vehicle. Recommendations to reduce the effect of active oscillators are established. Initial data are selected to determine the dynamics of advanced space vehicles from the point of view of fulfilling their target functions. The layout and approximate cycle patterns of the operation of advanced space vehicles to identify the driving gear with rotating masses as sources of micro-perturbations are proposed.

Relativistic synchronization of onboard clocks of navigation space vehicles with the aid of intersatellite measurements

2021 ◽  
pp. 56-66
Author(s):  
Nikolay N. Vasilyuk ◽  
Alexander P. Chervonkin
Keyword(s):  
Proper Time ◽  
Space Vehicle ◽  
Relativistic Correction ◽  
Point Of View ◽  
Space Vehicles ◽  
Satellite Measurements ◽  
Clock Drift ◽  
Coordinate Time ◽  
Upper Limit ◽  
Unambiguous Interpretation

The problem of the synchronization of onboard clocks of navigation satellites has considered from a relativistic point of view using the concept of “coordinate simultaneity”. This concept allows an unambiguous interpretation of the synchronization results within the framework of general relativity. The algorithm of intersatellite measurements processing has formulated in terms of a proper time of a space vehicle and the coordinate time of a reference frame. Rules of transformation between coordinate and proper time scales have indicated. An analytical expression has obtained for the periodic relativistic correction to the estimated value of the relative clock drift. This correction has expressed in terms of the coordinate time of a ground observer. The value of this correction exceeds the acceptable synchronization error and should be taken into account for the inter-satellite measurements processing. The error of the relativistic correction determination has calculated. This error provides an upper limit for the period of uploading of ephemeris data on the board of the space vehicle.

Masonry: the brittle or plastic material?

2019 ◽  
pp. 22-28
Keyword(s):  
Plastic Material ◽  
Experimental Studies ◽  
Point Of View ◽  
Plastic Properties ◽  
Plastic Deformations ◽  
Base Materials ◽  
Stress States ◽  
Creep Deformations ◽  
Structural Point

The results of experimental studies of masonry on the action of dynamic and static (short-term and long-term) loads are presented. The possibility of plastic deformations in the masonry is analyzed for different types of force effects. The falsity of the proposed approach to the estimation of the coefficient of plasticity of masonry, taking into account the ratio of elastic and total deformations of the masonry is noted. The study of the works of Soviet scientists revealed that the masonry under the action of seismic loads refers to brittle materials in the complete absence of plastic properties in it in the process of instantaneous application of forces. For the cases of uniaxial and plane stress states of the masonry, data on the coefficient of plasticity obtained from the experiment are presented. On the basis of experimental studies the influence of the strength of the so-called base materials (brick, mortar) on the bearing capacity of the masonry, regardless of the nature of the application of forces and the type of its stress state, is noted. The analysis of works of prof. S. V. Polyakov makes it possible to draw a conclusion that at the long application of the load, characteristic for the masonry are not plastic deformations, but creep deformations. It is shown that the proposals of some authors on the need to reduce the level of adhesion of the mortar to the brick for the masonry erected in earthquake-prone regions in order to improve its plastic properties are erroneous both from the structural point of view and from the point of view of ensuring the seismic resistance of structures. It is noted that the proposal to assess the plasticity of the masonry of ceramic brick walls and large-format ceramic stone with a voidness of more than 20% is incorrect, and does not meet the work of the masonry of hollow material. On the basis of the analysis of a large number of research works it is concluded about the fragile work of masonry.

Analysis of the results of medium-energy electrons on the protective and thermoregulatory coatings of high-orbit satellites

2018 ◽  
pp. 156-171
Author(s):  
A. M. Shamayev ◽  
M. D. Ozersky
Keyword(s):  
Structural Changes ◽  
Protective Coatings ◽  
Experimental Studies ◽  
Thermal Control ◽  
Space Vehicles ◽  
Medium Energy ◽  
Electrostatic Discharges ◽  
High Orbit ◽  
Thermal Control Coatings ◽  
Solar Batteries

The results of experimental studies of the effect of electron irradiation on K-208 and CMG glasses used for manufacturing protective coatings of solar batteries and thermal control coatings of space vehicles are analyzed. It is shown that the caused electrostatic discharges lead to structural changes in the surfaces of the glasses studied. The goals of further studies of the influence of proton and electronproton effects on the properties of such coatings are outlined. 

On-Site Experimental Testing to Study the Vibration of Composite Floors

2014 ◽  
Vol 601 ◽  
pp. 231-234
Author(s):  
Cristian Lucian Ghindea ◽  
Dan Cretu ◽  
Monica Popescu ◽  
Radu Cruciat ◽  
Elena Tulei
Keyword(s):  
Dynamic Characteristics ◽  
Experimental Testing ◽  
Concrete Slab ◽  
Human Perception ◽  
Experimental Tests ◽  
International Standards ◽  
Structural Element ◽  
Element Analysis ◽  
Floor Slabs ◽  
Composite Floors

As a general trend, in order to reduce material consumption or to reduce the mass of the structures, composite floor slabs solutions are used to achieve large spans floor slabs. This solutions led to floors sensitive to vibrations induced generally by human activities. As a verification of the design concepts of the composite floors, usually, it is recommended a further examination of the floor after completion by experimental tests. Although the experimental values of the dynamic response of the floor are uniquely determined, the processing can take two directions of evaluation. The first direction consist in determining the dynamic characteristics of the floor and their comparison with the design values. Another way that can be followed in the processing of the experimental results is to consider the human perception and comfort to the vibration on floors. The paper aims to present a case study on a composite floor, with steel beams and concrete slab, tested on-site. Both aspects of data processing are analyzed, in terms of the structural element, and in terms of the effect on human perception and comfort. Experimentally obtained values for the dynamic characteristics of the floor are compared with numerical values from finite element analysis, while the second type of characteristic values are compared with various human comfort threshold values found in international standards.

A Research for Angle Optimization of the SRM Used in Electric Actuator of Valves

2013 ◽  
Vol 404 ◽  
pp. 586-591
Author(s):  
Ding Hong Yang Yang ◽  
Dean Zhao ◽  
Ying Xin Jiang
Keyword(s):  
High Speed ◽  
Position Control ◽  
Experimental Testing ◽  
Optimal Switching ◽  
Switched Reluctance ◽  
Electric Actuator ◽  
Turn On ◽  
Reluctance Motor ◽  
Two Parameters ◽  
Theory Research

This paper uses TMS320F28335 DSP and MAX3032S CPLD as the controller of the 6/4 pole switched reluctance motor (SRM), and controls the motor by the method of current chopping control (CCC) in low speed and the method of angle position control (APC) in high speed. About the optimization of turn-on angle and turn-off angle when SRM is controlled by the method of APC, this paper discusses the optimal design of the two parameters by ways of theory research, simulation and experimental testing. The results show optimal switching angle can make speeded-up of the motor better and improve the performance of SRM.

INFLUENCE OF TECHNOLOGICAL FACTORS ON THE EFFICIENCY OF REMOVAL OF SCALE FROM FLATS FOR HOLLOW BALLS

2021 ◽  
pp. 143-147
Author(s):  
А.В. Панфилова ◽  
А.В. Королев ◽  
О.П. Решетникова ◽  
Б.М. Изнаиров ◽  
А.Н. Васин
Keyword(s):  
Rotation Speed ◽  
Experimental Studies ◽  
Surface Cleaning ◽  
Point Of View ◽  
Design Parameters ◽  
Technological Factors ◽  
Proportional Relationship ◽  
Sheet Products ◽  
Process Factors ◽  
Rolled Surface

Рассматриваются результаты проведения экспериментальных исследований способа удаления окалины с поверхности стального листового проката. Предложен новый способ и устройство для очистки поверхности листового проката от окалины режущими пластинами, вращающимися вокруг оси, перемещающейся поступательно вдоль обрабатываемой поверхности. Пластины наклонены в направлении вектора вращения на угол до 10 градусов и упруго поджимаются к обрабатываемой поверхности. Это обеспечивает возможность в процессе очистки поверхности воспроизводить макронеровности листового проката. Приведены результаты экспериментальных исследований, построены математические и графические зависимости, описывающие влияние факторов процесса на эффективность очистки поверхности проката. Показано, что наиболее значимое влияние на параметр оптимизации оказывает сила воздействия инструмента на поверхность заготовки. Причем это влияние реализуется в прямо пропорциональной зависимости. Другие исследованные факторы, а именно: угол наклона пластины, скорость ее вращения и подача, оказывают значительно меньшее влияние на степень очистки проката. Эти исследования были необходимы с точки зрения определения конструктивных параметров силовых элементов как технологической оснастки, реализующей указанный способ, так и технологической установки в целом. План эксперимента был принят, исходя из реальных производственных возможностей индустриального партнера, и соответствовал классическим представлениям теории резания. Описанные результаты дают возможность планировать дальнейшие эксперименты по изучению направлений использования данного способа Here we consider the results of experimental studies of the method of removing scale from the surface of steel sheet products. We propose a new method and device for cleaning the surface of rolled sheets from scale by cutting plates rotating around an axis moving translationally along the treated surface. The plates are tilted in the direction of the rotation vector at an angle of up to 10 degrees and are elastically pressed to the treated surface. This makes it possible to reproduce the macro-dimensions of sheet metal during the surface cleaning process. We present the results of experimental studies. We constructed mathematical and graphical dependences describing the influence of process factors on the efficiency of cleaning the rolled surface. We show that the most significant influence on the optimization parameter is exerted by the force of the tool's impact on the surface of the workpiece. Moreover, this influence is realized in a directly proportional relationship. Other factors studied, namely the angle of inclination of the plate, its rotation speed and feed, have a much smaller impact on the degree of cleaning of rolled products. These studies were necessary from the point of view of determining the design parameters of the power elements of both the technological equipment implementing this method and the technological installation as a whole. We adopted the experimental plan based on the real production capabilities of the industrial partner and corresponded to the classical concepts of the cutting theory. The described results make it possible to plan further experiments to study the directions of using the method

Crashworthiness Performance of Mass-Efficient Extruded Structures

2002 ◽  
Author(s):  
Robert R. Mayer ◽  
Weigang Chen ◽  
Anil Sachdev
Keyword(s):  
Numerical Simulations ◽  
Single Cell ◽  
Experimental Testing ◽  
Experimental Studies ◽  
Nonlinear Material ◽  
Dynamic Strain ◽  
Cell Design ◽  
Explicit Finite Element ◽  
The One ◽  
Crushing Behavior

Theoretical, numerical and experimental studies were conducted on the axial crushing behavior of traditional single-cell and innovative four-cell extrusions. Two commercial aluminum alloys, 6061 and 6063, both with two tempers (T4 and T6), were considered in the study. Testing coupons taken from the extrusions assessed the nonlinear material properties. A theoretical solution was available for the one-cell design, and was developed for the mean crushing force of the four-cell section. Numerical simulations were carried out using the explicit finite element code LS-DYNA. The aluminum alloy 6063T4 was found to absorb less energy than 6061T4, for both the one-cell and four-cell configurations. Both 6061 and 6063 in the T6 temper were found to have significant fracture in the experimental testing. Theoretical analysis and numerical simulations predicted a greater number of folds for the four-cell design, as compared to the one-cell design, and this was confirmed in the experiments. The theoretical improvement in energy absorption of 57% for the four-cell in comparison with the one-cell design was confirmed by experiment. The good agreement between the theoretical, numerical and experimental results allows confidence in the application of the theoretical and numerical tools for both single-cell and innovative four-cell extrusions. It was also demonstrated that these materials have very little dynamic strain rate effect.

Recurrent Neural Networks with Small Weights Implement Definite Memory Machines

2003 ◽  
Vol 15 (8) ◽  
pp. 1897-1929 ◽  
Author(s):  
Barbara Hammer ◽  
Peter Tiňo
Keyword(s):  
Neural Networks ◽  
Recurrent Neural Networks ◽  
Experimental Studies ◽  
Activation Function ◽  
Transition Function ◽  
Recurrent Network ◽  
Point Of View ◽  
Recurrent Networks ◽  
Contraction Parameter ◽  
Arbitrary Precision

Recent experimental studies indicate that recurrent neural networks initialized with “small” weights are inherently biased toward definite memory machines (Tiňno, Čerňanský, & Beňušková, 2002a, 2002b). This article establishes a theoretical counterpart: transition function of recurrent network with small weights and squashing activation function is a contraction. We prove that recurrent networks with contractive transition function can be approximated arbitrarily well on input sequences of unbounded length by a definite memory machine. Conversely, every definite memory machine can be simulated by a recurrent network with contractive transition function. Hence, initialization with small weights induces an architectural bias into learning with recurrent neural networks. This bias might have benefits from the point of view of statistical learning theory: it emphasizes one possible region of the weight space where generalization ability can be formally proved. It is well known that standard recurrent neural networks are not distribution independent learnable in the probably approximately correct (PAC) sense if arbitrary precision and inputs are considered. We prove that recurrent networks with contractive transition function with a fixed contraction parameter fulfill the so-called distribution independent uniform convergence of empirical distances property and hence, unlike general recurrent networks, are distribution independent PAC learnable.

Sézary, A. et Friedmann, E. Duration of incubation in Nicolas-Favre disease. (Bull. Soc. Fr. Derm, et Syph., No. 8, 1936)

1937 ◽  
Vol 33 (7) ◽  
pp. 937-937
Keyword(s):  
Incubation Period ◽  
Experimental Studies ◽  
Point Of View ◽  
Case Histories

In recent years, the authors have observed more than 100 cases of lymphogranulomatosis. The greatest interest from the point of view of studying the duration of the incubation period in this disease deserves 11 cases, the case histories of which the authors cite in brief excerpts. In 8 cases, incubation was equal to one month, in 1 case 1 months and in 2 cases 3 months. The most probable and plausible period is 1 month. Experimental studies on animals show that they have an average incubation of 35 days. Touraine, in a debate on the authors' report, indicated that in the classical manuals and from his personal observations, the incubation period of the disease is 10-25 days.

Лексическая неоднозначность в экспериментальных исследованиях: метаанализ

2020 ◽  
pp. 43-51
Author(s):  
Анжелика Дубасова
Keyword(s):  
Language Processing ◽  
Ambiguity Resolution ◽  
Experimental Studies ◽  
Lexical Ambiguity ◽  
Point Of View ◽  
Lexical Ambiguity Resolution ◽  
Ambiguous Words ◽  
Main Factors ◽  
The Difference ◽  
The Right

The article analyses experimental studies of lexical ambiguity (polysemy and homonymy). In total, 42 papers published between 1981 and 2017 were selected for analysis. Selected works were analyzed from the point of view of a) interaction of the main factors of lexical ambiguity resolution (meaning dominance and context), b) modularity/interactivity of language systems. The choice of these issues was caused by the fact that, despite a significant number of papers addressing them, a common theoretical model of lexical ambiguity resolution is still missing. The analysis concluded that none of the existing models could be chosen as the only true one. I believe that it is more promising to combine all models into one; in this case, we should not talk about “models” but about “algorithms” or “strategies”. This merge is compatible with the results of studies of hemispheric asymmetry, which showed that the right and left hemispheres differently process ambiguous words. This difference is projected on the difference between the two main points of view on language processing, interactive and modular. Also, as a result of the analysis, the properties of meaning dominance and context as the main factors influencing the perception of ambiguity are summarized, and the ways and possibilities of their interaction are determined. These factors can participate in the process of resolving ambiguity autonomously or together, with different functions, speed, and levels of perception.

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