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Technical Paper

Technology of Cut-Glue Approximation Method for Modeling Strongly Nonlinear Multivariable Objects. Theoretical Bases and Prospects of Practical Application

2016-09-20
2016-01-2035
The main difficulties of the mathematical models vehicles creation are defined by strongly nonlinearity of dependences which connect various variables their states and conditions of the movement environment. Most it belongs to aircrafts as aerodynamic interactions are characterized by essential nonlinearity up to discontinuity of variables and their derivatives. Creation process of these models is complicated by high-dimensionality, characteristic for the mechanical movement laws. Experimental creation of the mathematical models (MM) of such dependences is carried out by various mathematical methods of approximation of data. Universal remedies of the solution of the formulated task don't exist. Each of it possesses both benefits, and considerable shortcomings. In this regard the possibilities of a method creation of high-precision analytical approximations of the strongly nonlinear dependences using the analytical functions have been investigated.
Journal Article

Bivariate “Cut-Glue” Approximation of Strongly Nonlinear Mathematical Models Based on Experimental Data

2015-09-15
2015-01-2394
Researchers meet the difficulties of experimental and computer modeling of a statics and dynamics of aircrafts connected with their essential nonlinearity. This is due to the fact that the aerodynamic effects of the interaction complex aircraft designs or their models with air environment generate abrupt changes of the character of the some dependencies. Aerodynamic coefficients in the model of interaction can be obtained only or by full-scale tests or by computer simulations. Therefore, the construction of mathematical models of the objects is associated with the mathematical processing of the points of the experimental data. In this case, the experimentally obtained dependence is usually essentially nonlinear up to piecewise, or even discontinuous nature. Approximation of such dependencies, even with the use of spline functions, is very difficult and is associated with large errors.
Technical Paper

Synthesis of Time Quasi-Optimal Asymptotically Stable Control Laws

2015-09-15
2015-01-2481
The solution of the both synthesis and implementation problems of high-rapid rates control laws is extremely important for the development of automatic control systems of the aircraft. This is due to the high speed of such vehicles. Along with this, it is imperative that control laws provide that system is asymptotically stable, as the basis for the reliability of their controlled motion. Another important objective of the method of synthesis of control laws for aircraft is compulsory compliance with strict limitations on the values of control inputs at the actuation devices. It is equally important that the control laws provides limitations on the state variables of aircraft, such as velocity, acceleration, etc. Pontryagin's maximum principle is aimed at solving such a time-optimal problem with the limited command variable.
Technical Paper

Identification of Traction and Power Characteristics of Air-Screw Propulsors in Mathematical Description of Airship

2014-09-16
2014-01-2134
The paper formulated and solved the problem of investigating the traction and power characteristics of air-screw propulsor for airships. The study is performed by constructing a mathematical model relating the steady-state values of the shaft power and traction on the axis of the screw with the velocity of rotation and the actual velocity of the aircraft. Proved design scheme selection of computer simulation of aero-and thermodynamic processes occurring during rotation of the airscrew. Describes plan developed under the experimental task, providing variation in the basic parameters of the airscrew, motion parameters and flight environment The results of computer modeling of the interaction of the airflow with the airscrew at various combinations of these parameters. Results are shown in tabular and graphical form and as a mathematical model of the studied airscrew.
Technical Paper

Aerostatic Aircraft Flight Environment Modeling and Investigation

2014-09-16
2014-01-2147
Airship dimensions define the application of the computer modeling methods under their development and investigation. Herein, the need to simulate the flight environment state - the atmospheric conditions of their traffic route - arises. The atmospheric parameters have both regular and random components, which is due to the nonstationarity of the atmospheric phenomena. Hence, it is essential to define the actual ranges, and the representative values of the atmospheric effects. Weather data are used for the analysis and the airflow performance computation in the operational area. Through their statistical processing, we need to obtain the most informative characteristics of the weather conditions in whole, and of their trends. The investigation has shown that the weather data gathering system is nonperfect. The sampling frequency is irregular and not high, test values in the specific parameters are obtained asynchronously.
Technical Paper

Airship Positioning Fuzzy Multi-Ballonet Control Study

2014-09-16
2014-01-2146
Airship designers research application versions of systems with several ballonets for adjustment of airship roll and/or pitch as a whole. This requires effective automatic status management of each separate ballonet. But multi-ballonet system control issue encounters the absence of industrially measurable variables of each separate ballonet status. Thus status control issue of the system becomes uncertain. The fact requires the issue studying and shaping new scientific and technical solutions. This publication represents research results implying that fairly simple implementation and effective result can be achieved by application of fuzzy control concept. Its application is built on generating the representative quantity of fuzzy production rules. They are based on present set evaluation of known parameters and measured variables. This results in fuzzy but meaningful image of ballonet system status and airship as a whole. Thus achieving fairly good control over multi-ballonet system.
Technical Paper

Stability Analysis of the MAAT Feeder Airship During Ascent and Descent with Wind Disturbances

2013-09-17
2013-01-2111
This paper looks into with the aerodynamic properties and stability of the feeder airship in the framework of MAAT project. FP7 MAAT project is based on the concept of two different types of airships (the cruiser and the feeder) working together as a transportation system. The feeder considered in this paper is a rigid airship with an unconventional envelope shape. Aerodynamic forces and moments acting on the airship during the horizontal and vertical flight modes are of special interest in this study, because the aerodynamic performance of the aircraft directly influences its general dynamic behavior and, thus, its in-flight stability. A set of CFD simulations was conducted for vertical and horizontal flights of the feeder airship. Drag and lift forces and pitching moment together with their coefficients, were obtained for different altitudes and velocities from the proposed operational ranges of the airship.
Technical Paper

Aerodynamic Characteristics Study and Possible Improvements of MAAT Feeder Airships

2013-09-17
2013-01-2112
This paper is dedicated to the study and improvement of the aerodynamic properties of the feeder airship in the context of MAAT project. FP7 MAAT project is based on the concept of two different types of airships (the cruiser and the feeder) working together as a transportation system. The current feeder concept includes unconventional shape changing envelope. Two problems are considered in this paper. The first problem is to find a condition of the effective vertical ascent for the feeder (from the ground to the altitude of the cruiser). A series of CFD simulations were carried out for the top flow for a range of altitudes from 0 to 16 km and velocities between 2 and 10 m/s. The results confirm the appearance of some negative effects, including high drag during the vertical ascent, especially, at low altitudes. The second problem is to study and reduce the side wind effects on the ascending feeder airship.
Journal Article

Continuous-Positional Automatic Ballonet Control System for Airship

2013-09-17
2013-01-2236
This paper is devoted to a method of creating of the automated ballonet system for pressure control inside an airship envelope. Along with the study of the effects of the positional control system parameters, the authors develop novel control scheme. It is based on a new hybrid controller, which combines positional approach to forming the output control signal with a contour of continuous correction of input signal, which defines the pressure drop on the surface of the envelope as a function of the flight altitude. This approach allows reducing the effect of self-oscillations of airship envelope internal pressure on the flight altitude. In order to prove the new approach the mathematical model is being obtained. The results of the derivation and simulations of the control system operation are presented in this paper.
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