VESTNIK of Samara University. Aerospace and Mechanical EngineeringVESTNIK of Samara University. Aerospace and Mechanical Engineering2542-04532541-7533Samara National Research University522810.18287/2541-7533-2017-16-3-65-75НеопределенSet-theory model of the aircraft hydraulic system working fluid stateKoptevA. N.<p><span lang="EN-US">Doctor of Science (Engineering), <br />Professor of the Department of Aircraft Maintenance</span></p>eat@ssau.ruGareyevA. M.<p><span lang="EN-US">Candidate of Science (Engineering), <br />Associate Professor of the Department of Aircraft Maintenance</span></p>gareevalbert@mail.ruPopelnyukI. A.<p><span lang="EN-US">postgraduate student of the Department of Aircraft Maintenance</span></p>osni204@yandex.ruSamara National Research University2311201716365752311201723112017Copyright © 2017, VESTNIK of Samara University. Aerospace and Mechanical Engineering2017<p><span lang="EN-US">The article is devoted to the development of a set-theory model of the aircraft hydraulic system working fluid state using the mathematical apparatus of the set theory. The relevance of the work is connected with the necessity of developing a universal mathematical model of the hydraulic fluid state. The model is to form the basis of an intelligent system to control the working fluid state on board the aircraft. As a result, a general expression is obtained that allows describing the working fluid state at an arbitrary moment of time using its basic parameters, namely contamination, viscosity, density, chemical and temperature properties. A hierarchy of parameters of the working fluid state taking into account the diagnostic value of the information obtained during their measurement is constructed. The main classes of states are distinguished among all possible states of the working fluid. These are the ideal state, the normal state, pre-failure and failure. Each of them is described by a set of configurations of all possible values of the main parameters. </span>А<span lang="EN-US"> technique for optimizing the time of the inspection of technical condition based on the calculation of the change in the entropy of the working fluid is proposed.</span></p>Воздушное судногидравлическая системаконтроль технического состояниярабочая жидкостьматематическая модельэнтропиятеория множествтеория распознавания образовAircrafthydraulic systemcondition monitoringworking fluidmathematical modelentropyset theorytheory of pattern recognition[1. Mesarovic M.D., Takahara Ya. General systems theory: mathematical foundations. New York: Academic Press., 1975. 322 p.][2. Grenander U. Lectures in pattern theory. V. 1. Pattern Synthesis. New York: Springer-Verlag, 1976. 609 p.][3. Koptev A.N., Gareyev A.M., Popelnyuk I.A. Prospective lines of improving the process of evaluating the technical condition of aircraft hydraulic system working fluid. Vestnik of Samara University. Aerospace and Mechanical Engineering. 2017. V. 16, no. 1. P. 101-108. (In Russ.). DOI: <a href='http://doi.org/10.18287/2541-7533-2017-16-1-101-108'>10.18287/2541-7533-2017-16-1-101-108</a>][4. Stoll R.R. Sets, Logic and Axiomatic Theories. San Francisco, 1961.][5. GOST 17216-1971. Industrial purity. Grades of liquids purity. Moscow: Standartinform Publ., 2008. 13 p.][6. Fu K.S. Syntactic methods in pattern recognition. New York: Academic Press, 1974. 306 p.]