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Mekhatronika, Avtomatizatsiya, Upravlenie, 2018, vol. 19, no. 3, pp. 201—208
Identification of Hysteresis Models for Aerodynamic Coefficients at Overcritical Angles of Attack
O. N. Korsun, email@example.com, A. V. Stulovsky, firstname.lastname@example.org, State Research Institute of aviation systems, Moscow, 125167, Russian Federation,
A. V. Kanyshev, email@example.com, State Flight Test Center named after V. P. Chkalov, Akhtubinsk, Russian Federation
Corresponding author: Korsun Oleg N., D. Sc., Professor, State Research Institute of Aviation Systems, Moscow, 125167, Russian Federation,
Accepted on October 27, 2017
At present, maneuverable thrust vectored aircraft are capable of performing a controlled flight beyond normal flight envelope, namely, for attack angles significantly exceeding the critical value. It is well known that in this case the aerodynamic processes fundamentally change in comparison with flight at small and average angles of attack. It is also known that the errors in the methods of computational aerodynamics and the wind-tunnel data for overcritical range increase significantly due to the essentially nonlinear and unsteady nature of the flow. Therefore, the problem of validation and estimation of aerodynamic coefficients based on the results of flight tests by methods of system identification is vital. It is obvious that agreement of aircraft dynamics models with the flight data is necessary for the development, modernization, testing, creation of simulators, investigation of flight incidents, i.e. for all the main stages of the aircraft life cycle. One of the most important poststall effects is the emergence of hysteresis in the dependences of the aerodynamic coefficients on the angle of attack. This phenomenon is due to the fact that the flow separation with increasing angle of attack and flow restoration with the subsequent decrease of the angle of attack occur asymmetrically. This effect takes place even for very small values of the derivative of the angle of attack with respect to time, and as a result it is called stationary hysteresis. This article deals with the problems concerning identification of the mathematical model for aircraft motion at the overcritical angles of attack by processing flight test data. Algorithms for obtaining estimates for coefficients of the lift force, the drag force and the pitching moment from the flight test data are proposed. The mathematical model of the hysteresis of the lift coefficient is considered, and its parameters are identified. Furthermore, article presents expressions allowing the calculation of the hysteresis of the drag coefficient and the pitch moment through the hysteresis of the lifting force and the coefficients analogous to the lift-drag ratio and static stability coefficients known from aerodynamics and flight dynamics.
Keywords: flight tests, identification of aerodynamic coefficients, aerodynamic hysteresis, thrust vectoring, overcritical angles of attack, supermaneuverability
Acknowledgements: This work is supported by RFBR grant no. 17-08-00856_a.
Korsun O. N., Stulovsky A. V., Kanyshev A. V. Identification of Hysteresis Models for Aerodynamic Coefficients at Overcritical Angles of Attack, Mekhatronika, Avtomatizatsija, Upravlenie, 2018, vol. 19, no. 3, pp. 201—208.
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