Post stall maneuver control of advanced fighter considering the unsteady aerodynamics

Abstract

This paper focuses on the problems of unsteady aerodynamic modeling and flight control during post stall maneuver. Firstly, considering serious nonlinearity, coupling and hysteresis of aerodynamic force when advanced fighter aircraft doing post stall maneuver, we propose the strategy of using the extreme learning machine (ELM) method to model the unsteady aerodynamics and using dynamic inversion method to design the control law. Secondly, the angle of attack and sideslip angle and other states variables are obtained and selected as input variables based on wind tunnel test data. And coefficients of aerodynamics force are chosen as output variables. The wind tunnel data is divided into two groups: training samples and testing samples. Then ELM method is used to establish accurate unsteady aerodynamic model. The model accuracy is tested by the determination coefficient based on testing samples, which determines parameters of ELM. Thus problem of ignoring the unsteady aerodynamic in traditional control is avoided. After that, dynamic inversion method and daisy chain distribution method based the control law of advanced fighter are designed, and the alternative formula of reduced frequency is derived. Finally, compared with result of steady aerodynamic modeling, simulations of typical cobra maneuver by unsteady aerodynamics show significance of taking consideration of unsteady aerodynamic effect during the post stall maneuver.