Nonlinear flight control design via sliding methods
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Nonlinear inversion/sliding control techniques are applied to design a pitch axis control system for high-performance aircraft. The control objectives are to track pilot g commands while satisfying flying quality specifications. In the pitch axis problem, the dominant nonlinearities are the aerodynamic coefficients variation with angle of attack and saturation of the actuators position and rate response. Two design approaches are investigated; the first defines a single output to be controlled (pilots normal acceleration) and coordinates the elevator and the flaperon as a single input. The nonminimum phase nature of the resulting input/output pair necessitates defining a modified output to avoid stability problems inherent in inversion methods. The second approach defines a two input/two output problem and directly incorporates the flying quality specifications into the output definition. These two methods are illustrated using a simulation model. The latter approach is shown to allow more freedom to avoid actuator saturation at high g commands. 1990 American Institute of Aeronautics and Astronautics, Inc., All rights reserved.
Journal of Guidance, Control, and Dynamics
author list (cited authors)
Hedrick, J. K., & Gopalswamy, S.