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Synthesis of nonlinear controller to recover an unstable aircraft from poststall regime

Saraf, Amitabh and Deodhare, Girish and Ghose, Debasish (1999) Synthesis of nonlinear controller to recover an unstable aircraft from poststall regime. In: Journal of Guidance, Control, and Dynamics, 22 (5). pp. 710-717.

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Dynamics of the aircraft configuration considered in this paper show a unique characteristic in that there are no stable attractors in the entire high angle-of-attack flight envelope. As a result, once the aircraft has departed from the normal flight regime, no standard technique can be applied to recover the aircraft. In this paper, using feedback linearization technique, a nonlinear controller is designed at high angles of attack, which is engaged after the aircraft departs from normal flight regime. This controller stabilizes the aircraft into a stable spin. Then a set of synthetic pilot inputs is applied to cause an automatic transition from the spin equilibrium to low angles of attack where the second controller is connected. This controller is a normal gain-scheduled controller designed to have a large domain of attraction at low angles of attack. It traps the aircraft into a low angle-of-attack level flight. This entire concept of recovery has been verified using six-degrees-of-freedom nonlinear simulation. Feedback linearization technique used to design a controller ensures internal stability only if the nonlinear plant has stable zero dynamics. Because zero dynamics depend on the selection of outputs, a new method of choosing outputs is described to obtain a plant that has stable zero dynamics. Certain important aspects pertaining to the implementation of a feedback linearization-based controller are also discussed.

Item Type: Journal Article
Publication: Journal of Guidance, Control, and Dynamics
Publisher: American Institute of Aeronautics and Astronautics
Additional Information: Copyright of this article belongs to American Institute of Aeronautics and Astronautics.
Department/Centre: Division of Mechanical Sciences > Aerospace Engineering(Formerly Aeronautical Engineering)
Date Deposited: 01 Jul 2011 05:17
Last Modified: 01 Jul 2011 05:17
URI: http://eprints.iisc.ac.in/id/eprint/38832

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