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    Automatic recovery of a combat aircraft from a completed Cobra and Herbst maneuver: A sliding mode control based scheme
    (IEEE, 2016) Mukherjee, Bijoy Krishna
    Cobra and Herbst are two complex post-stall air combat maneuvers popularly executed by the present-day fighter aircraft. At the end of these maneuvers, the aircraft usually develops either a high negative flight path angle or a high negative flight path angle rate apart from a considerably low velocity. Therefore, the aircraft needs to recover from such undesired flight conditions as quickly as possible. Usually this recovery is achieved manually by the pilot. In the present paper, a novel automatic recovery strategy is proposed. Two recovery schemes - a partial recovery scheme to get back to a level flight condition quickly without worrying about velocity and a full recovery scheme to restore the initial steady level trim completely (both velocity and altitude wise) are presented. As these maneuvers are executed in high angle of attack regions, the aircraft flight dynamics becomes highly nonlinear and coupled requiring use of nonlinear control methods. In the present work, sliding mode control technique is considered as, apart from handling the nonlinearities effectively, it also provides robustness to uncertainty in the aerodynamic data. MATLAB simulation results are presented to first demonstrate the execution of the maneuvers and thereafter to validate the proposed recovery schemes.
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    Extreme aircraft maneuver under sudden lateral CG movement: Modeling and control
    (Elsevier, 2017-09) Mukherjee, Bijoy Krishna
    Hitherto unaddressed issue of six degree-of-freedom transient dynamics during asymmetric ejection of stores with finite velocity, onboard a combat aircraft, is addressed and modeled from the first principle. Further, the effect of asymmetric center-of-gravity shift, post ejection of the store, on some complex high angle-of-attack maneuvers such as cobra and Herbst is also investigated. It is shown that the performance of the maneuvers drastically deteriorates when carried out with controller designed for the pre-ejection symmetric . based dynamics. In order to improve the deteriorated performance, two new control schemes based on the standard sliding mode technique are proposed. The first sliding control is designed based on a simple ad-hoc model for the asymmetric dynamics, whereas the states are propagated using the exact model developed. It is shown that using this scheme the lost maneuver performance can be reasonably recovered. The second control scheme is formulated using an accurate asymmetric dynamics. This proposed control scheme almost completely recovers the original maneuver performance.