Control of aircraft operating under adverse conditions

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Title: Control of aircraft operating under adverse conditions
Author(s): Salman, Mishah Uzziél
Advisor(s): Chang, Bor-Chin
Keywords: Mechanical Engineering; Airplanes--Control systems; Drone aircraft
Date: 2012-06
Publisher: Drexel University
Thesis: Ph.D., Mechanical Engineering -- Drexel University, 2012
Abstract: Almost all aircraft in use today rely on some form of automatic control system to remain safely aloft. Though control under nominal conditions is a mature eld, control methods are less developed for airborne vehicles operating beyond their nominal ight envelopes. Adversities like loss-of-control and upset conditions a ect all variations of aircraft and are thus of great concern. Two ying vehicles operating under di erent adverse conditions are explored in this study| a spinning gun-launched projectile and a transport aircraft. It is shown that similar closed-loop output-tracking regulation and H2 control methods can be employed to safely control each respective system under dangerous circumstances.For the rst vehicle, a control scheme is proposed that can compensate for the coning angle of a gun launched projectile and allow front-mounted canards to e ciently change the projectile ight path without reaching an aerodynamic stall condition. The problem is formulated as a tracking control problem where the reference signal is a sinusoidal input of non-zero bias. The sinusoidal component directly compensates for the body precession, while the non-zero bias imparts a trajectory-altering control action. This approach enables the canard actuator angles to be e ciently regulated with respect to the vehicle's heading direction to minimize drag and prevent aerodynamic stall.For the second vehicle, a civil transport jet actuator jam failure scenario is explored utilizing the NASA AirSTAR Generic Transport Model (GTM). A control algorithm is developed to mitigate the actuator jam using a recon gurable output-tracking regulator. The regulator is developed using a servomechanism formulation where the failed control surface is modeled as an exogenous input to the degraded plant. The approach exploits a set of linear controllers selectively enabled using switching control and outer-loop compensators to optimally track a desired reference input with the remaining available control surfaces and control authority. This approach addresses the loss-ofcontrol authority over the failed control surface in addition to the persistent disturbance input that arises from the jammed control surface.
URI: http://hdl.handle.net/1860/3812
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