Browsing by Author "Chen, Heming"
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Item Required action time in aircraft conflict resolution.(2010-05) Chen, HemingDue to limitations in their performance capabilities, aircraft must begin avoidance maneuvers well before specified minimum separation standards are reached. In other words, there is a time ahead of a predicted conflict at which aircraft must start to act. This paper presents the concept and a systematic procedure for determining the REquired ACtion Time, or REACT, for pairwise conflict resolutions. REACT marks the least advance time necessary for successful avoidance maneuvers and defines the minimum lookahead window for reliable trajectory predictions. In this paper, the process of conflict detection and resolution is divided into a series of segments, and typical times associated with these segments are estimated. Pairwise conflicts in different encounter geometries are considered. Aircraft flights are described with a dynamic point-mass model that uses position and velocity components as states, and excess thrust, lift, and bank angle as controls. Motion constraints due to both aircraft performance limitations and passenger comfort considerations are imposed. In resolving a potential conflict, it is assumed that one of heading change, altitude change, or speed change is used. Both cooperative and non-cooperative maneuvers are studied. Uncertainties in onboard trajectory state measurements, pilot response delays and behaviors, as well as initial aircraft speeds are represented as random variables. Monte-Carlo numerical simulations are conducted to establish trends of REACTs over different encounter angles for every single control authority. The effectiveness of different control authorities in resolving conflicts are compared.Item A systematic study of terminal area traffic management.(2012-08) Chen, HemingThis dissertation conducts a systematic study of terminal area traffic management using optimization methods. The critical role that the airport plays in national airspace system is introduced. The challenges in managing complex terminal traffic are explained. The necessity and importance of the study is addressed. To assist human air traffic controllers in managing complex terminal traffic, our solution strategy is to calculate each flight's optimal arrival/departure schedule, to minimize the overall flight delay and runway congestion in the entire airport. Three solutions are developed in the thesis, including the static solution, the dynamic solution, and the stochastic solution. The static solution uses one computation and attempts to optimize the schedules of many flights arriving/departing the airport within a wide time window. The accuracy of its solution heavily relies on the quality of the predicted traffic situation acquired right before the computation. On the contrary, the dynamic solution attempts to divide the entire traffic flow into a series of small pieces, and optimize flight schedules piece by piece. It collects the latest traffic information before each computation and experiences far less computational load. Both static and dynamic solutions assume the traffic information to be explicitly known. They are inherently deterministic solutions. The third solution proposed in this thesis is a stochastic solution. It assumes that traffic information is not known with certain due to a variety of random factors in actual flight operations. This stochastic solution is mathematically and structurally designed to handle multiple sources of uncertainties in managing terminal traffic. In the last, the conclusion is given based upon the simulation tests of the three proposed runway scheduling solutions. Future work is also suggested.