Browsing by Author "Dabney, James Bruster"

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    Autonomous robotic crawler for in-pipe inspection
    (2007-02-27) Ghorbel, Fathi Hassan; Dabney, James Bruster; Rice University; University of Houston Clear Lake; United States Patent and Trademark Office
    The specification discloses a robot for inspection adapted to travel virtually unlimited distances through small-diameter enclosed spaces such as conduits or ducts, preferably using a fluid-driven screw-drive propulsion system. The robot preferably includes a plurality of wheels inclined at an angle greater than zero degrees and less than ninety degrees to the longitudinal axis of the pipe, a plurality of wheels aligned parallel to the longitudinal axis of the pipe, and a power system for causing relative rotation of the sections bearing the pitched and non-pitched wheels. The robot may include internal fluid flow passages, notched wheels, multiple retractable wheels, and is configured so as to have an operating diameter less than six and preferably less than two inches.
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    Optimal combat maneuvers of a next-generation jet fighter aircraft
    (1998) Dabney, James Bruster; Miele, Angelo
    This thesis deals with the optimization of four classes of combat maneuvers for a next-generation jet fighter aircraft: climb maneuvers, fly-to-point maneuvers, pop-up attack maneuvers, and dive recovery maneuvers. For the first three classes of maneuvers, the optimization criterion is the minimization of the flight time, resulting in a Mayer-Bolza problem of optimal control; for the fourth class, the optimization criterion is the minimization of the maximum altitude loss during dive recovery, resulting in a Chebyshev problem of optimal control. Each class of problems is solved using the sequential gradient-restoration algorithm for optimal control. Among the four classes of combat maneuvers studied, only dive recovery benefits from the ability of a next-generation fighter aircraft to maneuver at extremely high angles of attack. For the other three classes, relatively low angles of attack are required. The optimal climb trajectories are characterized by three distinct segments: a central segment often flown with a load factor of nearly 1 and two terminal segments (dive or zoom) to and from the central segment. The central and final segments are nearly independent of the initial conditions, instead being dominated by the final conditions. The optimal fly-to-point trajectories consist of three segments: turning, characterized by relatively high load factor; level acceleration at maximum thrust; and finally, resumption of steady-state cruising. The effects of the heading change magnitude and the load factor limit are discussed. The optimal pop-up trajectories consist of three segments flown at maximum power: pitch-up, zoom, and pitch-down. The effects of using the afterburner, heading change magnitude, and dive angle magnitude are discussed. The optimal dive recovery trajectories consist of one to three segments, depending on initial speed and flight path angle. All the optimal trajectories conclude with a pitch-up at the maximum available load factor. For very low initial speed, the pitch-up is preceded by a brief supermaneuver segment. For very low initial speed coupled with very high initial flight path angle, the supermaneuver segment is preceded by a dive initiation segment. The optimal trajectories reported here serve two purposes. First, they can benefit aircraft designers by highlighting those flight characteristics that are most beneficial in combat. Second, they can benefit aircraft pilots as the basis for guidance trajectories that approximate the optimal trajectories.