The conflict prediction and resolution capability resident in the Center/TRACON Automation System (CTAS) has been enhanced and field tested. All-track processing (overflights, arrivals, departures), conflict probability estimation, and interactive trial planning, were incorporated into the Conflict Prediction and Trial Planning (CPTP) tool for field test evaluation. The objective of the work was to field test CPTP under operational air traffic control conditions and to measure benefits of CPTP capability to air traffic controllers and airspace users. The system was tested on the operational floor at the Denver Air Route Traffic Control Center in September 1997. It was found that controllers using CPTP-aiding resolved many conflicts by issuing a direct-route clearance to one of the aircraft. A direct route often resolved a conflict well before it became tactical, gave the aircraft a shortcut , and required one less controller clearance. The potential for a threefold increase in direct routing was noted with CPTP-aiding over baseline operations with no aiding. The data show better than a twofold increase in the number of direct-route clearances actually issued to aircraft when controllers were using the CPTP system. The ability of CPTP to confirm that a trial trajectory resolves the conflict without creating any other conflicts was consistently identified by the controllers as one of its most powerful features.
Direction cosines and quaternions are useful for representing rigid-body attitude because they exhibit no kinematic singularities. Each utilizes more variables than the minimum three degrees of freedom required to specify attitude. Therefore, application of a nonlinear inversion procedure to either formulation introduces singularities. Furthermore, in designing an attitude-control system, it is not appropriate to express attitude error as a difference of direction cosines (or quaternions). One should employ a measure of attitude error that not only is minimal but preserves orthogonal rotation properties as well. This note applies an inversion procedure to an appropriate measure of attitude error, so that the singularity occurs when the error reaches f 180". This approach leads to the realization of a new model-follower attitude-control system that exhibits exact linear attitude-error dynamics.
This paper describes simulation and field test evaluation of an integrated decision support tool for trial planning and arrival metering in transition airspace, i.e., en route airspace near the terminal area. The challenge for this tool will be to solve tactical arrival-metering problems. The tool calculates fuelefficient descent trajectories, arrival sequencing and metering, and includes a trial-planning function for conflict resolution. Simulation evaluations were conducted at NASA Ames in April and July of 1998 and field-test evaluation was conducted at Fort Worth Center in November 1998. Results indicate the trialplanning function provided benefits for strategic conflict resolution but controllers preferred not to use it in the more tactical arrival-metering environment. Controllers often used the trial planner to determine if a direct route to a downstream fix along the aircraft's route of flight was feasible. The test also confirmed the high controller acceptance of the trial-planning capability.
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