Protocol-Based Conflict Resolution for Air Traffic Control

Abstract

This paper proposes a method for multiple-aircraft conflict avoidance. We assume that aircraft cruise at constant altitude with varying velocities and that conflicts are resolved in the horizontal plane using heading change, velocity change, or a combination thereof. We assume that each aircraft's position, heading, and velocity are available to all aircraft involved in the conflict, we constrain the maneuver to be two straight paths of equal length, and we assume that all aircraft initiate conflict resolution maneuvers at the same time and that once an aircraft has initiated a maneuver, its velocity along the maneuver remains constant. Our multiple-aircraft conflict resolution methodology is presented in two steps; first, we consider an unrealistic but geometrically simple exact conflict, in which the original trajectories of all aircraft collide at a point, in order to derive a closed-form analytic solution for the required heading change, and then we consider a realistic inexact conflict, in which conflict points of multiple aircraft do not coincide. Heading change is a main control input for conflict resolution, yet velocity change is also used for an inexact conflict. We then construct a finite partition of the airspace around the conflict, and using our analytic solution, we derive a protocol for resolving the worst-case conflict within each partition. The result is a multiple-aircraft conflict resolution protocol, or a simple rule which is easily understandable and

Formal Verification of Curved Flight Collision Avoidance Maneuvers: A Case Study

“…1d, which has discontinuities at the entry and exit points of roundabouts, to a fully flyable curved maneuver. Unlike most previously proposed maneuvers [23,2,14,5,4,6,10], FTRM does not have non-flyable instant turns. It is flyable and smoothly curved.…”

“…Hwang et al [10] have presented a straight-line aircraft conflict avoidance maneuver that involves optimization over complicated trigonometric computations, and validate it using random numerical simulation and informal arguments.…”

“…This results in complicated superpositions of physical system dynamics with control, which is an example of a hybrid system [7]. Several numerical [23,11,2,9,10] or optimization-based [11,2,8,10] approaches have been proposed for air traffic control. It is difficult to give sound formal verification results for these approaches due to errors in numerical computations or implicit definition of maneuvers in terms of complicated optimization processes.…”

“…For straight line flight (ω = 0), the movement in space is just linear so that classical analysis techniques can be used [7]. These include pure straight line maneuvers [23,14,5,6,10]; see, e.g., Fig. 1a.…”

“…In air traffic control, collision avoidance maneuvers [23,13,5,6,10] are used to resolve conflicting flight paths that arise during free flight. See Fig.…”