Protocol-based Conflict Resolution

This paper proposes a method for multiple-aircraft conﬂict avoidance.

Assumptions

aircraft cruise at constant altitude with varying velocities.
conﬂicts are resolved in the horizontal plane using heading change, velocity change, or a combination thereof.
each aircraft’s position, heading, and velocity are available to all aircraft involved in the conﬂict.
the maneuver is constrained to be two straight paths of equal length.
all aircraft initiate conﬂict resolution maneuvers at the same time.
once an aircraft has initiated a maneuver, its velocity along the maneuver remains constant.

Methodology

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 implementable by all aircraft involved in the conﬂict, and which provides guarantees of safety.
We show that this solution is robust to uncertainties in the aircraft’s position, heading, and velocity, as well as to path smoothing, and asynchronous maneuvers.
We present simulation results for a dynamic aircraft model for various multiple aircraft conﬂict scenarios.

Related Publication

I. Hwang, J. Kim, and C. Tomlin, “Protocol-Based Conflict Resolution for Air Traffic Control,” Air Traffic Control Quarterly, Vol. 15(1), 2007