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