CONFLICT DETECTION AND RESOLUTION IN THE PRESENCE OF PREDICTION ERROR

Heinz Erzberger, Russell A. Paielli, Douglas R. Isaacson, and Michelle M. Eshow


Abstract

This paper describes the design of a conflict detection and resolution tool,
referred to as a Conflict Probe, for use by enroute (Center) air traffic 
controllers.  This tool is designed to help detect and resolve all classes 
of conflicts, such as overflight/ overflight, arrival/ overflight,
climbout/ overflight, etc., up to twenty minutes in advance.  The  design
is based on an approach that combines deterministic trajectory prediction 
and stochastic conflict analysis to achieve reliable conflict detection.  
The paper begins by formulating error models for trajectory prediction.  
Then an efficient algorithm is described for estimating conflict probability
as a function of encounter geometry.  The conflict probability theory and 
algorithm are applied to the design of the Conflict Probe and are further 
used to develop a method of automated conflict resolution with constraints
on the post-resolution conflict probability.  Next, aircraft performance 
models and equations of motion for generating four-dimensional trajectories
are presented.  The paper concludes with a description of the methods used 
to minimize the time to search the trajectories for potential conflicts. 
Performance tests of the search algorithm indicate that up to 800 aircraft
can be processed by the Probe within a search cycle of 10 seconds.  The
Conflict Probe has been implemented as a software process within the Center-
TRACON Automation System (CTAS).  It uses the trajectory synthesis capability
of CTAS to generate predicted trajectories for the conflict search and trial
resolution processes.  Field evaluation of the Probe will be conducted at 
the Denver and Fort Worth Centers beginning in September 1997.