Algorithm Design for Crossing and Passing
Applications
John Anderson and Colin Goodchild
University of Glasgow, UK
Thierry Miquel
DSNA, Toulouse, France
ASAS-TN2 2nd Workshop
Rome 3-5 April 2006
Contents
 Description of selected ASAS C&P applications
– ASAS manoeuvre types
– ASAS airborne operational logic
– ASAS implementation and data sources
 Synthesis of ASAS resolution manoeuvres
– Approaches to conflict detection and resolution
– Sources of uncertainty
– Robust ASAS manoeuvres
 Current status and planned activities
ASAS-TN2 2nd Workshop, Rome 3-5 April 2006
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ASAS C&P Applications in Radar Airspace
 Selective C&P applications and operational procedures in radar
airspace are defined in deliverables D1.1 and D1.3:
ASAS C&P Application
ASAS Manoeuvre Class
 Co-altitude pass behind
 Turning point route
 Co-aItitude pass in-front
 Offset route
 Climbing pass behind
 Descending pass behind
ASAS-TN2 2nd Workshop, Rome 3-5 April 2006
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Co-altitude Applications
Suggested TCPs
Suggested TCP
Clear of
Traffic Point
Clearance aircraft
Target aircraft
Turning Point Route
Clear of
Traffic Point
Clearance aircraft
Target aircraft
Offset Route
ASAS-TN2 2nd Workshop, Rome 3-5 April 2006
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Climb/Descent Applications
Vertical Profile
Target aircraft
A3
19
A3
19
Clearance aircraft
Offset Route
Turning Point Route
Clear of
Traffic Point
Clear of
Traffic Point
Suggested TCP
Clearance aircraft
Target aircraft
Suggested TCP
Suggested TCP
Clearance aircraft
ASAS-TN2 2nd Workshop, Rome 3-5 April 2006
Target aircraft
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Generic Features of ASAS C&P Applications
Sector
boundaries
XTKmax
Target aircraft
Limit for end
of delegation
Maximum track
alteration
Clearance
aircraft
Surrounding
traffic
TKmax
: published way point
ASAS-TN2 2nd Workshop, Rome 3-5 April 2006
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Generic Features of ASAS C&P Applications
 Finite time-horizon (lookahead time 5-10 minutes)
 Fixed topology manoeuvre classes
 Manoeuvre envelope constraints
 Lateral manoeuvre requirement only
 A priori specification of resolution manoeuvres via FMS/Autopilot
with scope for limited adaptation following initiation of manoeuvre
 Third-party aircraft assumed isolated from ASAS designated pair
ASAS-TN2 2nd Workshop, Rome 3-5 April 2006
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ASAS C&P Operational Phases
Set-up
Phase
Controller
Flight Crew
Identification
Phase
Clearance
Phase
Execution
Phase
Termination
Phase
ASAS-TN2 2nd Workshop, Rome 3-5 April 2006
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ASAS Airborne Operational Logic
clearance_issued
not_feasible
conflict
ATCo responsible for separation
test
resolution
feasibility
test
conflict
Abort phase
feasible
no_conflict
no_commit
review
continue_delegation
delegation
update
resolution
manoeuvre
conformance
no_separation
execute
resolution
manoeuvre
return_delegation
Clearance
commit
no_deviation
test
deviation
test
lateral
separation
not_clear
non_conformance
separation
Termination
test
clear of
traffic
clear
deviation
Execution
resume
own
navigation
clear_of_traffic_acknowledged
ASAS-TN2 2nd Workshop, Rome 3-5 April 2006
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ASAS Resolution Implementation
 Resolution control:
– Point based (FMS)
– Velocity based (Autopilot)
Navigation
Control Parameters
FMS
2D TCP’s
Autopilot
TV’s (Speed, Heading)
ASAS-TN2 2nd Workshop, Rome 3-5 April 2006
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ASAS Data Sources
Target ID
ASAS application type
ASAS manoeuvre class
ADS-B messages
from other aircraft
Flight plan
ASAS resolution
controls
ASAS algorithms
Ownship navigation
data and dynamics
ASAS performance
metrics
Wind
Aircraft performance
ASAS-TN2 2nd Workshop, Rome 3-5 April 2006
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ASAS C&P Conflict Resolution Problem
Given:
 the initial/current conflict geometry and broadcast aircraft states
 the clearance aircraft performance and manoeuvre envelope
 a time-horizon dependent on the manoeuvre envelope
Find:
 the ‘best’ nominal resolution manoeuvre compliant with the required
separation criterion, acceptable deviation constraints and
acceptable level of operational performance.
‘Best’ = Safe + Efficient + Robust
ASAS-TN2 2nd Workshop, Rome 3-5 April 2006
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Synthesis of ASAS Resolution Manoeuvres
 Conflict resolution algorithms (state-based)
– Geometric (NLR/NASA FreeFlight, MA-AFAS, INTENT, MFF, DAG-TM)
– Graph-based search
– Simulation-based optimisation (HYBRIDGE)
 Nominal trajectory models
– Piecewise-linear (constant velocity) segments
– Physical trajectory segments (eg co-ordinated turn segments,
constant Mach/CAS segments)
 Uncertainty models/Conflict metrics
– Nominal/Minimum separation
– Worst-case/Minimum separation of extremal bound
– Probabilistic/Probability of conflict
ASAS-TN2 2nd Workshop, Rome 3-5 April 2006
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ASAS Manoeuvre Parameterisation I
 Resolution manoeuvre parameterised by:
– heading change α (discrete values)
– heading change start time t0
– heading change end time t1

t0
t1
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ASAS Manoeuvre Parameterisation II
 Resolution manoeuvre parameterised by (Vilaplana (2002)):
– discrete mode sequence and switch times
S
T
T
S
T
S
S
S - Straight Line Segment
T – Constant Radius Turn Segment
ASAS-TN2 2nd Workshop, Rome 3-5 April 2006
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Sources of Uncertainty
 Trajectory prediction errors resulting from:
– Flight mode errors/uncertainty in climb/descent
– Wind and (vertical) wind gradient uncertainty
– Aircraft performance errors
– Aircraft weight errors
– Aircraft turn dynamics omission
– Flight crew response latency
– (Post-COT) intent errors
– ADS-B failures and data anomalies
ASAS-TN2 2nd Workshop, Rome 3-5 April 2006
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Robust Resolution Manoeuvres
 Robustness to uncertainty in environmental parameters and
processes
– Attempt to design ‘tolerance’ to uncertain environmental
parameters in ASAS resolution manoeuvres while satisfying
safety and efficiency criteria.
– Minimise ‘false alarms’ and unnecessary manoeuvres
PUA (t )  0
– Maximise safety
PSA (t )  1
ASAS-TN2 2nd Workshop, Rome 3-5 April 2006
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Features of Robust Resolution
Cost Function
Infeasible
Feasible
Robust
Variation
Optimal
Infeasible
Feasible
Environmental Parameters
ASAS-TN2 2nd Workshop, Rome 3-5 April 2006
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Candidate ASAS CR Algorithms
 Geometric and graph-based search methods fulfil the dual
requirements of simplicity and transparancy in the real-time
synthesis of ASAS resolution manoeuvres.
 The additional requirement of robustness to uncertainties in
environmental and flight mode parameters can be incorporated
implicitly in a search-based approach to resolution synthesis.
 Both geometric and search-based resolution methods offer scope
for limited real-time adaptation of the ASAS manoeuvre.
 Search-based resolution methods can be modified to accommodate
trajectory segment models in both co-altitude and climb/descent
applications.
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Planned Activities and Deliverables
Activity
Deliverable
Planned Date
Survey of candidate CD&R
processes and algortihms. (UoG)
D2.1
23/12/05
Implementation of geometric and
graph-based search methods in
ASAS test-bed. (DSNA/UoG)
D2.2
12/01/07
Development of the ‘robust’
manoeuvre concept (with particular
emphasis on climb/ descent
applications). (UoG)
D2.3
12/01/07
Preparation of algorithms for
advanced simulation. (DSNA/UoG)
D2.4
09/03/07
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