Algorithm Design for Crossing and Passing Applications

1. Algorithm Design for Crossing and Passing ApplicationsJohn Anderson and Colin GoodchildUniversity of Glasgow, UKThierry MiquelDSNA, Toulouse, FranceASAS-TN2 2nd WorkshopRome 3-5 April 2006

2. 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

3. 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-TN2 2nd Workshop, Rome 3-5 April 2006

4. Co-altitude Applications Turning Point Route Offset Route ASAS-TN2 2nd Workshop, Rome 3-5 April 2006

5. Climb/Descent Applications ASAS-TN2 2nd Workshop, Rome 3-5 April 2006

6. Generic Features of ASAS C&P Applications ASAS-TN2 2nd Workshop, Rome 3-5 April 2006

7. 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

8. ASAS C&P Operational Phases Controller Set-up Phase Flight Crew Identification Phase Clearance Phase Execution Phase Termination Phase ASAS-TN2 2nd Workshop, Rome 3-5 April 2006

9. ASAS Airborne Operational Logic not_feasible clearance_issued conflict ATCo responsible for separation test resolution feasibility Abort phase test conflict feasible no_conflict no_commit update resolution manoeuvre conformance commit review delegation continue_delegation no_separation test lateral separation execute resolution manoeuvre separation return_delegation Clearance no_deviation Termination not_clear test clear of traffic test deviation non_conformance resume own navigation clear deviation clear_of_traffic_acknowledged Execution ASAS-TN2 2nd Workshop, Rome 3-5 April 2006

10. ASAS Resolution Implementation • Resolution control: • Point based (FMS) • Velocity based (Autopilot) ASAS-TN2 2nd Workshop, Rome 3-5 April 2006

11. ASAS Data Sources Target ID ASAS application type ASAS manoeuvre class Flight plan ASAS resolution controls ADS-B messages from other aircraft ASAS algorithms Ownship navigation data and dynamics ASAS performance metrics Aircraft performance Wind ASAS-TN2 2nd Workshop, Rome 3-5 April 2006

12. 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

13. 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

14. ASAS Manoeuvre Parameterisation I • Resolution manoeuvre parameterised by: • heading change α (discrete values) • heading change start time t0 • heading change end time t1 ASAS-TN2 2nd Workshop, Rome 3-5 April 2006

15. S - Straight Line Segment T – Constant Radius Turn Segment ASAS Manoeuvre Parameterisation II • Resolution manoeuvre parameterised by (Vilaplana (2002)): • discrete mode sequence and switch times ASAS-TN2 2nd Workshop, Rome 3-5 April 2006

16. 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

17. 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 • Maximise safety ASAS-TN2 2nd Workshop, Rome 3-5 April 2006

18. Features of Robust Resolution Cost Function Infeasible Feasible Robust Variation Infeasible Optimal Feasible Environmental Parameters ASAS-TN2 2nd Workshop, Rome 3-5 April 2006

19. 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. ASAS-TN2 2nd Workshop, Rome 3-5 April 2006

20. Planned Activities and Deliverables ASAS-TN2 2nd Workshop, Rome 3-5 April 2006