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Position validation strategies using partially observable Markov decision processes

Published in:
Proc. 30th IEEE/AIAA Digital Avionics Systems Conference, DASC, 16-20 October 2011, pp. 4A2.

Summary

The collision avoidance system that is currently deployed worldwide relies upon radar beacon surveillance. With its broad deployment over the next decade, aviation surveillance based on Automatic Dependent Surveillance-Broadcast (ADS-B) reports may reduce the need for frequent beacon interrogation over the communication channel, but there is a risk of ADS-B providing erroneous data to the collision avoidance system, resulting in a potential collision. Hence, there is a need to use beacon interrogation to periodically validate ADS-B position reports. Various threshold-based validation strategies based on proximity and closure rate have been suggested to reduce channel congestion while maintaining the reliability of the collision avoidance system. This paper shows how to model the problem of deciding when to validate ADS-B reports as a partially observable Markov decision process, and it explains how to solve for the optimal validation strategy. The effectiveness of this approach is demonstrated in simulation.
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Summary

The collision avoidance system that is currently deployed worldwide relies upon radar beacon surveillance. With its broad deployment over the next decade, aviation surveillance based on Automatic Dependent Surveillance-Broadcast (ADS-B) reports may reduce the need for frequent beacon interrogation over the communication channel, but there is a risk of ADS-B...

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The Tower Flight Data Manager prototype system

Published in:
DASC 2011, 30th IEEE/AIAA Digital Avionics Systems Conference, 16-20 October 2011, pp. 2C5.

Summary

The Tower Flight Data Manager (TFDM) will serve as the next generation air traffic control tower automation platform for surface and local airspace operations. TFDM provides three primary enhancements over current systems: consolidation of diverse data and information sources into a single platform; electronic data exchange, including flight data entries, within and outside the tower cab; and a suite of decision support capabilities leveraging TFDM's access to external data sources and systems. This paper describes a TFDM prototype system that includes integrated surveillance, flight data, and decision support display components. Enhancements in airport configuration management, runway assignment, taxi routing, sequencing and scheduling, and departure route assurance are expected to yield significant benefits in delay reduction, fuel savings, additional capacity, improved access, enhanced safety, and reduced environmental impact. Data are provided on system performance and air traffic controller acceptance from simulation studies and a preliminary field demonstration at Dallas / Ft. Worth International Airport.
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Summary

The Tower Flight Data Manager (TFDM) will serve as the next generation air traffic control tower automation platform for surface and local airspace operations. TFDM provides three primary enhancements over current systems: consolidation of diverse data and information sources into a single platform; electronic data exchange, including flight data entries...

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Analysis of open-loop and closed-loop planning for aircraft collision avoidance

Published in:
2011 14th Int. IEEE Conf. on Intelligent Transportation Systems, 5-7 October 2011, pp. 212-217.

Summary

Open-loop planning has been a popular approach for developing aircraft collision avoidance systems. Open-loop planning computes a future plan to follow without anticipation of how future observations can affect the future course of action. Closed-loop planning, in contrast, takes into account the ability to react to future information. This paper explores trade-offs that exist between the two strategies as they apply to aircraft collision avoidance. It demonstrates some of the performance gains that con be realized by adopting a closed-loop planning strategy.
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Summary

Open-loop planning has been a popular approach for developing aircraft collision avoidance systems. Open-loop planning computes a future plan to follow without anticipation of how future observations can affect the future course of action. Closed-loop planning, in contrast, takes into account the ability to react to future information. This paper...

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Establishing a risk-based separation standard for unmanned aircraft self separation

Published in:
11th AIAA Aviation Technology, Integration, and Operations (ATIO) Conf., 20-22 September 2011.

Summary

Unmanned Aircraft Systems require an ability to sense and avoid other air traffic to gain access to civil airspace and meet requirements in civil aviation regulations. One sense and avoid function is self separation, which requires that aircraft remain well clear. An approach is proposed in this paper to treat well clear as a separation standard, thus posing it as a relative state between aircraft where the risk of collision first reaches an unacceptable level. By this approach, an analytically-derived boundary for well clear can be derived that supports rigorous safety assessment. A preliminary boundary is proposed in both time and distance for the well clear separation standard, and recommendations for future work are made.
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Summary

Unmanned Aircraft Systems require an ability to sense and avoid other air traffic to gain access to civil airspace and meet requirements in civil aviation regulations. One sense and avoid function is self separation, which requires that aircraft remain well clear. An approach is proposed in this paper to treat...

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A field demonstration of the air traffic control Tower Flight Data Manager prototype

Published in:
HFES 2011, Human Factors and Ergonomics Society 55th Annual Mtg., 19-23 September 2011, p. 61-65.

Summary

The development and evaluation process of the Tower Flight Data Manager prototype at Dallas Ft. Worth airport is described. Key results from the first field evaluation are presented, including lessons learned about making electronic flight information acceptable to controllers. Iteration of the field evaluation methods are discussed for practitioner benefit.
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Summary

The development and evaluation process of the Tower Flight Data Manager prototype at Dallas Ft. Worth airport is described. Key results from the first field evaluation are presented, including lessons learned about making electronic flight information acceptable to controllers. Iteration of the field evaluation methods are discussed for practitioner benefit.

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Hazard alerting based on probabilistic models

Published in:
AIAA Modeling and Simulation Technologies Conf., 8-11 August 2011.

Summary

Hazard alerting systems alert operators to potential future undesirable events so that action may be taken to mitigate risk. One way to develop a hazard alerting system based on probabilistic models is by using a threshold-based approach, where the probability of the undesirable event without mitigation is compared against a threshold. Another way to develop such a system is to model the system as a Markov decision process and solve for the hazard alerting strategy that maximizes expected utility. This paper analyzes and compares these two methods. The experiments reveal that an expected utility approach performs better than threshold-based approaches when the dynamic stochasticity is high, where accounting for delays or changes in the alert becomes more important. However, for certain system parameters and operating environments, a threshold-based approach may provide comparable performance.
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Summary

Hazard alerting systems alert operators to potential future undesirable events so that action may be taken to mitigate risk. One way to develop a hazard alerting system based on probabilistic models is by using a threshold-based approach, where the probability of the undesirable event without mitigation is compared against a...

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Accounting for state uncertainty in collision avoidance

Published in:
J. Guidance, Control, and Dynamics, Vol. 34, No. 4, July-August 2011, pp. 951-960.

Summary

An important consideration in the development of aircraft collision avoidance systems is how to account for state uncertainty due to sensor limitations and noise. However, many collision avoidance systems simply use point estimates of the state instead of leveraging the full posterior state distribution. Recently, there has been work on applying decision-theoretic methods to collision avoidance, but the importance of accommodating state uncertainty has not yet been well studied. This paper presents a computationally efficient framework for accounting for state uncertainty based on dynamic programming. Examination of characteristic encounters and Monte Carlo simulations demonstrates that properly handling state uncertainty rather than simply using point estimates can significantly enhance safety and improve robustness to sensor error.
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Summary

An important consideration in the development of aircraft collision avoidance systems is how to account for state uncertainty due to sensor limitations and noise. However, many collision avoidance systems simply use point estimates of the state instead of leveraging the full posterior state distribution. Recently, there has been work on...

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Collision avoidance system optimization with probabilistic pilot response models

Published in:
2011 American Control Conf., 29 June-1 July 2011, pp. 2765-2770.

Summary

All large transport aircraft are required to be equipped with a collision avoidance system that instructs pilots how to maneuver to avoid collision with other aircraft. Uncertainty in the compliance of pilots to advisories makes designing collision avoidance logic challenging. Prior work has investigated formulating the problem as a Markov decision process and solving for the optimal collision avoidance strategy using dynamic programming. The logic was optimized to a pilot response model in which the pilot responds deterministically to all alerts. Deviation from this model during flight can degrade safety. This paper extends the methodology to include probabilistic pilot response models that capture the variability in pilot behavior in order to enhance robustness.
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Summary

All large transport aircraft are required to be equipped with a collision avoidance system that instructs pilots how to maneuver to avoid collision with other aircraft. Uncertainty in the compliance of pilots to advisories makes designing collision avoidance logic challenging. Prior work has investigated formulating the problem as a Markov...

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Unmanned aircraft collision avoidance using continuous-state POMDPs

Published in:
2011 Robotics: Science and Systems, 27-30 June 2011.

Summary

An effective collision avoidance system for unmanned aircraft will enable them to fly in civil airspace and greatly expand their applications. One promising approach is to model aircraft collision avoidance as a partially observable Markov decision process (POMDP) and automatically generate the threat resolution logic for the collision avoidance system by solving the POMDP model. However, existing discrete-state POMDP algorithms cannot cope with the high-dimensional state space in collision avoidance POMDPs. Using a recently developed algorithm called Monte Carlo Value Iteration (MCVI), we constructed several continuous-state POMDP models and solved them directly, without discretizing the state space. Simulation results show that our 3-D continuous-state models reduce the collision risk by up to 70 times, compared with earlier 2-D discrete-state POMDP models. The success demonstrates both the benefits of continuous-state POMDP models for collision avoidance systems and the latest algorithmic progress in solving these complex models.
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Summary

An effective collision avoidance system for unmanned aircraft will enable them to fly in civil airspace and greatly expand their applications. One promising approach is to model aircraft collision avoidance as a partially observable Markov decision process (POMDP) and automatically generate the threat resolution logic for the collision avoidance system...

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Analytical workload model for estimating en route sector capacity in convective weather

Published in:
9th USA/Europe Air Traffic Management Research and Development Sem., ATM 2011, 14-17 June 2011.

Summary

We have extended an analytical workload model for estimating en route sector capacity to include the impact of convective weather. We use historical weather avoidance data to characterize weather blockage, which affects the sector workload in three ways: (1) Increase in the conflict resolution task rate via reduction in available airspace, (2) increase in the recurring task load through the rerouting of aircraft around weather, and (3) increase in the inter-sector coordination rate via reduction in the mean sector transit time. Application of the extended model to observed and forecast data shows promise for future use in network flow models.
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Summary

We have extended an analytical workload model for estimating en route sector capacity to include the impact of convective weather. We use historical weather avoidance data to characterize weather blockage, which affects the sector workload in three ways: (1) Increase in the conflict resolution task rate via reduction in available...

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