Publications

Refine Results

(Filters Applied) Clear All

Collision avoidance for general aviation

October 16, 2011
  |
Conference Paper
Author:
Thomas B. Billingsley
…
Published in:
30th AIAA/IEEE Digital Avionics Systems Conf., 16-20 October 2011.
Topic:
collision avoidance
R&D area:
R&D group:

Summary

The Traffic Alert and Collision Avoidance System (TCAS) is mandated on all large transport aircraft to reduce mid-air collision risk. Since its introduction, no mid-air collisions between TCAS-equipped aircraft have occurred in the United States. However, General Aviation (GA) aircraft are generally not equipped with TCAS and experience collisions several times per year. There is interest in low-cost collision avoidance systems for GA aircraft to reduce collision risk with other GA aircraft as well as with TCAS-equipped aircraft. Since TCAS was designed for large aircraft that can achieve greater vertical rates, the assumptions made by the system and the associated advisories are not always appropriate for GA aircraft. Modifying the TCAS logic to accommodate GA aircraft is far from straightforward. Even minor changes to TCAS to correct operational issues are difficult to implement due to the interaction of the complex rules defining the logic. Recent work has explored an alternative to the TCAS logic based on optimization with respect to a probabilistic model of aircraft behavior. The model encodes performance constraints of GA aircraft, and a computational technique called dynamic programming allows the optimal collision avoidance strategy to be computed efficiently. Prior work has focused on systems that meet the performance assumptions of the existing TCAS logic. However, these assumptions are not always appropriate for GA aircraft. This paper will present simulation results comparing the existing logic to logic that has been optimized to operate onboard GA aircraft. If both aircraft are equipped with collision avoidance logic, it is important that the advisories be coordinated to prevent both aircraft from climbing or descending. The TCAS logic has a built-in coordination mechanism with which a GA system must maintain compatibility. Several coordination strategies, both with the optimized logic and the current logic, are evaluated in simulation.
READ LESS

Summary

The Traffic Alert and Collision Avoidance System (TCAS) is mandated on all large transport aircraft to reduce mid-air collision risk. Since its introduction, no mid-air collisions between TCAS-equipped aircraft have occurred in the United States. However, General Aviation (GA) aircraft are generally not equipped with TCAS and experience collisions several...

READ MORE
Collision avoidance for general aviation

Estimating the likelihood of success in departure management strategies during convective weather

October 16, 2011
  |
Conference Paper
Author:
Richard A. DeLaura
…
Published in:
Proc. 30th IEEE/AIAA Digital Avionics Systems Conference, DASC, 16-20 October 2011, pp. 6D4.
Topic:
aviation weather
R&D area:
R&D group:

Summary

The presence of convective weather (thunderstorms) in terminal and nearby en route airspace of major metroplex areas can have significant impacts on departure operations. Traffic on departure routes impacted by convective weather may be constrained by miles-in-trail (MIT) restrictions, to allow controllers the time needed to maneuver individual flights around thunderstorms that pilots wish to avoid. When the workload required to manage traffic flows becomes too great, departure routes may be closed. Departures still on the ground that are filed on closed or restricted routes may face significant delays as they wait for clearance on their filed route, or for a viable reroute to be implemented. The solution proposed in concepts such as the Integrated Departure Route Planning tool (IDRP) [1] is the use of weather and departure demand forecasts to plan and implement reroutes to avoid weather and volume congestion proactively, well in advance of route restrictions or closures.
READ LESS

Summary

The presence of convective weather (thunderstorms) in terminal and nearby en route airspace of major metroplex areas can have significant impacts on departure operations. Traffic on departure routes impacted by convective weather may be constrained by miles-in-trail (MIT) restrictions, to allow controllers the time needed to maneuver individual flights around...

READ MORE
Estimating the likelihood of success in departure management strategies during convective weather

Initial validation of a convective weather avoidance model (CWAM) in departure airspace

October 16, 2011
  |
Conference Paper
Author:
Mikhail Rubnich
…
Published in:
DASC 2011, 30th IEEE/AIAA Digital Avionics Systems Conference, 16-20 October 2011, pp. 3A2.
Topic:
aviation weather
R&D area:
R&D group:

Summary

The Convective Weather Avoidance Model (CWAM) translates gridded, deterministic weather observations and forecasts into Weather Avoidance Fields (WAF). The WAF gives the probability, at each point in the grid, that a pilot will choose to deviate around convective weather at that location. CWAM have been developed and validated for en route, high altitude, level flight, low altitude level flight, and for descending arrivals. A heuristic CWAM for departures was also developed and deployed as part of the Route Availability Planning Tool (RAPT) prototype development in New York and Chicago. This paper presents an evaluation of the departure CWAM that is currently deployed as part of RAPT, based on an analysis of departure traffic in the Chicago terminal area during convective weather events.
READ LESS

Summary

The Convective Weather Avoidance Model (CWAM) translates gridded, deterministic weather observations and forecasts into Weather Avoidance Fields (WAF). The WAF gives the probability, at each point in the grid, that a pilot will choose to deviate around convective weather at that location. CWAM have been developed and validated for en...

READ MORE
Initial validation of a convective weather avoidance model (CWAM) in departure airspace

Position validation strategies using partially observable Markov decision processes

October 16, 2011
  |
Conference Paper
Author:
Mykel J. Kochenderfer
…
Published in:
Proc. 30th IEEE/AIAA Digital Avionics Systems Conference, DASC, 16-20 October 2011, pp. 4A2.
Topic:
air traffic control
R&D area:
R&D group:

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.
READ LESS

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...

READ MORE
Position validation strategies using partially observable Markov decision processes

The Tower Flight Data Manager prototype system

October 16, 2011
  |
Conference Paper
Author:
Vineet Mehta
…
Published in:
DASC 2011, 30th IEEE/AIAA Digital Avionics Systems Conference, 16-20 October 2011, pp. 2C5.
Topic:
air traffic control
R&D area:
R&D group:

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.
READ LESS

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...

READ MORE
The Tower Flight Data Manager prototype system

Compact external-cavity semiconductor mode-locked laser with quantum-well-intermixed modulator and saturable absorber

October 9, 2011
  |
Conference Paper
Author:
Jason J. Plant
…
Published in:
IPC11, IEEE Photonics Conf., 9-13 October 2011, pp. 753-754.
Topic:
photonics
R&D area:
R&D group:

Summary

We demonstrate a slab-coupled optical waveguide external-cavity mode-locked laser having unique bandedges for the amplifier, modulator and saturable absorber elements. An average output power of 50mW and timing jitter of 254fs is achieved at 1.5-GHz.
READ LESS

Summary

We demonstrate a slab-coupled optical waveguide external-cavity mode-locked laser having unique bandedges for the amplifier, modulator and saturable absorber elements. An average output power of 50mW and timing jitter of 254fs is achieved at 1.5-GHz.

READ MORE
Compact external-cavity semiconductor mode-locked laser with quantum-well-intermixed modulator and saturable absorber

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

October 5, 2011
  |
Conference Paper
Author:
James P. Chryssanthacopoulos
…
Published in:
2011 14th Int. IEEE Conf. on Intelligent Transportation Systems, 5-7 October 2011, pp. 212-217.
Topic:
collision avoidance
R&D area:
R&D group:

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.
READ LESS

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...

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

SOI circuits powered by embedded solar cell

October 3, 2011
  |
Journal Article
Author:
Chang-Lee Chen
…
Published in:
2011 IEEE SOI Conf., 3-6 October 2011.
Topic:
microelectronics
R&D area:

Summary

Solar cells embedded in the SOI substrate were successfully used as the sole energy source to power a ring oscillator fabricated using an ultra-low-power fully depleted SOI process on the same wafer. The speed of the ring oscillator increased with increasing light intensity and showed a fastest oscillation with a 4.5 ns stage delay and 0.26 fJ power-delay product. The maximum power generated by the solar cell was 9.6 mW/cm2 with an efficiency of 11.6%.
READ LESS

Summary

Solar cells embedded in the SOI substrate were successfully used as the sole energy source to power a ring oscillator fabricated using an ultra-low-power fully depleted SOI process on the same wafer. The speed of the ring oscillator increased with increasing light intensity and showed a fastest oscillation with a...

READ MORE
SOI circuits powered by embedded solar cell

Dual polarization radar winter storm studies supporting development of NEXRAD-based aviation hazard products

September 29, 2011
  |
Conference Paper
Author:
Earle R. Williams
…
Published in:
35th Conf. on Radar Meteorology, 26-30 September 2011.
Topic:
aviation weather
R&D area:
R&D group:

Summary

The Next Generation Weather Radar (NEXRAD) dual polarization upgrade has begun adding a functional enhancement to classify hydrometeors. MIT Lincoln Laboratory (LL) develops NEXRAD-based weather radar products for Federal Aviation Administration (FAA) weather systems such as Corridor Integrated Weather System (CIWS), Integrated Terminal Weather System (ITWS), and Weather and Radar Processor (WARP). Without dual polarization, those products are limited to providing information on precipitation location and intensity. With dual polarization, LL is now developing new aviation weather products to determine locations of hydrometeor-based hazards. A product for Icing Hazards Level (IHL) is expected to benefit the FAA. LL has partnered with Valparaiso University (VU) in northern Indiana near Chicago since 2008 to study the evolution of winter storms prior to the NEXRAD dual polarization upgrade. VU contributes to the study a C-band dual polarization weather radar, an on-demand local sounding capability, and a surface winter weather verification team. Additionally, the Wolcott, IN wind profiler is about 70 km south within viewing range of the VU radar, and provides information on the fall speeds of the hydrometeors of interest. This resource-rich location has allowed for substantive study of many winter storm types: synoptic, lake effect, and frontal passages. A key to development of the IHL product is the ability to interpret dual polarization radar signatures from the winter microphysical states and precipitation structures. Evolution of the structures is a response to the microphysical water and ice saturation (sub or super) states. The magnitude of the vertical lift may affect the saturation states. Methods to segregate the radar signatures will be important regarding the inferred presence of a supercooled water icing hazard. The blizzard of Feb. 1 and 2, 2011 produced four distinct precipitation periods (snow, sleet, freezing drizzle, and lake effect snow), all of which will be discussed. The paper and presentation will also detail findings from the study of multiple winter storms and how they inform the development of the IHL product.
READ LESS

Summary

The Next Generation Weather Radar (NEXRAD) dual polarization upgrade has begun adding a functional enhancement to classify hydrometeors. MIT Lincoln Laboratory (LL) develops NEXRAD-based weather radar products for Federal Aviation Administration (FAA) weather systems such as Corridor Integrated Weather System (CIWS), Integrated Terminal Weather System (ITWS), and Weather and Radar...

READ MORE
Dual polarization radar winter storm studies supporting development of NEXRAD-based aviation hazard products

On-chip nonlinear digital compensation for RF receiver

September 21, 2011
  |
Conference Paper
Author:
Karen M. Gonzalez-Valentin Gettings
…
Published in:
HPEC 2011: Conf. on High Performance Embedded Computing, 21-22 September 2011.
Topic:
signal processing
R&D area:
R&D group:

Summary

A system-on-chip (SOC) implementation is an attractive solution for size, weight and power (SWaP) restricted applications, such as mobile devices and UAVs. This is partly because the individual parts of the system can be designed for a specific application rather than for a broad range of them, like commercial parts usually must be. Co-design of the analog hardware and digital processing further enhances the benefits of SOC implementations by allowing, for example, nonlinear digital equalization to further enhance the dynamic range of a given front-end component. This paper presents the implementation of nonlinear digital compensation for an active anti-aliasing filter, which is part of a low-power homodyne receiver design. The RF front-end circuitry and the digital compensation will be integrated in the same chip. Co-design allows the front-end to be designed with known dynamic range limitations that will later be compensated by nonlinear equalization. It also allows nonlinear digital compensation architectures matched to specific circuits and dynamic range requirements--while still maintaining some flexibility to deal with process variation--as opposed to higher power general purpose designs.
READ LESS

Summary

A system-on-chip (SOC) implementation is an attractive solution for size, weight and power (SWaP) restricted applications, such as mobile devices and UAVs. This is partly because the individual parts of the system can be designed for a specific application rather than for a broad range of them, like commercial parts...

READ MORE
On-chip nonlinear digital compensation for RF receiver
891-900 of 2318