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  • 1
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    Pd and Ag metal-silicate partitioning applied to Earth differentiation and core-mantle exchange (2011)
    Wiley
    Details
    Publication Date: 2011-01-18
    Print ISSN: 1086-9379
    Electronic ISSN: 1945-5100
    Topics: Geosciences , Physics
    Published by Wiley
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    PAPER CURRENT
  • 2
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    Robust Maneuvering Envelope Estimation Based on Reachability Analysis in an Optimal Control Formulation (2013)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This paper discusses an algorithm for estimating the safe maneuvering envelope of damaged aircraft. The algorithm performs a robust reachability analysis through an optimal control formulation while making use of time scale separation and taking into account uncertainties in the aerodynamic derivatives. Starting with an optimal control formulation, the optimization problem can be rewritten as a Hamilton- Jacobi-Bellman equation. This equation can be solved by level set methods. This approach has been applied on an aircraft example involving structural airframe damage. Monte Carlo validation tests have confirmed that this approach is successful in estimating the safe maneuvering envelope for damaged aircraft.
    Keywords: Aircraft Stability and Control; Air Transportation and Safety
    Type: ARC-E-DAA-TN11112 , International Conference on Control and Fault-Tolerant Systems (SysTol''13); Oct 09, 2013 - Oct 11, 2013; Nice; France
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Safe Maneuvering Envelope Estimation Based on a Physical Approach (2013)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This paper discusses a computationally efficient algorithm for estimating the safe maneuvering envelope of damaged aircraft. The algorithm performs a robust reachability analysis through an optimal control formulation while making use of time scale separation and taking into account uncertainties in the aerodynamic derivatives. This approach differs from others since it is physically inspired. This more transparent approach allows interpreting data in each step, and it is assumed that these physical models based upon flight dynamics theory will therefore facilitate certification for future real life applications.
    Keywords: Air Transportation and Safety; Aircraft Stability and Control
    Type: ARC-E-DAA-TN10295 , AIAA Guidance, Navigation, and Control Conference 2013; Aug 18, 2013 - Aug 22, 2013; Boston, MA; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    A Survey of Health Management User Objectives Related to Diagnostic and Prognostic Metrics (2010)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: One of the most prominent technical challenges to effective deployment of health management systems is the vast difference in user objectives with respect to engineering development. In this paper, a detailed survey on the objectives of different users of health management systems is presented. These user objectives are then mapped to the metrics typically encountered in the development and testing of two main systems health management functions: diagnosis and prognosis. Using this mapping, the gaps between user goals and the metrics associated with diagnostics and prognostics are identified and presented with a collection of lessons learned from previous studies that include both industrial and military aerospace applications.
    Keywords: Systems Analysis and Operations Research
    Type: ARC-E-DAA-TN789
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    Shielded-Twisted-Pair Cable Model for Chafe Fault Detection via Time-Domain Reflectometry (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: This report details the development, verification, and validation of an innovative physics-based model of electrical signal propagation through shielded-twisted-pair cable, which is commonly found on aircraft and offers an ideal proving ground for detection of small holes in a shield well before catastrophic damage occurs. The accuracy of this model is verified through numerical electromagnetic simulations using a commercially available software tool. The model is shown to be representative of more realistic (analytically intractable) cable configurations as well. A probabilistic framework is developed for validating the model accuracy with reflectometry data obtained from real aircraft-grade cables chafed in the laboratory.
    Keywords: Air Transportation and Safety
    Type: NASA/TM-2012-216001 , ARC-E-DAA-TN4654
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    Verification of Small Hole Theory for Application to Wire Chaffing Resulting in Shield Faults (2011)
    In:  CASI
    Details
    Publication Date: 2019-08-13
    Description: Our work is focused upon developing methods for wire chafe fault detection through the use of reflectometry to assess shield integrity. When shielded electrical aircraft wiring first begins to chafe typically the resulting evidence is small hole(s) in the shielding. We are focused upon developing algorithms and the signal processing necessary to first detect these small holes prior to incurring damage to the inner conductors. Our approach has been to develop a first principles physics model combined with probabilistic inference, and to verify this model with laboratory experiments as well as through simulation. Previously we have presented the electromagnetic small-hole theory and how it might be applied to coaxial cable. In this presentation, we present our efforts to verify this theoretical approach with high-fidelity electromagnetic simulations (COMSOL). Laboratory observations are used to parameterize the computationally efficient theoretical model with probabilistic inference resulting in quantification of hole size and location. Our efforts in characterizing faults in coaxial cable are subsequently leading to fault detection in shielded twisted pair as well as analysis of intermittent faulty connectors using similar techniques.
    Keywords: Electronics and Electrical Engineering
    Type: ARC-E-DAA-TN3247 , Aircraft Airworthiness and Sustainment; Apr 17, 2011 - Apr 29, 2011; San Diego,CA; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 7
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    The Planned Soil Moisture Active Passive (SMAP) Mission L-Band Radar/Radiometer Instrument (2011)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The Soil Moisture Active/Passive (SMAP) mission is a NASA mission identified by the NRC 'decadal survey' to measure both soil moisture and freeze/thaw state from space. The mission will use both active radar and passive radiometer instruments at L-Band. In order to achieve a wide swath at sufficiently high resolution for both active and passive channels, an instrument architecture that uses a large rotating reflector is employed. The instrument system has completed the preliminary design review (PDR) stage, and detailed instrument design has begun. In addition to providing an overview of the instrument design, two recent design modifications are discussed: 1) The addition of active thermal control to the instrument spun side to provide a more stable, settable thermal environment for the radiometer electronics, and 2) A 'sequential transmit' strategy for the two radar polarization channels which allows a single high-power amplifier to be used.
    Keywords: Communications and Radar; Earth Resources and Remote Sensing; Instrumentation and Photography
    Type: 2011 IEEE International Geoscience and Remote Sensing Symposium (IGARSS 2011); Jul 24, 2011 - Jul 29, 2011; Vancouver, BC; Canada
    Format: text
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    NASA TECHNICAL REPORTS
  • 8
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    An Adaptive Nonlinear Aircraft Maneuvering Envelope Estimation Approach for Online Applications (2014)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A nonlinear aircraft model is presented and used to develop an overall unified robust and adaptive approach to passive trim and maneuverability envelope estimation with uncertainty quantification. The concept of time scale separation makes this method suitable for the online characterization of altered safe maneuvering limitations after impairment. The results can be used to provide pilot feedback and/or be combined with flight planning, trajectory generation, and guidance algorithms to help maintain safe aircraft operations in both nominal and off-nominal scenarios.
    Keywords: Aircraft Stability and Control; Aircraft Design, Testing and Performance
    Type: ARC-E-DAA-TN11537 , SciTech 2014; Jan 13, 2014 - Jan 17, 2014; National Harbor, Maryland; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 9
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    A Model-Based Probabilistic Inversion Framework for Wire Fault Detection Using TDR (2010)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Time-domain reflectometry (TDR) is one of the standard methods for diagnosing faults in electrical wiring and interconnect systems, with a long-standing history focused mainly on hardware development of both high-fidelity systems for laboratory use and portable hand-held devices for field deployment. While these devices can easily assess distance to hard faults such as sustained opens or shorts, their ability to assess subtle but important degradation such as chafing remains an open question. This paper presents a unified framework for TDR-based chafing fault detection in lossy coaxial cables by combining an S-parameter based forward modeling approach with a probabilistic (Bayesian) inference algorithm. Results are presented for the estimation of nominal and faulty cable parameters from laboratory data.
    Keywords: Electronics and Electrical Engineering
    Type: ARC-E-DAA-TN1389 , ARC-E-DAA-TN955 , 2010 IEEE Instrumentation and Measurement Technology Conference - I2MTC 2010; May 03, 2010 - May 06, 2010; Austin, TX; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 10
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    Optimized Algorithms for Prediction Within Robotic Tele-Operative Interfaces (2010)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: Robonaut, the humanoid robot developed at the Dexterous Robotics Labo ratory at NASA Johnson Space Center serves as a testbed for human-rob ot collaboration research and development efforts. One of the recent efforts investigates how adjustable autonomy can provide for a safe a nd more effective completion of manipulation-based tasks. A predictiv e algorithm developed in previous work was deployed as part of a soft ware interface that can be used for long-distance tele-operation. In this work, Hidden Markov Models (HMM?s) were trained on data recorded during tele-operation of basic tasks. In this paper we provide the d etails of this algorithm, how to improve upon the methods via optimization, and also present viable alternatives to the original algorithmi c approach. We show that all of the algorithms presented can be optim ized to meet the specifications of the metrics shown as being useful for measuring the performance of the predictive methods. 1
    Keywords: Cybernetics, Artificial Intelligence and Robotics
    Type: NASA/TM-?2010-?216417 , ARC-E-DAA-TN2484
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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