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  • 1
    Electronic Resource
    Electronic Resource
    Enhanced vision for adverse weather aircraft landing (1996)
    Springer
    International journal of infrared and millimeter waves 17 (1996), S. 1-50 
    Details
    ISSN: 1572-9559
    Keywords: Autonomous landing ; Enhanced vision ; Image enhancement ; Image processing ; Imaging radar ; Real-time signal processing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Landing in poor weather is a crucial problem for the air transportation system of the future. To aid the pilots for these conditions several solutions have been suggested and/or implemented including instrument landing system(ILS) and microwave landing system(MLS) that put the responsibility of the landing to a large extent in the hands of the airport facilities. These systems even though useful are not available due to their high costs except in few major metropolitan airports. This shortcoming has generated interest in providing all weather capabilities not on the landing facility but on the vehicle itself. The Synthetic Vision System Technology Demonstration sponsored by the United States Federal Aviation Administration(FAA) and the US Air Force represents an effort to respond to the above needs[1,2]. In this paper we present a summary of a typical synthetic vision system. This system consists of a scanning 35GHz radar a scanning antenna, a signal/image processor and a head up display(HUD). The pilot is presented a final perspective image of the scene sensed by the radar with associated flight guidance symbology. This systems is implemented in real time hardware and has been under going tower and flight testing under a variety of weather conditions since early 1992.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02088181
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    Paper (German National Licenses)
    Fulltext
  • 2
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    Enhanced vision for adverse weather aircraft landing (1996)
    Springer
    Details
    Publication Date: 1996-01-01
    Print ISSN: 1866-6892
    Electronic ISSN: 1866-6906
    Topics: Physics
    Published by Springer
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    PAPER CURRENT
  • 3
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    Beyond singular values and loop shapes (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The status of singular value loop-shaping as a design paradigm for multivariable feedback systems is reviewed. It shows that this paradigm is an effective design tool whenever the problem specifications are spacially round. The tool can be arbitrarily conservative, however, when they are not. This happens because singular value conditions for robust performance are not tight (necessary and sufficient) and can severely overstate actual requirements. An alternate paradign is discussed which overcomes these limitations. The alternative includes a more general problem formulation, a new matrix function mu, and tight conditions for both robust stability and robust performance. The state of the art currently permits analysis of feedback systems within this new paradigm. Synthesis remains a subject of research.
    Keywords: CYBERNETICS
    Type: Journal of Guidance, Control, and Dynamics (ISSN 0731-5090); 14; 5-16
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Design of feedback control systems for stable plants with saturating actuators (1988)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A systematic control design methodology is introduced for multi-input/multi-output stable open loop plants with multiple saturations. This new methodology is a substantial improvement over previous heuristic single-input/single-output approaches. The idea is to introduce a supervisor loop so that when the references and/or disturbances are sufficiently small, the control system operates linearly as designed. For signals large enough to cause saturations, the control law is modified in such a way as to ensure stability and to preserve, to the extent possible, the behavior of the linear control design. Key benefits of the methodology are: the modified compensator never produces saturating control signals, integrators and/or slow dynamics in the compensator never windup, the directional properties of the controls are maintained, and the closed loop system has certain guaranteed stability properties. The advantages of the new design methodology are illustrated in the simulation of an academic example and the simulation of the multivariable longitudinal control of a modified model of the F-8 aircraft.
    Keywords: CYBERNETICS
    Type: NASA-CR-182613 , NAS 1.26:182613 , LIDS-P-1756
    Format: application/pdf
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  • 5
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    A method for designing robust multivariable feedback systems (1988)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A new methodology is developed for the synthesis of linear, time-invariant (LTI) controllers for multivariable LTI systems. The aim is to achieve stability and performance robustness of the feedback system in the presence of multiple unstructured uncertainty blocks; i.e., to satisfy a frequency-domain inequality in terms of the structured singular value. The design technique is referred to as the Causality Recovery Methodology (CRM). Starting with an initial (nominally) stabilizing compensator, the CRM produces a closed-loop system whose performance-robustness is at least as good as, and hopefully superior to, that of the original design. The robustness improvement is obtained by solving an infinite-dimensional, convex optimization program. A finite-dimensional implementation of the CRM was developed, and it was applied to a multivariate design example.
    Keywords: CYBERNETICS
    Type: NASA-CR-182459 , NAS 1.26:182459 , LIDS-P-1749
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    Design of feedback control systems for unstable plants with saturating actuators (1988)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A new control design methodology is introduced for multi-input/multi-output systems with unstable open loop plants and saturating actuators. A control system is designed using well known linear control theory techniques and then a reference prefilter is introduced so that when the references are sufficiently small, the control system operates linearly as designated. For signals large enough to cause saturations, the control law is modified in such a way to ensure stability and to preserve, to the extent possible, the behavior of the linear control design. Key benefits of this methodology are: the modified feedback system never produces saturating control signals, integrators and/or slow dynamics in the compensator never windup, the directionaL properties of the controls are maintained, and the closed loop system has certain guaranteed stability properties. The advantages of the new design methodology are illustrated in the simulation of an approximation of the AFTI-16 (Advanced Fighter Technology Integration) aircraft multivariable longitudinal dynamics.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: NASA-CR-183392 , NAS 1.26:183392 , Symposium on Nonlinear Control Systems Design; Jan 01, 1989; Cambridge, MA; United States
    Format: application/pdf
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  • 7
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    A frequency-domain estimator for use in adaptive control systems (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The paper presents a frequency-domain estimator which can identify both a nominal model of a plant as well as a frequency-domain bounding function on the modeling error associated with this nominal model. This estimator, which is called a robust estimator, can be used in conjunction with a robust control-law redesign algorithm to form a robust adaptive controller.
    Keywords: CYBERNETICS
    Type: 1987 American Control Conference; Jun 10, 1987 - Jun 12, 1987; Minneapolis, MN; United States
    Format: text
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    NASA TECHNICAL REPORTS
  • 8
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    A frequency-domain estimator for use in adaptive control systems (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: This paper presents a frequency-domain estimator that can identify both a parametrized nominal model of a plant as well as a frequency-domain bounding function on the modeling error associated with this nominal model. This estimator, which we call a robust estimator, can be used in conjunction with a robust control-law redesign algorithm to form a robust adaptive controller.
    Keywords: CYBERNETICS
    Type: Automatica (ISSN 0005-1098); 27; 23-38
    Format: text
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    NASA TECHNICAL REPORTS
  • 9
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    The LQR/LTR procedure for multivariable feedback control design (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: This paper provides a tutorial overview of the linear quadratic Gaussian with loop transfer recovery (LQG/LTR) design procedure for linear multivariable feedback systems. LQR/LTR is interpreted as the solution of a specific weighted H-squared tradeoff between transfer functions in the frequency domain. Properties of this solution are examined for both minimum-phase and nonminimum-phase systems. This leads to a formal weight augmentation procedure for the minimum-phase case which permits essentially arbitrary specification of system sensitivity functions in terms of the weights. While such arbitrary specifications are not possible for nonminimum-phase problems, a direct relationship between weights and sensitivities is developed for nonminimum-phase SISO and certain nonminimum-phase MIMO cases which guides the weight selection process.
    Keywords: CYBERNETICS
    Type: IEEE Transactions on Automatic Control (ISSN 0018-9286); AC-32; 105-114
    Format: text
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    NASA TECHNICAL REPORTS
  • 10
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    A method for designing robust multivariable feedback systems (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A new methodology is developed for the synthesis of linear, time-invariant (LTI) controllers for multivariable LTI systems. The aim is to achieve stability and performance robustness of the feedback system in the presence of multiple unstructured uncertainty blocks; i.e., to satisfy a frequency-domain inequality in terms of the structured singular value. The design technique is referred to as the causality recovery methodology (CRM). Starting with an initial (nominally) stabilizing compensator, the CRM produces a closed-loop system whose performance-robustness is at least as good as, and hopefully superior to, that of the original design. The robustness improvement is obtained by solving an infinite-dimensional, convex optimization program. A finite-dimensional implementation of the CRM was developed, and it was applied to a multivariate design example.
    Keywords: CYBERNETICS
    Type: IEEE Conference on Decision and Control; Dec 07, 1988 - Dec 09, 1988; Austin, TX; United States
    Format: text
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