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  • 1
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    Rescheduling with iterative repair (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: This paper presents a new approach to rescheduling called constraint-based iterative repair. This approach gives our system the ability to satisfy domain constraints, address optimization concerns, minimize perturbation to the original schedule, and produce modified schedules quickly. The system begins with an initial, flawed schedule and then iteratively repairs constraint violations until a conflict-free schedule is produced. In an empirical demonstration, we vary the importance of minimizing perturbation and report how fast the system is able to resolve conflicts in a given time bound. These experiments were performed within the domain of Space Shuttle ground processing.
    Keywords: CYBERNETICS
    Type: NASA. Ames Research Center, Working Notes from the 1992 AAAI Spring Symposium on Practical Approaches to Scheduling and Planning; p 92-96
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Reliable design of H-2 optimal reduced-order controllers via a homotopy algorithm (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Due to control processor limitations, the design of reduced-order controllers is an active area of research. Suboptimal methods based on truncating the order of the corresponding linear-quadratic-Gaussian (LQG) compensator tend to fail if the requested controller dimension is sufficiently small and/or the requested controller authority is sufficiently high. Also, traditional parameter optimization approaches have only local convergence properties. This paper discusses a homotopy algorithm for optimal reduced-order control that has global convergence properties. The exposition is for discrete-time systems. The algorithm has been implemented in MATLAB and is applied to a benchmark problem.
    Keywords: CYBERNETICS
    Type: In: Controls for optical systems; Proceedings of the Meeting, Orlando, FL, Apr. 21, 22, 1992 (A93-34276 13-74); p. 116-127.
    Format: text
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  • 3
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    Learning to improve iterative repair scheduling (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This paper presents a general learning method for dynamically selecting between repair heuristics in an iterative repair scheduling system. The system employs a version of explanation-based learning called Plausible Explanation-Based Learning (PEBL) that uses multiple examples to confirm conjectured explanations. The basic approach is to conjecture contradictions between a heuristic and statistics that measure the quality of the heuristic. When these contradictions are confirmed, a different heuristic is selected. To motivate the utility of this approach we present an empirical evaluation of the performance of a scheduling system with respect to two different repair strategies. We show that the scheduler that learns to choose between the heuristics outperforms the same scheduler with any one of two heuristics alone.
    Keywords: CYBERNETICS
    Type: NASA-TM-108118 , FIA-92-14 , NAS 1.15:108118
    Format: application/pdf
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  • 4
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    Scheduling and rescheduling with iterative repair (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This paper describes the GERRY scheduling and rescheduling system being applied to coordinate Space Shuttle Ground Processing. The system uses constraint-based iterative repair, a technique that starts with a complete but possibly flawed schedule and iteratively improves it by using constraint knowledge within repair heuristics. In this paper we explore the tradeoff between the informedness and the computational cost of several repair heuristics. We show empirically that some knowledge can greatly improve the convergence speed of a repair-based system, but that too much knowledge, such as the knowledge embodied within the MIN-CONFLICTS lookahead heuristic, can overwhelm a system and result in degraded performance.
    Keywords: CYBERNETICS
    Type: NASA-TM-108120 , FIA-92-16 , NAS 1.15:108120
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  • 5
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    A parameterization of minimal plants (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The authors present the input-normal Riccati parameterization which allows a minimal plant (A, B, C, D) to be represented completely by its B, C, and D matrices. In addition to the basic parameterization, they present useful gradient expressions for a cost functional J(A, B, C, D) when the plant is restricted to the input-normal Riccati form. The parameterization is valid for both stable and unstable, and continuous-time and discrete-time systems.
    Keywords: CYBERNETICS
    Type: In: 1992 American Control Conference, 11th, Chicago, IL, June 24-26, 1992, Proceedings. Vol. 1 (A93-22776 07-63); p. 355, 356.
    Format: text
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  • 6
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    Rescheduling with iterative repair (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This paper presents a new approach to rescheduling called constraint-based iterative repair. This approach gives our system the ability to satisfy domain constraints, address optimization concerns, minimize perturbation to the original schedule, produce modified schedules, quickly, and exhibits 'anytime' behavior. The system begins with an initial, flawed schedule and then iteratively repairs constraint violations until a conflict-free schedule is produced. In an empirical demonstration, we vary the importance of minimizing perturbation and report how fast the system is able to resolve conflicts in a given time bound. We also show the anytime characteristics of the system. These experiments were performed within the domain of Space Shuttle ground processing.
    Keywords: CYBERNETICS
    Type: NASA-TM-108119 , FIA-92-15 , NAS 1.15:108119
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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