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  • 1
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    Robust Stabilization of a Class of passive Nonlinear Systems (1996)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The problem of feedback stabilization is considered for a class of nonlinear, finite dimensional, time invariant passive systems that are affine in control. Using extensions of the Kalman-Yakubovch lemma, it is shown that such systems can be stabilized by a class of finite demensional, linear, time-invariant controllers which are strictly positive real in the weak or marginal sense. The stability holds regardless of model uncertainties, and is therefore, robust.
    Keywords: Cybernetics
    Type: NASA-TM-110287 , NAS 1.15:110287
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  • 2
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    On longitudinal control of high speed aircraft in the presence of aeroelastic modes (1996)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Longitudinal control system design is considered for a linearized dynamic model of a supersonic transport aircraft concept characterized by relaxed static stability and significant aeroelastic interactions. Two LQG-type controllers are designed using the frequency-domain additive uncertainty formulation to ensure robustness to unmodeled flexible modes. The first controller is based on a 4th-order model containing only the rigid-body modes, while the second controller is based on an 8th-order model that additionally includes the two most prominent flexible modes. The performance obtainable from the 4th-order controller is not adequate, while the 8th-order controller is found to provide better performance. Frequency-domain and time-domain (Lyapunov) methods are subsequently used to assess the robustness of the 8th-order controller to parametric uncertainties in the design model.
    Keywords: Aircraft Stability and Control
    Type: NASA-TM-110254 , NAS 1.15:110254
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  • 3
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    Robust control of nonlinear flexible multibody systems using quaternion feedback and dissipative compensation (1994)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Global asymptotic stability of a class of nonlinear multibody flexible space structures under dissipative compensation is established. Two cases are considered. The first case allows unlimited nonlinear motions of the entire system and uses quaternion feedback. The second case assumes that the central body motion is in the linear range although the other bodies can undergo unrestricted nonlinear motion. The stability is proved to be robust to the inherent modeling nonlinearities and uncertainties. Furthermore, for the second case, the stability is also shown to be robust to certain actuator and sensor nonlinearities. The stability proofs use the Lyapunov approach and exploit the inherent passivity of such systems. The results are applicable to a wide class of systems, including flexible space structures with articulated flexible appendages.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-TM-109099 , NAS 1.15:109099
    Format: application/pdf
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  • 4
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    Computing maximum tracking error due to payload dynamics (1990)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The determination of maximum endpoint tracking error due to uncompensated inertial payload dynamics is investigated. The problem is formulated on the basis of well-known kinetic and kinematic relationships with constraints on maximum joint positions and velocities as well as the generalized force/speed constraint relationship for each actuator. An endpoint tracking error objective function is formed, and numerical optimization is used to determine the maximum. An example computation is presented to show the tracking error under progressively increasing payload using a PUMA 560 manipulator with its first three joints in motion.
    Keywords: CYBERNETICS
    Format: text
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  • 5
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    Robust control of nonlinear flexible multibody systems using quaternion feedback and dissipative compensation (1994)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Global asymptotic stability of a class of nonlinear multibody flexible space-stnuctures under dissipative compensation is established. Two cases are considered. The first case allows unlimited nonlinear motions of the entire system and uses quaternion feedback. The second case assumes that the central body motion is in the linear range although the other bodies can undergo unrestricted nonlinear motion. The stability is proved to be robust to the inherent modeling nonlinearities and uncertainties. Furthermore for the second case the stability is also shown to be robust to certain actuator and sensor nonlinearities. The stability proofs use the Lyapunov approach and exploit the inherent passivity of such systems. The results are applicable to a wide class of systems including flexible space-structures with articulated flexible appendages.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-TM-109099 , NAS 1.15:109099
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  • 6
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    Mathematical modeling of a class of multibody flexible spacecraft structures (1994)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: A mathematical model for a general multibody flexible spacecraft is obtained. The generic spacecraft considered consists of a flexible central body to which a number of flexible multibody structures are attached. The coordinate systems used in the derivation allow effective decoupling of the translational motion of the entire spacecraft from its rotational motion about its center of mass. The derivation assumes that the deformations in the bodies are only due to elastic motions. The dynamic model derived is a closed-form vector-matrix differential equation. The model developed can be used for analysis and simulation of many realistic spacecraft configurations.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-TM-109166 , NAS 1.15:109166
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  • 7
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    Optimal control/structure integrated design of a flexible space platform with articulated appendages (1991)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A complete set of closed form symbolic equations are developed for a 2-D model of a system comprised of a flexible platform with articulated appendages. The system considered has a flexible two link manipulator, with joint compliance, at one end of the flexible platform and an articulated antenna on the other end. The model is formulated using a Lagrangian approach which incorporates homogeneous transformation matrices, similar to those typically seen in the robotics literature, for the kinematic representation. The integrated control/structure design strategy considered emphasizes rapid system response and minimal structural weight. Constraints are included to keep antenna pointing error to a minimum, and at the same time achieve accurate end point positioning of the manipulator with minimal oscillations.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: In: Structures sensing and control; Proceedings of the Meeting, Orlando, FL, Apr. 2, 3, 1991 (A93-22001 07-35); p. 243-253.
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  • 8
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    A class of stabilizing controllers for flexible multibody systems (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The problem of controlling a class of nonlinear multibody flexible space systems consisting of a flexible central body to which a number of articulated appendages are attached is considered. Collocated actuators and sensors are assumed, and global asymptotic stability of such systems is established under a nonlinear dissipative control law. The stability is shown to be robust to unmodeled dynamics and parametric uncertainties. For a special case in which the attitude motion of the central body is small, the system, although still nonlinear, is shown to be stabilized by linear dissipative control laws. Two types of linear controllers are considered: static dissipative (constant gain) and dynamic dissipative. The static dissipative control law is also shown to provide robust stability in the presence of certain classes of actuator and sensor nonlinearities and actuator dynamics. The results obtained for this special case can also be readily applied for controlling single-body linear flexible space structures. For this case, a synthesis technique for the design of a suboptimal dynamic dissipative controller is also presented. The results obtained in this paper are applicable to a broad class of multibody and single-body systems such as flexible multilink manipulators, multipayload space platforms, and space antennas. The stability proofs use the Lyapunov approach and exploit the inherent passivity of such systems.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-TP-3494 , L-17413 , NAS 1.60:3494
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  • 9
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    Three-axis stabilization of spacecraft using parameter-independent nonlinear quaternion feedback (1994)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This paper considers the problem of rigid spacecraft. A nonlinear control law which uses the feedback of the unit quaternion and the measured angular velocities is proposed and is shown to provide global asymptotic stability. The control law does not require the knowledge of the system parameters, and is therefore robust to modeling errors. The significance of the control law is that it can be used for large-angle maneuvers with guaranteed stability.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-TM-109150 , NAS 1.15:109150
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  • 10
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    Further Investigation of Receding Horizion-Based Controllers and Neural Network-Based Systems (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This report provides a comprehensive summary of the research work performed over the entire duration of the co-operative research agreement between NASA Langley Research Center and Kansas State University. This summary briefly lists the findings and also suggests possible future directions for the continuation of the subject research in the area of Generalized Predictive Control (GPC) and Network Based Generalized Predictive Control (NGPC).
    Keywords: Cybernetics, Artificial Intelligence and Robotics
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