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SENSITIVITY CONTROLLER FOR UNCERTAIN SYSTEMS

JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1990年第2期13卷 321-329页

作者： OKADA, K SKELTON, RE PURDUE UNIV DEPT AERONAUT & ASTRONAUTW LAFAYETTEIN 47906

In this paper a new controller design, which we Shall call the "trajectory sensitivity optimization" method, is presented to improve the robustness for parameter variations. The method uses the sensitivity trajectory to model the parameter uncertainty and introduces a special quadratic cost function involving an input and output sensitivity term. Necessary conditions are derived to obtain the dynamic controller. The necessary conditions consist of two Lyapunov equations and two controller gain equations that have no closed-form solution. Therefore, a special iterative algorithm was developed to obtain the numerical solution. The method can deal with a wider class of parameter uncertainty than existing methods. numerical examples show that the method is effective in improving the robustness to parameter variations. © 1990 American Institute of Aeronautics and Astronautics, Inc., All rights reserved.

关键词： Closed Loop System Iterative Algorithm Linear Quadratic Gaussian Simply Supported Beams Multivariable Control Flexible Structures White Noise Lagrange Multipliers numerical algorithms Riccati Equations

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OPTIMAL REDUCED-ORDER OBSERVER-ESTIMATORS

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1990年第6期13卷 1126-1135页

作者： HADDAD, WM BERNSTEIN, DS HARRIS CORP DIV GOVT AEROSP SYSTMELBOURNEFL 32902

This paper presents a unified approach to designing reduced-order observer-estimators. Specifically, we seek to design a reduced-order estimator satisfying an observation constraint that involves a prespecified, possibly unstable, subspace of the system dynamics and that also yields reudced-order estimates of the remaining subspace. The results are obtained by merging the optimal projection approach to reduced-order estimation of Bernstein and Hyland with the subspace-observer results of Bernstein and Haddad. A salient feature of this theory is the treatment of unstable dynamics within reduced-order state-estimation theory. In contrast to the standard full-order estimation problem involving a single algebraic Riccati equation, the solution to the reduced-order observer-estimator problem involves an algebraic system of four equations consisting of one modified Riccati equation and three modified Lyapunov equations coupled by two distinct oblique projections.

关键词： Riccati Equations Observability Gramian Algebraic Riccati Equation Kalman Filter Gain numerical algorithms White Noise Lagrange Multipliers Rigid Body Dynamics Space Structures Feedback Control

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ANALYTICAL MODELS FOR RELATIVE MOTION UNDER CONSTANT THRUST

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1990年第4期13卷 644-650页

作者： VANDERHA, J ESA Darmstadt Federal Republic of Germany

A general formulation for the relative motion allowing for arbitrary perturbing or thrust forces on each of the vtwo satellites is presented. Exact as well as approximate perturbation solutions for the linearized relative motion vequations with constant radial or circumferential forces acting on the subsatellite are established. The validity vand usefulness of these solutions is assessed for a few realistic applications related to the European Space vAgency's retrievable carrier (EURECA) rendezvous maneuvering with the Shuttle. The results are of general vinterest for the fast calculation of relative subsatellite motion under thrust forces. © 1990 American Institute of Aeronautics and Astronautics, Inc., All rights reserved.

关键词： Thrust Satellites European Space Agency Clohessy Wiltshire Equation numerical algorithms Orbital Elements Earth numerical Integration Newton's Second Law Attitude Control

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ROLE OF MAGGI EQUATIONS IN COMPUTATIONAL METHODS FOR CONSTRAINED MULTIBODY SYSTEMS

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1990年第1期13卷 113-120页

作者： KURDILA, A PAPASTAVRIDIS, JG KAMAT, MP GEORGIA INST TECHNOL ENGN SCI & MECH GRPATLANTAGA 30332 GEORGIA INST TECHNOL ENGN SCI & MECH GRPATLANTAGA 30332 GEORGIA INST TECHNOL SCH MECH ENGNATLANTAGA 30332 GEORGIA INST TECHNOL SCH AEROSP ENGNATLANTAGA 30332

This paper presents a unified theoretical basis for a class of methods that generate the governing equations of constrained dynamical systems by eliminating the constraints. By using Maggi's equations in conjunction with a common projective theory from numerical analysis, it is shown that members of the class are precisely characterized by the basis they choose for the null-space of the variational form of the constraints. For each method considered, the specific basis chosen for the null-space of the variational constraints is derived, as well as a dual basis for the orthogonal complement. The latter basis is of particular interest since it is shown that its knowledge theoretically enables one to generalize certain methods of the class to calculate constraint forces and torques. Practical approaches based on orthogonal transformations to effect this strategy are also outlined. In addition, since the theory presented herein stresses a common, fundamental structure to the various methods, it is especially useful as a means of comparing and evaluating individual numerical algorithms. The theory presented makes clear the relationship between certain numerical instabilities that have been noted in some methods that eliminate a priori constraint contributions to the governing equations by selecting an independent subset of unknowns. It is also briefly indicated how this formalism can be extended, in principle, to the wider class of nonlinear nonholonomic constraints. © 1990 American Institute of Aeronautics and Astronautics, Inc., All rights reserved.

关键词： Computational Methods Multibody System numerical algorithms Singular Value Decomposition Mechanism Dynamics Newton's Second Law Large Space Structures Holonomic Constraints numerical Simulation Digital Computers

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ANALYTIC RELATION FOR THE HOLSTEIN-BOHLEN PRESSURE-GRADIENT PARAMETER

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AIAA JOURNAL 1990年第10期28卷 1824-1826页

作者： JONES, E University of Maryland College Park Maryland 20742

The classic integral boundary-layer method of Holstein and Bohlen is presented in many texts such as White. The method, while unsatisfactory in some respects, still has academic interest. It was, of course, conceived in an era where hand calculations were necessary. Therefore, the fact that the expressions for the boundary-layer quantities of interest are expressed in terms of the pressure-gradient parameter, Λ for the von Karman-Pohlhausen method instead of the pressure gradient parameter K for the Holstein-Bohlen method, presents no significant difficulty. In order to avoid table look-up operations in computer codes, a function Λ(K) would allow routine calculations for all quantities. The analysis reported here resulted in a relatively simple, accurate correlation for Λ(K).

关键词： Pressure Gradient Velocity Profiles Incompressible Flow Delta Wing Riemann Problem Vortices Boundary Layer Thickness numerical algorithms Euler Equations Mach Number

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APPLICATION OF LOAD-DEPENDENT VECTORS BASES FOR DYNAMIC SUBSTRUCTURE-ANALYSIS

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AIAA JOURNAL 1990年第1期28卷 177-179页

作者： LEGER, P McGill University Montreal Quebec Canada

The purpose of this Note is to discuss practical implementation aspects of dynamic substructuring method related to the algorithm used to generate transformation vectors and the corresponding evaluation of error norms. A new computational variant that combines the subspace generation of load-dependent vectors and the static condensation technique is developed to compute global modes which are not a summation of local modes or a combination of substructure modes. Finally, a numerical example of a simple cantilever structure is presented to illustrate the relative performance of the proposed solution methods.

关键词： Stiffness Matrices Dynamic Substructuring Structural Response Beam (Structures) Condensation Condensation Algorithm numerical algorithms Lagrange Multipliers Structural System Dynamic Analysis

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Parallel algorithms for Matrix Computations

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丛书名： Other Titles in Applied Mathematics

1990年

作者： R. J. Plemmons

ISBN: (数字)9781611971705

ISBN: (纸本)9780898712605

Describes a selection of important parallel algorithms for matrix computations. Reviews the current status and provides an overall perspective of parallel algorithms for solving problems arising in the major areas of numerical linear algebra, including (1) direct solution of dense, structured, or sparse linear systems, (2) dense or structured least squares computations, (3) dense or structured eigenvaluen and singular value computations, and (4) rapid elliptic solvers. The book emphasizes computational primitives whose efficient execution on parallel and vector computers is essential to obtain high performance algorithms.

Consists of two comprehensive survey papers on important parallel algorithms for solving problems arising in the major areas of numerical linear algebra—direct solution of linear systems, least squares computations, eigenvalue and singular value computations, and rapid elliptic solvers, plus an extensive up-to-date bibliography (2,000 items) on related research.

关键词： sparse linear systems linear algebra numerical algorithms

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SUBOPTIMAL FEEDBACK VIBRATION CONTROL OF A BEAM WITH A PROOF-MASS ACTUATOR

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1989年第5期12卷 691-697页

作者： POLITANSKY, H PILKEY, WD MINIST DEF HAIFAISRAEL

A clamped-free beam, damped by a proof-mass actuator, is selected for small-scale model research of flexible structures in space. Because of the short length of the actuator, the dynamic behavior of this system is strongly influenced by the constraints on the motion of the proof mass and by the maximum control forces available. An optimal solution is presented, in which a linear programming algorithm is used. Then, by special consideration of the constraints, a simplified suboptimal feedback position control is used, controlling the system by imposing position commands on the proof mass rather than using direct force inputs. The resulting time response closely fits the optimal solution. An adequate response is achieved in the linear and nonlinear regions, even when the proof mass violates its constraints.

关键词： Actuators numerical algorithms Vibration Control Flexible Structures Modern Control Theory Algebraic Riccati Equation Accelerometer Large Space Structures Electromagnetic Forces Real Time System

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AUXILIARY LINEAR MULTISTEP METHODS - EXPLICIT

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INTERNATIONAL JOURNAL OF COMPUTER MATHEMATICS 1989年第2期26卷 101-115页

作者： SAHOO, G DATTA, N Department of Mathematics Indian Institute of Technology Kharagpur-72 1302 India

A class of high order explicit 2-step methods for the integration of ordinary differential equations have been developed. The methods use the slopes at several auxiliary points within a step. The efficiency of the methods has been established by comparing numerical results with those of Adams—Bashforth—Moulton predictor-corrector method and Runge-Kutta fourth order method.

关键词： Ordinary differential equations initial value problems multistep methods hybrid methods numerical algorithms zero-stability order and accuracy numerical experiments G.1.0 G.1.7

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ANALYSIS OF FLUX-SPLIT algorithms FOR EULERS EQUATIONS WITH REAL GASES

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AIAA JOURNAL 1989年第5期27卷 524-531页

作者： GROSSMAN, B WALTERS, RW Virginia Polytechnic Institute and State University Blacksburg Virginia

An analysis of flux-splitting procedures for the solution of Euler′s equations with real gas effects is presented. An alternative real gas flux splitting is derived which can easily be implemented into existing codes. This approach, which takes the form of an “equivalent” γ representation is not an ad hoc model, but is based on theoretical considerations. Details of this method with the Steger-Warming and Van Leer flux-vector splittings and the Roe flux-difference splitting are given. Applications of the method to several high Mach number, high-temperature, equilibrium airflows are presented for one and two space dimensions. © 1989 American Institute of Aeronautics and Astronautics, Inc., All rights reserved.

关键词： Euler Equations Freestream Conditions Perfect Gas Computational Fluid Dynamics Chemical Equilibrium Internal Flows Total Energy Atmospheric Conditions Stagnation Enthalpy numerical algorithms

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