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Impact Time and Angle Control Against Moving Targets with Look Angle Shaping

JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2020年第5期43卷 1020-1025页

作者： Tekin, Raziye Erer, Koray S. Middle East Tech Univ Elect & Elect Engn Dept TR-06800 Ankara Turkey Roketsan Missiles Inc Tact Missile Syst TMS Guidance Syst Design Dept TR-06780 Ankara Turkey AIAA Reston VA 20191 USA

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New method for accurate and consistent identification of modal parameters

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1996年第5期19卷 992-999页

作者： Lin, RM Ling, SF Nanyang Technological University Singapore 2263 Singapore

A new method for the estimation of modal parameters is presented. Unlike the majority of existing methods, which involve complicated curvefitting and interpolative procedures, the proposed method calculates the modal parameters by solving the eigenvalue problem of an equivalent eigensystem derived from measured frequency response function (FRF) data. Tt is developed based on the practical assumption that only one incomplete column of the FRF matrix of the test structure has been measured in a frequency range of interest. All measured FRFs are used simultaneously to construct the equivalent eigensystem matrices from which natural frequencies, damping loss factors, and mode shape vectors of interest are solved. Because the identification problem is reduced to an eigenvalue problem of an equivalent system, natural frequencies and damping loss factors identified are consistent. Further procedures for normalizing the identified eigenvectors so that they become mass normalized are developed. Applications of the method to both numerically simulated and practically measured FRF data are given to demonstrate the practicality of the proposed method, and the results obtained are indeed very promising.

关键词： Frequency Response Functions Finite Element Analysis Beam (Structures) Modal Analysis Mathematical Models Eigensystem Realization Algorithm Structural Damping numerical algorithms Structural Modeling Material Properties

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Algorithm to integrate the Ffowcs Williams-Hawkings equation on supersonic rotating domain

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AIAA JOURNAL 1999年第9期37卷 1040-1047页

作者： Ianniello, S Ctr Italiano Ric Aerosp Aeroacoust Branch I-81043 Capua Italy

The numerical solution of the Ffowcs Williams-Hawkings equation (Ffowcs Williams, J. E., and Hawkings, D. L., "Sound Generation by Turbulence and Surfaces in Arbitrary Motion," Philosophical Transactions of the Royal Society, Vol. A264, No. 1151, 1969, pp. 321-342) on a rotating supersonic domain is discussed. Based on the emission-surface algorithm, the adopted solver performs the integration on the so-called acoustic domain to avoid the Doppler singularity in the integral kernels. The presence of multiple emission times for the supersonic source points and the particular time evolution of the integration domain force the use of a particular data-fitting procedure on both the geometrical and integral quantities. The algorithm may he used in the numerical prediction of the quadrupole source term for helicopter rotors operating at a high transonic regime and in the aeroacoustic analysis of the modern propeller blades, rotating at supersonic tip speed.

关键词： Helicopter Rotor Propeller Blades Computing Mach Numbers NACA 0012 numerical algorithms Green's Function Regular Grid Rotor Blades Propfan

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Stochastic optimal control via Bellman's principle

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AUTOMATICA 2003年第12期39卷 2109-2114页

作者： Crespo, LG Sun, JQ Natl Inst Aerosp Hampton VA 23666 USA Univ Delaware Dept Engn Mech Newark DE 19711 USA

This paper presents a strategy for finding optimal controls of non-linear systems subject to random excitations. The method is capable to generate global control solutions when state and control constraints are present. The solution is global in the sense that controls for all initial conditions in a region of the state space are obtained. The approach is based on Bellman's principle of optimality, the cumulant neglect closure method and the short-time Gaussian approximation. Problems with state-dependent diffusion terms, non-closeable hierarchies of moment equations for the states and singular state boundary condition are considered in the examples. The uncontrolled and controlled system responses are evaluated by creating a Markov chain with a control dependent transition probability matrix via the generalized cell mapping method. In all numerical examples, excellent controlled performances were obtained. (C) 2003 Elsevier Ltd. All rights reserved.

关键词： stochastic control optimality non-linearity random processes numerical algorithms random vibrations

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A FAST DOT-PRODUCT ALGORITHM WITH MINIMAL ROUNDING ERRORS

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COMPUTING 1994年第4期52卷 355-369页

作者： KOBBELT, L 1. Institut für Betriebs-und Dialogsysteme Abteilung geometrische Datenverarbeitung Universit?t Karlsruhe D-76128 Karlsruhe Federal Republic of Germany

We present a new algorithm which computes dot-products of arbitrary length with minimal rounding errors, independent of the number of addends. The algorithm has an O(n) time and O(1) memory complexity and does not need extensions of the arithmetic kernel, i.e., usual floating-point operations. A slight modification yields an algorithm which computes the dot-product in machine precision. Due to its simplicity, the algorithm can easily be implemented in hardware.

关键词： (EXACT) COMPUTER ARITHMETIC numerical algorithms DOT-PRODUCT COMPUTATION SUMMATION

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Microstructure Effects in Aluminized Solid Rocket Propellants

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JOURNAL OF PROPULSION AND POWER 2010年第4期26卷 724-733页

作者： De Luca, L. T. Galfetti, L. Colombo, G. Maggi, F. Bandera, A. Babuk, V. A. Sinditskii, V. P. Politecn Milan I-20156 Milan Italy Balt State Tech Univ St Petersburg 190005 Russia Mendeleev Univ Chem Technol Moscow 125047 Russia

Experiments concerning the ballistic characterization of several nanoaluminum (nAl) powders are reported. Most studies were performed with laboratory composite solid rocket propellants based on ammonium perchlorate as oxidizer and hydroxyl-terminated polybutadiene as inert binder. The ultimate objective is to understand the flame structure of differently metallized formulations and improve their specific impulse efficiency by mitigating the two-phase losses. Ballistic results confirm, for increasing nAl mass fraction or decreasing nAl size, higher steady burning rates with essentially the same pressure sensitivity and reduced average size of condensed combustion products. However, aggregation and agglomeration phenomena near the burning surface appear noticeably different for microaluminum (mu Al) and nAl powders. By contrasting the associated flame structures, a particle-laden flame zone with a sensibly reduced particle size is disclosed in the case of nAl. Propellant microstructure is considered the main controlling factor. A way to predict the incipient agglomerate size for mu Al propellants is proposed and verified by testing several additional ammonium perchlorate/hydroxyl-terminated polybutadiene/aluminum formulations of industrial manufacture.

关键词： High Energy Material Aluminized Composite Solid Propellant Propellant Storage Combustion Inefficiency Condensation Statistical Analysis Polypropylene Solid Rocket Motor Thermal Conductivity numerical algorithms

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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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Micromechanical modeling of coupled viscoelastic-viscoplastic composites based on an incrementally affine formulation

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INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES 2013年第10期50卷 1755-1769页

作者： Miled, B. Doghri, I. Brassart, L. Delannay, L. Catholic Univ Louvain IMMC B-1348 Louvain Belgium

This study proposes a micromechanical modeling of inclusion-reinforced viscoelastic-viscoplastic composites, based on mean-field approaches. For this, we have generalized the so-called incrementally affine linearization method which was proposed by Doghri et al. (2010a) for elasto-viscoplastic materials. The proposal provides an affine relation between stress and strain increments via an algorithmic tangent operator. In order to find the incrementally affine expression, we start by the linearization of evolution equations at the beginning of a time step around the end time of the step. Next, a numerical integration of the linearized equations is required using a fully implicit backward Euler scheme. The obtained algebraic equations lead to an incrementally affine formulation which is form-similar to linear thermoelasticity, therefore known homogenization models for linear thermoelastic composites can be applied. The proposed method can deal with general viscoelastic-viscoplastic constitutive models with an arbitrary number of internal variables. The semi-analytical predictions are validated against finite element simulations and experimental results. (C) 2013 Elsevier Ltd. All rights reserved.

关键词： Homogenization Viscoelasticity Viscoplasticity Linearization numerical algorithms Micromechanics

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Three-dimensional discrete element models for the granular statics and dynamics of powders in cavity filling

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JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS 2009年第1期57卷 10-31页

作者： Bierwisch, C. Kraft, T. Riedel, H. Moseler, M. Fraunhofer Inst Werkstoffmech IWM D-79108 Freiburg Germany

Rapid granular flow from a moving container and angle of repose formation were investigated by numerical simulations using the discrete element method (DEM) and experiments. Grain models of various geometrical complexity were studied and their ability to reproduce the experiments in those regimes was explored. The predictive power of the most realistic model for gravity driven cavity filling was assessed. Good agreement between computed and measured density distributions within the filled cavities provides a basis for numerical process variations aiming at homogenized density distributions. The effect of numerical coarse graining was found to be negligible for all properties of interest provided that force laws are scaled properly and corrections for boundary effects are taken into account. The proposed scaling was tested for a certain set of force laws but could be applied to different DEM forces as well. An analytic mass flow law for powder discharge from a moving container was derived and verified by our DEM simulations. (C) 2008 Elsevier Ltd. All rights reserved.

关键词： Dynamics Granular material Contact mechanics numerical algorithms Cavity filling

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Third-order, minimal-parameter solution of the orthogonal matrix differential equation

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1997年第3期20卷 516-521页

作者： Ronen, M Oshman, Y Technion—Israel Institute of Technology Haifa 32000 Israel

The problem of minimal-parameter solution of the orthogonal matrix differential equation is addressed. This well-known equation arises naturally in three-dimensional attitude determination problems (in aircraft and satellite navigation systems), as well as in the square-root solution of the matrix Riccati differential equation. A direct solution of this equation involves n(2) integrations for the elements of the nth-order solution matrix. However, since an orthogonal matrix is determined by only n(n - 1)/2 independent (albeit nonunique) parameters, a much more efficient solution may, conceivably, be obtained by a parametrization of the problem in terms of such parameters. A new, third-order minimal parametrization, which is motivated by the Peano-Baker solution of linear matrix differential equations, is introduced. The parameters and their corresponding differential equation are very simple and natural. The proposed method is used to provide a new derivation of a closed-form third-order quaternion propagation algorithm, which is commonly used in strapdown inertial navigation systems utilizing rate-integrating gyros. A numerical example is used to demonstrate the viability and high efficiency of the new algorithm.

关键词： Differential Equations Quaternions Strapdown Inertial Navigation System Satellite Navigation Systems Euler Angles Runge Kutta Integration Integration Algorithm Riccati Equations FORTRAN numerical algorithms

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