Control and Cybernetics

Items from 1 to 20 out of 1,014 results

article

Legendre polynomials method in time-optimal control of linear single-input

J. Pełczewski

Control and Cybernetics > 1998 > Vol. 27, no 1 > 105-117

The paper deals with application of shifted Legendre polynomials in the time-optimal control problem for a linear, time invariant, undisturbed, single-input system. It was assumed that the normality condition of the time-optimal control is satisfied, the state matrix is nonsingular, and all its eigenvalues are real nonpositive. The method of evaluating the approximate swiching instants of the bang-bang...

article

Construction of a k-immunization strategy with the highest convexity

L. Zaremba

Control and Cybernetics > 1998 > Vol. 27, no 1 > 135-144

Assuming that interest rate shocks are proportional to their values plus one, we prove in Theorem 1 the existence of and construct a portfolio Z[sup *] with the highest convexity in the class of portfolios that solve the immunization problem to meet the liability to pay C dollars K years from now. Z[sup *] appears to be a barbell strategy with two zero-coupon bonds with the shorest and the longest...

article

Discrete-time Markovian jump linear systems

K. Szajowski, W. Koning

Control and Cybernetics > 1998 > Vol. 27, no 1 > 63-80

The paper considers a problem of optimal control of a linear system with the parameters dependent on the states of a Markov chain. The cost criterion is quadratic in the controls and states of the system. The criterion parameters also depend on the states of the Markov chain. Two models of observation of the Markov chain are adopted - delay for one step and no delay. It is shown that under appopriate...

article

Memoryless equilibrium strategies in multilevel decision processes of discrete-time descriptor systems

H. Xu, K. Mizukami, M. Kobara

Control and Cybernetics > 1998 > Vol. 27, no 1 > 81-103

Applying a general theorem developed by Basar (1981), providing a set of sufficient conditions for a triple of strategies to be in hierarchical equilibrium, to games in normal (strategic) form, we study three-player Stackelberg games for linear quadratic discrete-time descriptor systems with three levels of hierarchy in decision making. We derive explicitly sufficient conditions for the existence...

article

Discrete approximation of nonconvex hyperbolic optimal control problems with state constraints

I. Chryssoverghi, A. Bacopoulos, J. Coletsos, B. Kokkinis

Control and Cybernetics > 1998 > Vol. 27, no 1 > 29-50

We consider an opitmal control problem for systems defined by nonlinear hyperbolic partial differential equations with state constraints. Since no convexity assumptions are made on the data, we also consider the control problem in relaxed form. We discretize both the classical and the relaxed problenms by using a finite element method in space and a finite difference scheme in time, the controls being...

article

Regularized penalty method for non-coercive parabolic optimal control problems

A. Kaplan, R. Tichatschke

Control and Cybernetics > 1998 > Vol. 27, no 1 > 5-27

The application of a proximal point approach to illposed convex control problems governed by linear parabolic equations is studied. A stable penalty method is constructed by means of multi-step proximal regularization (only w.r.t. the control functions) in the penalized problems. For distributed control problems with state constraints convergence of the approximately determined solutions of the regularized...

article

Necessary optimality conditions for nonsmooth two-dimensional control systems described by Roesser's model

M. Studniarski

Control and Cybernetics > 1998 > Vol. 27, no 1 > 51-61

Necessary optimality conditions for nonlinear nonsmooth two-dimensional discrete control systems are derived. Under additional convexity assumptions, these conditions can be obtained in the form of a maximum principle. For some special cases, sufficient optimality conditions are also presented.

article

A stability based neural networks controller design method

J. Song, X. Xu, X. He

Control and Cybernetics > 1998 > Vol. 27, no 1 > 119-133

The use of neural networks in control systems can be seen as a natural step in the evolution of control methodology to meet new challenges. Many attempts have been made to apply the neural networks to deal with non-linearities and uncertainties of the control systems. Research in neural network applications to control can be classified according to the major methods depending on structures of the...

article

On existence of energy minimizing configurations for mixtures of two imperfectly bonded conductors

R. Lipton

Control and Cybernetics > 1998 > Vol. 27, no 2 > 217-234

We consider a domain filled with a suspension of heat conducting spheres of conductivity sigma[sub p] embedded in a matrix of lesser conductivity sigma[sub m]. It is assumed that there exists a thermal contact resistance at the sphere - matrix interface.The contact resistance is characterized by a scalar Beta, which has dimensions of conductivity per unit lenght. A current flux is prescribed on the...

article

G-closures of material sets in space-time and perspectives of dynamic control in the coefficients of linear hyperbolic equations

K. Lurie

Control and Cybernetics > 1998 > Vol. 27, no 2 > 283-294

The paper is focused on the conept of material mixing in dynamics. This concept introduces the spatio-temporal composites, i.e. material microstructures assembled and maintained in space-time. The knowledge of the relevant sets of effective material parameters (G-closures) is crucial for the purpose of material optimization arising in dynamics of moving media, particularly acoustics and hydroacoustics,...

article

Mixed finite element formulation and optimal design of thin composite laminates

C. Cinquini, C. Mariani, P. Venini

Control and Cybernetics > 1998 > Vol. 27, no 2 > 165-176

A Hellinger-Reissner variational principle is introduced to derive the weak form equation of thin generally orthotropic laminates. It leads naturally to a mixed finite-element approximation that has the out-of-plane deflection and the bending and twisting moments as independent unknowns. A triangular element is derived that is used for both analysis and optimization purposes. Numerical simulations...

article

A formulation for optimal continuum structures with a decomposition of material properties into specified and designable parts

M. Bendsoe, J. Taylor, P. Washabaugh

Control and Cybernetics > 1998 > Vol. 27, no 2 > 255-264

A formulation is presented for optimal design in the setting of linear elastostatics for continuum structures, where the modulus tensor field is expressed as a decomposition into a set of independent tensors. For the linear case at hand, net material properties simply equal the sum of the constituent tensor fields. The design variables are comprised of one or more of the these fields, while the remaining...

article

Constitutive parameters and their evolution

P. Pedersen, D. Tortorelli

Control and Cybernetics > 1998 > Vol. 27, no 2 > 295--310

The three-dimensional problem of anisotropic evolution is formulated and solved using the tools from optimal design. Basic assumptions are the principle of maximum energy dissipation and a function that relates the damage, as measured by the rate of a constitutive matrix norm, to an effective stress measure. The presentation relies on alternative description for the 21 constitutive parameters and...

article

On solvability of boundary value problems in elastoplasticity

A. Chludnev, J. Sokołowski

Control and Cybernetics > 1998 > Vol. 27, no 2 > 311-330

In the paper the existence of a solution to the thress-dimensional elastoplastic problem with the Prandtl-Reuss constitutive law and the Neumann boundary conditions is established. The proof is based on a suitable combination of the parabolic regularization of equations and the penalty method for the elastoplastic yield condition. The method is applied in the case of the domain with smooth boundary...

article

Stable optimal design of two-dimensional elastic structures

A. Cerkaev, L. Krog, I. Kucuk

Control and Cybernetics > 1998 > Vol. 27, no 2 > 265-282

We study optimal layout of piece-wise periodic structures of linearly elastic materials. The effective tensors of these structures are constant within pre-specified regions, the optimality is understood as the minimum of complementary energy. The suggested formulation leads to a construction that is stable under variation of the loading and which does not degenerates into checkerboard type structures...

article

Structural optimization with a non-smooth buckling load criterion

J. Folgado, H. Rodrigues

Control and Cybernetics > 1998 > Vol. 27, no 2 > 235-253

This work addresses problems in optimal design of structures with a non-smooth buckling load criterion and in particular appliactions in layout design of plate reinforcements using a material based model and thickness beam optimization problems. Starting with the formulation of the linearized buckling problem, the optimization problem is formulated and the optimal necessary conditions are derived...

article

Shape optimization of a loudspeaker diaphragm with respect to soun directivity properties

S. Christensen, N. Olhoff

Control and Cybernetics > 1998 > Vol. 27, no 2 > 177-198

This paper presents a novel method for optimizing the directivity of the sound emission from the diaphragm of an electro dynamic loudspeaker. The analysis of the diaphragm is performed by finite element analysis of the structural dynamic behaviour and using the boundary element method for the acoustic analysis. Through optimization of a dead mass distribution on the diaphragm, or of the shape of the...

article

Some analytical properties of the multidimensional continuous Mróz model of plasticity

M. Brokate, P. Krejci, D. Rachinskij

Control and Cybernetics > 1998 > Vol. 27, no 2 > 199-215

We study the geometrical structure of memory induced by the continuous multidimensional Mróz model of plasticity. The results are used for proving the thermodynamic consistency of the model and composition and inversion formulas for input - memory state - output operators. We also show an example of nonuniqueness of solutions to a simple initial value problem involving the Mróz operator.

article

Contingent epiderivative and its applications to set-valued optimization

E. Bednarczuk, W. Song

Control and Cybernetics > 1998 > Vol. 27, no 3 > 375-386

In the present paper we give an alternative definition of contingent epiderivative for a set-valued map. We use our concept of contingent epiderivative to formulate necessary and/ or sufficient optimality conditions for a set-valued optimization problem and to study sensivity of a family of parametrized vector optimization problems.

article

A comparative study of the fuzzy linear model and the DEA in evaluation of efficiency of the DMUs

Y. Uemura

Control and Cybernetics > 1998 > Vol. 27, no 3 > 471-477

Evaluation of efficiency for every DMU (Decision Making Unit) in a company is a very important issue. Thus, the studies of evaluation of efficiency are being actively carried out on the basis of production functions. Until now, loglinear production function (Cobb-Douglas model) has been used for evaluation. This loglinear model evaluates DMUs by measuring the average. Recently, DEA (Data Envelopment...

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Control and Cybernetics

Legendre polynomials method in time-optimal control of linear single-input

Construction of a k-immunization strategy with the highest convexity

Discrete-time Markovian jump linear systems

Memoryless equilibrium strategies in multilevel decision processes of discrete-time descriptor systems

Discrete approximation of nonconvex hyperbolic optimal control problems with state constraints

Regularized penalty method for non-coercive parabolic optimal control problems

Necessary optimality conditions for nonsmooth two-dimensional control systems described by Roesser's model

A stability based neural networks controller design method

On existence of energy minimizing configurations for mixtures of two imperfectly bonded conductors

G-closures of material sets in space-time and perspectives of dynamic control in the coefficients of linear hyperbolic equations

Mixed finite element formulation and optimal design of thin composite laminates

A formulation for optimal continuum structures with a decomposition of material properties into specified and designable parts

Constitutive parameters and their evolution

On solvability of boundary value problems in elastoplasticity

Stable optimal design of two-dimensional elastic structures

Structural optimization with a non-smooth buckling load criterion

Shape optimization of a loudspeaker diaphragm with respect to soun directivity properties

Some analytical properties of the multidimensional continuous Mróz model of plasticity

Contingent epiderivative and its applications to set-valued optimization

A comparative study of the fuzzy linear model and the DEA in evaluation of efficiency of the DMUs

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