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3 2007

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Symulacyjny pakiet do badania bezpieczeństwa ruchu pojazdu szynowego

Opala M.

Prace Naukowe Politechniki Warszawskiej. Transport

2007

z. 62

235-242

W artykule przedstawiono sposób oceny bezpieczeństwa ruchu pojazdów szynowych przy pomocy metod symulacji komputerowej. Podane zostały kryteria stosowane w badaniach homologacyjnych w warunkach rzeczywistych oraz ich zastosowanie dla potrzeb badań symulacyjnych.

The article presents a concept of computer simulation-aided running safety assessmrnt of railwey vehicles. Given are the criteria used used in Poland when homologation of railway vehicles is conducted in real conditions and the application of these criteria to the needs of computer simulation analysis.

Object library of algorithms for dynamic optimization problems; Benchmarking SQP and nonlinear interior point methods

Błaszczyk J., Karbowski A., Malinowski K.

International Journal of Applied Mathematics and Computer Science

2007

Vol. 17, no 4

515-537

The main purpose of this paper is to describe the design, implementation and possibilities of our object-oriented library of algorithms for dynamic optimization problems. We briefly present library classes for the formulation and manipulation of dynamic optimization problems, and give a general survey of solver classes for unconstrained and constrained optimization. We also demonstrate methods of derivative evaluation that we used, in particular automatic differentiation. Further, we briefly formulate and characterize the class of problems solved by our optimization classes. The solution of dynamic optimization problems with general constraints is performed by transformation into structured large-scale nonlinear programming problems and applying methods for nonlinear optimization. Two main algorithms of solvers for constrained dynamic optimization are presented in detail: the sequential quadratic programming (SQP) exploring the multistage structure of the dynamic optimization problem during the solution of a sequence of quadratic subproblems, and the nonlinear interior-point method implemented in a general-purpose large-scale optimizer IPOPT. At the end, we include a typical numerical example of the application of the constrained solvers to a large-scale discrete-time optimal control problem and we use the performance profiles methodology to compare the efficiency and robustness of different solvers or different options of the same solver. In conclusions, we summarize our experience gathered during the library development.

Automatic differentiation in mechanical simulation using Matlab

Opala M., Żochowski A.

Archives of Transport

2007

Vol. 19, iss. 1-2

147-156

The objective of this article is to present an application of automatic differentiation in modeling of dynamic systems in Matlab software environment. Beside the theoretical description there are also examples for two different systems. The first of the two is a physical triple pendulum in vertical pIane with supplied source code used for computation. The other one is a real world example comprising a model of a railway vehicle with 27 degrees of freedom.

Artykuł prezentuje zastosowanie automatycznego różniczkowania w modelowaniu układów dynamicznych z wykorzystaniem pakietu Matlab. Przedstawiono przykłady wraz z kodem źródłowym, a także wyniki obliczeń dla modelu pojazdu szynowego o 27 stopniach swobody.