Andreas Varga

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An overview of numerically reliable algorithms for model reduction is presented. The covered topics are the reduction of stable and unstable linear systems as well as the computational aspects of frequency weighted model reduction. The presentation of available software tools focuses on a recently developed Fortran library RASP-MODRED implementing a new(More)
The recently developed PERIODIC SYSTEMS Toolbox for MATLAB is described. The basic approach to develop this toolbox was to exploit the powerful object manipulation features of MATLAB via flexible and functionally rich high level m-functions, while simultaneously enforcing highly efficient and numerically sound computations via the mex-function technology of(More)
We describe the model reduction software developed recently for the control and systems library SLICOT. Besides a powerful collection of Fortran 77 routines implementing the last algorithmic developments for several well-known balancing related methods, we also describe model reduction tools developed to facilitate the usage of SLICOT routines in user(More)
Kronecker-like forms of a system pencil are useful in solving many computational problems encountered in the analysis and synthesis of linear systems. The reduction of system pencils to various Kronecker-like forms can be performed by structure preserving 0(n 3) complexity numerically stable algorithms. The presented algorithms form the basis of a modular(More)
We propose a general method based on the balanced stochastic truncation (BST) approach for the model reduction of stable linear systems. The new method relies on a recent general inner-outer factorization result and extends the applicability of the BST method to systems with infinite zeros. A computational algorithm with enhanced accuracy for the new BST(More)
The efficient solution of a class of controller approximation problems by using frequency-weighted balancing related model reduction approaches is considered. It is shown that for certain standard performance and stability enforcing frequency-weights, the computation of the frequency-weighted controllability and observability grammians can be done by(More)
The general applicability of the modal approach for model reduction is restricted by the lack of guaranteed bounds for approximation errors and the lack of a satisfactory modal dominance analysis procedure. Functional and computational enhancements of this approach are proposed. Functional enhancements arise by combining the modal techniques with other(More)
A computer assisted modelling methodology is developed for the generation of linearized models with parametric uncertainties described by Linear Fractional Transformations (LFTs). The starting point of the uncertainty modelling is a class of generic nonlinear aircraft models with explicit parametric dependence used for simulation purposes. The proposed(More)
In this paper we describe a computational approach to the optimal output feedback control of multi-model systems by means of a unique constant output feedback matrix. Extension of the method to output feedback control of multi-model periodic systems is also presented. The power of the proposed approach is illustrated by the simultaneous stabilization and(More)