Florin Dan Barb

SPECFIT-an interactive package for Mössbauer spectra fitting with personal computers

Abstract SPECFIT is an interactive package that performs fitting of Mossbauer spectra on IBM-PC/AT compatible personal computers, SPECFIT implements a recently developed modified Gauss-Newton algorithm, includes a spectra calibration task and offers multiple graphical facilities. All functions are performed by means of a command language and predefined command sequences can be used.

Model reduction techniques for sampled-data systems

An “approximately” balanced realization of linear finite-dimensional sampled-data systems is proposed. The theoretical support of the “approximately” balancing algorithm is represented by a result on the asymptotic expansions with respect to the sampling step of the sampled controllability and observability graminas. Reduced order models obtained as singular perturbational approximations of “approximately” balanced realizations of sampled-data systems are shown to be acceptable solutions to the sampled-data system model reduction problem in the sense that, enjoying some asymptotic properties, they come “close” to the exact solutions as the sampling step decreases. An example illustrates the results.

On the Hankel singular values of linear continuous and sampled-data multivariable systems

Abstract This paper considers the Hankel singular values of the sample-data systems obtained from continuous-time models via standard sampling techniques. It is shown that the Hankel singular values of the sampled-data system recover the Hankel singular values of the continuous-time system as the sampling period approaches zero. A state space proof of this result is given.

Digital control of Pritchard-Salamon systems

Abstract In this paper we are concerned with the digital approach to the LQ optimal control problem of Pritchard-Salamon systems. We show how the digital control problem can be converted into an equivalent discrete-time LQ control problem and the construction of the optimal control law is based on the solution of classical Riccati equations.

The optimal projection equations for finite-dimensional fixed-order ℋ2-optimal control of infinite-dimensional discrete-time systems

In this paper we are concerned with the fixed, finite-order ℋ2-optimal control of linear, infinite-dimensional discrete-time systems. The set of necessary conditions for the existence of the ℋ2-optimal controller is expressed in terms of four operator equations (two modified Riccati equations and two modified Lyapunov equations) coupled by a projector having the rank given by the dimension of the compensator state. It is shown that, when the order of the compensator is equal to the order of the plant, the four operator equations are decoupled and we obtain the infinite-dimensional generalization of the finite-dimensional state-space solution to the ℋ2-optimal control problem for time-varying systems, as given by lonescu and Weiss (1992).

Digital H/sup /spl infin//-control with measurement-feedback for Pritchard-Salamon systems. II. A Popov theory based solution

In this second part of the paper the authors give a Popov theory based solution to the H/sup /spl infin//-suboptimal control problem.<<ETX>>

Digital H/sup /spl infin//-control with measurement-feedback for Pritchard-Salamon systems. I. The equivalent discrete-time control problem

In the first part of the paper the authors show how the hybrid control problem can be reduced into an equivalent discrete-time one. The main tool used is the so called lifting technique.<<ETX>>