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EN
Consider the semilinear system defined by {x(i+1)=Ax(i)+f(x(i)), i≥0 x(0)=x0∈Rn and the corresponding output signal y(i)=C x(i), i≥0, where A is a n×n matrix, C is a p x n matrix and f is a nonlinear function. An initial state x(0) is output admissible with respect to A, f, C and a constraint set Ω ⊂ Rp, if the output signal (y(i)i associated to our system satisfies the condition y(i) ∈ Ω, for every integer i≥0. The set of all possible such initial conditions is the maximal output admissible set Γ(Ω). In this paper we will define a new set that characterizes the maximal output set in various systems(controlled and uncontrolled systems) .Therefore, we propose an algorithmic approach that permits to verify if such set is finitely determined or not. The case of discrete delayed systems is taken into consideration as well. To illustrate our work, we give various numerical simulations.
EN
In this paper we study the existence of solutions of a nonlinear quadratic integral equation of fractional order. This equation is considered in the Banach space of real functions defined, continuous and bounded on the real half axis. Additionally, using the technique of measures of noncompactness we obtain some characterization of considered integral equation. We provide also an example illustrating the applicability of our approach.
3
Content available Stabilization of discrete-time LTI positive systems
EN
The paper mitigates the existing conditions reported in the previous literature for control design of discrete-time linear positive systems. Incorporating an associated structure of linear matrix inequalities, combined with the Lyapunov inequality guaranteing asymptotic stability of discrete-time positive system structures, new conditions are presented with which the state-feedback controllers and the system state observers can be designed. Associated solutions of the proposed design conditions are illustrated by numerical illustrative examples.
EN
This paper considers the problem of assessment of stability margin of linear periodically-time-variable circuits, in particular parametric amplifiers, which was investigated using the frequency symbolic method. The assessment of circuit stability is carried out by the real parts of the denominator roots of a normal parametric transfer function, which is defined by the frequency symbolic method in the form of the approximation of Fourier polynomials. The calculation is performed in an MATLAB environment.
PL
Praca przedstawia problem oceny marginesu stabilności obwodów liniowych, zmiennych w czasie. Rozważania dotyczą w szczególności wzmacniacza parametrycznego, analizowanego przy użyciu metody symbolicznej w dziedzinie częstotliwości. Stabilność jest określana na podstawie części rzeczywistej biegunów transmitancji obwodu parametrycznego, zdefiniowanej przy użyciu aproksymacji wielomianami Fouriera. Obliczenia numeryczne zostały wykonane przy zastosowaniu programu Matlab.
EN
The stability problem of continuous-time linear fractional order systems with state delay is considered. New simple necessary and sufficient conditions for the asymptotic stability are established. The conditions are given in terms of eigenvalues of the state matrix and time delay. It is shown that in the complex plane there exists such a region that location in this region of all eigenvalues of the state matrix multiplied by delay in power equal to the fractional order is necessary and sufficient for the asymptotic stability. Parametric description of boundary of this region is derived and simple new analytic necessary and sufficient conditions for the stability are given. Moreover, it is shown that the stability of the fractional order system without delay is necessary for the stability of this system with delay. The considerations are illustrated by a numerical example.
EN
In this paper, the stability problem of Furuta pendulum controlled by the fractional order PD controller is presented. A mathematical model of rotational inverted pendulum is derived and the fractional order PD controller is introduced in order to stabilize the same. The problem of asymptotic stability of a closed loop system is solved using the D-decomposition approach. On the basis of this method, analytical forms expressing the boundaries of stability regions in the parameters space have been determined. The D-decomposition method is investigated for linear fractional order systems and for the case of linear parameter dependence. In addition, some results for the case of nonlinear parameter dependence are presented. An example is given and tests are made in order to confirm that stability domains have been well calculated. When the stability regions have been determined, tuning of the fractional order PD controller can be carried out.
EN
The positivity and asymptotic stability of the fractional discrete-time nonlinear systems are addressed. Necessary and sufficient conditions for the positivity and sufficient conditions for the asymptotic stability of the fractional nonlinear systems are established. The proposed stability tests are based on an extension of the Lyapunov method to the positive fractional nonlinear systems. The effectiveness of tests is demonstrated on examples.
EN
The stability problems of fractional discrete-time linear scalar systems described by the new model are considered. Using the classical D-partition method, the necessary and sufficient conditions for practical stability and asymptotic stability are given. The considerations are il-lustrated by numerical examples.
9
Content available remote Positivity and stability of discrete-time and continuous-time nonlinear systems
PL
Przedstawione zostaną dodatnie i stabilne asymptotycznie nieliniowe układy dyskretne i ciągłe. Podane zostaną warunki wystarczające dodatniości i stabilności asymptotycznej układów nieliniowych. Proponowane metody badania stabilności zostaną oparte na uogólnieniu metody Lyapunova. Efektywność testów zostanie zademonstrowana na przykładach numerycznych.
EN
The positivity and asymptotic stability of the discrete-time and continuous-time nonlinear systems are addressed. Sufficient conditions for the positivity and asymptotic stability of the nonlinear systems are established. The proposed stability tests are based on an extension of the Lyapunov method to the positive nonlinear systems. The effectiveness of the tests are demonstrated on examples.
EN
Necessary and sufficient conditions for the positivity of time-varying fractional discrete-time linear systems are established. The problem of asymptotic stability of the positive time-varying fractional discrete-time linear systems is analyzed and sufficient conditions are given. Considerations are illustrated by numerical examples.
EN
The positivity and asymptotic stability of the descriptor linear continuous-time and discrete-time systems with regular pencils are addressed. Necessary and sufficient conditions for the positivity and asymptotic stability of the systems are established using the Drazin inverse matrix approach. Effectiveness of the conditions are demonstrated on numerical examples.
EN
In the paper the problem of stability of fractional discrete-time linear scalar systems with state space pure delay is considered. Using the classical D-decomposition method, the necessary and sufficient condition for practical stability as well as the sufficient condition for asymptotic stability are given.
PL
W pracy rozpatrzono problem stabilności liniowych skalarnych układów dyskretnych niecałkowitego rzędu z czystym opóźnieniem zmiennych stanu. Wykorzystując metodę podziału D podano warunek konieczny i wystarczający praktycznej stabilności oraz warunek wystarczający stabilności asymptotycznej.
EN
Continuous-time positive systems, switching among p subsystems whose matrices differ by a rank one matrix, are introduced, and a complete characterization of the existence of a common linear copositive Lyapunov function for all the subsystems is provided. Also, for this class of systems it is proved that a well-known necessary condition for asymptotic stability, namely the fact that All convex combinations of the system matrices are Hurwitz, becomes equivalent to the generally weaker condition that the systems matrices are Hurwitz. In the special case of two-dimensional systems, this allows for drawing a complete characterization of asymptotic stability. Finally, the case when there are only two subsystems, possibly with commuting matrices, is investigated.
EN
The asymptotic stability of positive fractional switched continuous-time linear systems for any switching is addressed. Simple sufficient conditions for the asymptotic stability of the positive fractional systems are established. It is shown that the positive fractional switched systems are asymptotically stable for any switchings if the sum of entries of every column of the matrices of all subsystems is negative.
EN
The asymptotic stability of positive switched linear systems for any switchings is addressed. Simple sufficient conditions for the asymptotic stability of positive switched continuous-time and discrete-time linear systems are established. It is shown that the positive switched continuous-time (discrete-time) system is asymptotically stable for any switchings if the sum of entries of every column of the matrices of subsystems is negative (less than 1)
EN
In the paper the problems of practical stability and asymptotic stability of fractional discrete-time linear systems are addressed. Necessary and sufficient conditions for practical stability and for asymptotic stability are established. The conditions are given in terms of eigenvalues of the state matrix of the system. In particular, it is shown that (similarly as in the case of fractional continuous-time linear systems) in the complex plane exists such a region, that location of all eigenvalues of the state matrix in this region is necessary and sufficient for asymptotic stability. The parametric description of boundary of this region is given. Moreover, it is shown that Schur stability of the state matrix (all eigenvalues have absolute values less than 1) is not necessary nor sufficient for asymptotic stability of the fractional discrete-time system. The considerations are illustrated by numerical examples.
EN
The paper focuses on a linear diffrence equation depending on parameters. The equation is related to Good win’s theory of extrapolative expectations. The stability region of the equation is investigated. Conditions for asymptotic stability are formulated and presented as an optimisation problem, which is further analysed. Despite employing state-of-the-art solvers, numerical results have turned out to be too ambiguous to provide the basis for definite conclusions about the investigated stability region.
EN
In the paper the problems of practical stability and asymptotic stability of fractional discrete-time linear systems with a diagonal state matrix are addressed. Standard and positive systems are considered. Simple necessary and sufficient analytic conditions for practical stability and for asymptotic stability are established. The considerations are illustrated by numerical examples.
EN
The paper concerns the problem of stabilization of continuous-time linear systems with distributed time delays. Using extended form of the Lyapunov-Krasovskii functional candidate, the controller design conditions are derived and formulated with respect to the incidence of structured matrix variables in the linear matrix inequality formulation. The result give sufficient condition for stabilization of the system with distributed time delays. It is illustrated with a numerical example to note reduced conservatism in the system structure.
EN
A new problem of asymptotic stability of positive continuous-time linear systems coupled by mutual state-feedbacks is formulated. It is shown that: 1) If one of the coupled systems is unstable then the closed-loop system is unstable for all gain matrices of the mutual state-feedbacks, 2) If at least one diagonal entry of the block diagonal matrices is positive then the closed-loop system is unstable for all gain matrices, 3) the possibility of modification of the dynamics of the closed-loop system by suitable choice of gain matrices is strongly limited. The considerations are illustrated by two examples.
PL
W pracy sformułowano i rozwiązano problem stabilności dodatnich liniowych układów ciągłych ze wzajemnym sprzężeniem zwrotnym. Wykazano, że 1) jeżeli jeden z układów jest niestabilny wtedy układ ze sprzężeniem zwrotnym jest niestabilny dla wszystkich wartości tych sprzężeń, 2) jeżeli przynajmniej jeden element na głównej przekątnej blokowych macierzy jest dodatni to układ ze sprzężeniem zwrotnym jest niestabilny dla wszystkich wartości tych sprzężeń, 3) możliwość modyfikacji dynamiki przez dobór sprzężeń zwrotnych jest silnie ograniczona. Rozwiązanie ogólne zilustrowano dwoma przykładami.
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