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EN
This paper proposes a variance upper bound based interval Kalman filter that enhances the interval Kalman filter based on the same principle proposed by Tran et al. (2017) for uncertain discrete time linear models. The systems under consideration are subject to bounded parameter uncertainties not only in the state and observation matrices, but also in the covariance matrices of the Gaussian noises. By using the spectral decomposition of a symmetric matrix and by optimizing the gain matrix of the proposed filter, we lower the minimal upper bound on the state estimation error covariance for all admissible uncertainties. This paper contributes with an improved algorithm that provides a less conservative error covariance upper bound than the approach proposed by Tran et al. (2017). The state estimates are determined using interval analysis in order to enclose the set of all possible solutions of the classical Kalman filter consistent with the uncertainties.
EN
The paper concerns the properties of linear dynamical systems described by linear differential equations, excited by the Dirac delta function. A differential equation of the form an x(n) (t) + ∙∙∙ a1 x’(t) + a0 x(t) = bm u (t) + ∙∙∙ + b1 u’(t) + b0 u(t) is considered with ai, bj >0. In the paper we assume that the polynomials Mn(s) = ansn + ∙∙∙ + a1s + a0 and Lm(s) = bmsm + ∙∙∙ + b1s + b0 partly interlace. The solution of the above equation is denoted by x(t, Lm, Mn). It is proved that the function x(t, Lm, Mn) is nonnegative for t ∊ (0, ∞) , and does not have more than one local extremum in the interval (0, ∞) (Theorems 1, 3 and 4). Besides, certain relationships are proved which occur between local extrema of the function x(t, Lm, Mn), depending on the degree of the polynomial Mn(s) or Lm(s) (Theorems 5 and 6).
EN
In the paper, the exact state observers will be presented. The state estimators and observers can be used in technical processes for many purposes like the fault detection and diagnosis, the implementation of the state controllers, and soft reconstruction of inaccessible for measurements variables of the system. As the standard, for continuous systems the differential estimators of Kalman filter or Luenberger type observer are commonly used. However, if the initial conditions of the real state are unknown, both estimators guarantee only an asymptotic quality of the real state tracking. The paper presents another type of the state observers, which for continuous system have the structure given by two integral operators. Based on measurements of the system input and output signals on some predefined finite time interval T, they can reconstruct the initial state exactly. In on-line version, the exact state reconstruction is performed continuously for every t, based on special procedure executed within two moving windows of width T, on sliding time interval [t-T, t].
EN
The aim of this paper is to investigate dense linear algebra algorithms on shared memory multicore architectures. The design and implementation of a parallel tiled WZ factorization algorithm which can fully exploit such architectures are presented. Three parallel implementations of the algorithm are studied. The first one relies only on exploiting multithreaded BLAS (basic linear algebra subprograms) operations. The second implementation, except for BLAS operations, employs the OpenMP standard to use the loop-level parallelism. The third implementation, except for BLAS operations, employs the OpenMP task directive with the depend clause. We report the computational performance and the speedup of the parallel tiled WZ factorization algorithm on shared memory multicore architectures for dense square diagonally dominant matrices. Then we compare our parallel implementations with the respective LU factorization from a vendor implemented LAPACK library. We also analyze the numerical accuracy. Two of our implementations can be achieved with near maximal theoretical speedup implied by Amdahl’s law.
EN
This paper proposes a new method for the analysis of continuous and periodic event-based state-feedback plus static feedforward controllers that regulate linear time invariant systems with time delays. Measurable disturbances are used in both the control law and triggering condition to provide better disturbance attenuation. Asymptotic stability and L2-gain disturbance rejection problems are addressed by means of Lyapunov–Krasovskii functionals, leading to performance conditions that are expressed in terms of linear matrix inequalities. The proposed controller offers better disturbance rejection and a reduction in the number of transmissions with respect to other robust event-triggered controllers in the literature.
6
Content available remote Normal positive linear systems and electrical circuits
EN
The notion of normal positive electrical circuits is introduced and some their specific properties are investigated. New state matrices of positive linear systems and electrical circuits are proposed and their properties are analyzed. It is shown that positive electrical circuits with diagonal state matrices are normal for all values of resistances, inductances and capacitances.
PL
W artykule zaproponowano pojęcie dodatniego obwodu elektrycznego oraz przeanalizowano specjalne własności dodatnich układów i obwodów elektrycznych. Wykazano, że dodatnie obwody elektryczne z diagonalnymi macierzami stanu są zawsze normalne dla wszystkich wartości rezystancji, indukcyjności i pojemności.
EN
State estimation of stochastic discrete-time linear systems subject to unknown inputs has been widely studied, but few works take into account disturbances switching between unknown inputs and constant biases. We show that such disturbances affect a networked control system subject to deception attacks on the control signals transmitted by the controller to the plant via unreliable networks. This paper proposes to estimate the switching disturbance from an augmented state version of the intermittent unknown input Kalman filter. The sufficient stochastic stability conditions of the obtained filter are established when the arrival binary sequence of data losses follows a Bernoulli random process.
EN
The aim of this work is to show that interval positive fractional discrete-time linear systems are asymptotically stable if and only if the respective lower and upper bound systems are asymptotically stable. The classical Kharitonov theorem is extended to interval positive fractional linear systems.
EN
A method for decentralized stabilization of fractional positive descriptor linear systems is proposed. Necessary and sufficient conditions for decentralized stabilization of fractional positive descriptor linear systems are established. The efficiency of the proposed method is demonstrated on a numerical example.
EN
This paper presents a novel approach to the design of fuzzy state feedback controllers for continuous-time non-linear systems with input saturation under persistent perturbations. It is assumed that all the states of the Takagi–Sugeno (TS) fuzzy model representing a non-linear system are measurable. Such controllers achieve bounded input bounded output (BIBO) stabilisation in closed loop based on the computation of inescapable ellipsoids. These ellipsoids are computed with linear matrix inequalities (LMIs) that guarantee stabilisation with input saturation and persistent perturbations. In particular, two kinds of inescapable ellipsoids are computed when solving a multiobjective optimization problem: the maximum volume inescapable ellipsoids contained inside the validity domain of the TS fuzzy model and the smallest inescapable ellipsoids which guarantee a minimum *-norm (upper bound of the 1-norm) of the perturbed system. For every initial point contained in the maximum volume ellipsoid, the closed loop will enter the minimum *-norm ellipsoid after a finite time, and it will remain inside afterwards. Consequently, the designed controllers have a large domain of validity and ensure a small value for the 1-norm of closed loop.
EN
The responses of continuous-time and discrete-time linear systems with derivatives of their inputs are addressed. It is shown that the formulae for state vectors and outputs are also valid for their derivatives if the inputs and outputs and their derivatives of suitable order are zero for t = 0. Similar results are also shown for the discrete-time linear systems and for the fractional continuous-time and discrete-time linear systems.
PL
W artykule rozpatrywane są ciągłe układy i obwody elektryczne liniowe oraz dyskretne układy liniowe z pochodnymi (i odpowiednio różnicami) wymuszeń. Pokazano, że wzory określające pochodne wyjścia układów i wektorów stanu są również prawdziwe dla ich pochodnych jeżeli odpowiednie warunki początkowe i ich pochodnych są zerowe. Analogiczne wyniki zostały również wyprowadzone dla układów dyskretnych rzędów całkowitych i niecałkowitych.
EN
A method of a measurement of a linear system’s impulse response is presented. For a rectangular input signal ΣΔ undersampling of the system's output signal enables calculations of its impulse response. An algorithm of output signal's digital processing enabling a reduction of errors is described. A dependence of measurement's errors on the number of samples per period and relation between sampling and signal's frequencies was analyzed. Exemplary calculations were performed for two typical linear systems.
PL
Zaprezentowano metodę pomiaru odpowiedzi impulsowej układu liniowego wykorzystującą podpróbkowanie ΣΔ jego sygnału wyjściowego przy prostokątnym sygnale wejściowym. Przedstawiono algorytm przetwarzania sygnałów, umożliwiający redukcję błędów pomiarowych. Przeanalizowano zależność błędów od krotności podpróbkowania, liczby próbek oraz błędów częstotliwości na przykładzie 2 typowych układów liniowych.
EN
The Weierstrass–Kronecker theorem on the decomposition of the regular pencil is extended to fractional descriptor continuous-time linear systems described by the Caputo–Fabrizio derivative. A method for computing solutions of continuous-time systems is presented. Necessary and sufficient conditions for the positivity and stability of these systems are established. The discussion is illustrated with a numerical example.
14
EN
The problem of minimal-phase realization for continuous-time and discrete-time linear systems is addressed. Necessary and sufficient conditions for the existence of minimal-phase realizations for the linear systems are established. A procedure for computation of the realizations is proposed and illustrated by numerical examples.
PL
Pracy zaproponowano nową metodę wyznaczanie minimalno-fazowych realizacji dla dodatnich ciągłych i dyskretnych układów liniowych. Podano warunki konieczne i wystarczające na istnienie minimalno-fazowych realizacji dla tych klas układów liniowych. Podano procedurę wyznaczania tych realizacji minimalno-fazowych oraz zlustrowano efektywność tej procedury na przykładach liczbowych.
15
Content available remote Another Approach to the Fractional Order Derivatives
EN
This paper presents custom approach to the fractional order derivatives. It is proposed other opportunity to determine equation for fractional order derivatives calculation. All of the considerations are supported by the numerical examples that show the usefulness of certain properties of the fractional derivatives. In this article is made an attempt to answer the questions: What is the fractional derivative? When, where and why the fractional derivative should be used? Which one equation is appropriate for the fractional order derivative calculus?
PL
W artykule przedstawiono niestandardowe podejście do pochodnych niecałkowitego rzędu. Zaproponowana została możliwość definiowania dowolnych równań pozwalających na wyznaczenie pochodnych niecałkowitego rzędu. Teoria opisana w pracy została poparta przykładami, które pokazują użyteczność niektórych właściwości pochodnej niecałkowitego rzędu zdefiniowanej dowolnym równaniem. W artykule zrealizowana została próba odpowiedzi na pytania Czym jest pochodna niecałkowitego rzędu? Kiedy, gdzie i dlaczego pochodna niecałkowitego rzędu powinna być stosowana? Które równania do wyznaczania pochodnej niecałkowitego rzędu są poprawne?
EN
The minimum energy control problem for the positive time-varying linear systems is formulated and solved. Sufficient conditions for the existence of solution to the problem are established. A procedure for solving of the problem is proposed and illustrated by a numerical example.
EN
In the paper the problems of practical stability and asymptotic stability of fractional discrete-time linear scalar systems with one constant delay are addressed. Standard and positive systems are considered. New conditions for practical stability and for asymptotic stability are established.
PL
Rozpatrzono problem stabilności liniowych skalarnych układów dyskretnych niecałkowitego rzędu z jednym opóźnieniem zmiennych stanu. Wykorzystując metodę podziału D, podano granczne warunki konieczne i wystarczające praktycznej stabilności. Bazując na tych warunkach, sformułowano proste analityczne warunki wystarczające stabilności praktycznej oraz stabilności asymptotycznej. W przypadku układów dodatnich podano proste analityczne warunki konieczne i wystarczające stabilności praktycznej oraz stabilności asymptotycznej.
19
Content available Double fault distinguishability in linear systems
EN
This paper develops a new approach to double fault isolation in linear systems with the aid of directional residuals. The method of residual generation for computational as well as internal forms is applied. Isolation of double faults is based on the investigation of the coplanarity of the residual vector with the planes defined by the individual pairs of directional fault vectors. Additionally, the method of designing secondary residuals, which are structured and directional, is proposed. These transformations allow achieving various isolation properties. It is shown that double fault distinguishability can be improved by decomposing the observed residual vector along the response directions. The described methods are illustrated with a simple computational example.
EN
A new method of analysis of descriptor continuous-time and discrete-time linear systems with singular pencil is proposed. The method is based on transformation of singular pencil by the use of the shuffle algorithm. Conditions for transformation of the descriptor linear systems to equivalent standard linear systems are established.
PL
Podano nową metodę analizy deskryptowych liniowych układów ciągłych i dyskretnych z pękami singularnymi. Proponowana metoda jest oparta na redukcji deskryptowych układów o pękach singularnych do równoważnych układów standardowych za pomocą algorytmu przesuwania. Podano warunki istnienia tej redukcji oraz ilustrowano proponowaną metodę przykładem numerycznym.
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