1,721,019 research outputs found
On multiconsensus of multi-agent systems under aperiodic and asynchronous sampling
Full text linkIn this paper, the problem of estimating a suitable bound for ensuring multiconsensus of single integrators under
asynchronous and aperiodical sampling is investigated. The estimate relies on a hybrid modeling of the network dynamics with a distributed time-delay acting over the connection. Simulations support the theoretical results
IDA-PBC for LTI dynamics under input delays: a reduction approach
Full text linkIn this paper, the problem of stabilizing linear port-controlled Hamiltonian dynamics through interconnection and damping assignment in presence of input delays is considered. The contribution exploits the reduction approach allowing to reveal and shape the energy properties of the time-delay dynamics. Performances are illustrated on a simple mechanical system
Stabilization of cascaded nonlinear systems under sampling and delays
Full text linkOver the last decades, the methodologies of dynamical systems and control theory have been playing an increasingly relevant role in a lot of situations of practical interest. Though, a lot of theoretical problem still remain unsolved. Among all, the ones concerning stability and stabilization are of paramount importance. In order to stabilize a physical (or not) system, it is necessary to acquire and interpret heterogeneous information on its behavior in order to correctly intervene on it. In general, those information are not available through a continuous flow but are provided in a synchronous or asynchronous way. This issue has to be unavoidably taken into account for the design of the control action. In a very natural way, all those heterogeneities define an hybrid system characterized by both continuous and discrete dynamics. This thesis is contextualized in this framework and aimed at proposing new methodologies for the stabilization of sampled-data nonlinear systems with focus toward the stabilization of cascade dynamics. In doing so, we shall propose a small number of tools for constructing sampled-data feedback laws stabilizing the origin of sampled-data nonlinear systems admitting cascade interconnection representations. To this end, we shall investigate on the effect of sampling on the properties of the continuous-time system while enhancing design procedures requiring no extra assumptions over the sampled-data equivalent model. Finally, we shall show the way sampling positively affects nonlinear retarded dynamics affected by a fixed and known time-delay over the input signal by enforcing on the implicit cascade representation the sampling process induces onto the retarded system
Lyapunov stabilization of discrete-time feedforward dynamics
Full text linkThe paper discusses stabilization of nonlinear discrete-time dynamics in feedforward form. First it is shown how to define a Lyapunov function for the uncontrolled dynamics via the construction of a suitable cross-term. Then, stabilization is achieved in terms of u-average passivity. Several constructive cases are analyzed
Teoria dei sistemi. Lineari stazionari a dimensione finita
Full text linkQuali sono i fondamenti teorici che sono alla base del comportamento dei sistemi complessi? Come comprendere e valutare le prestazioni di un sistema che si comporta in maniera autonoma?
La Teoria dei Sistemi ci dà gli strumenti per comprendere e ci introduce ai metodi di progetto nel sorprendente mondo dell'Automatica.
Dopo una breve introduzione destinata ad illustrare in modo succinto il punto di vista dell'Automatica, viene presentata la classe di modelli che sono oggetto di studio: si tratta delle rappresentazioni con lo stato lineari, stazionarie a dimensione finita, sia a tempo continuo che discreto. Lo studio nel dominio del tempo e della variabile complessa, sino alla caratterizzazione del comportamento in frequenza consente di mettere in evidenza i riscontri applicativi ai risultati teorici. Lo studio della stabilità interna ed esterna, delle proprietà dello spazio di stato, dei modelli dei sistemi interconnessi e delle loro proprietà in relazione a quelle dei componenti, sono i tasselli di un mosaico dei metodi fondamentali che vengono illustrati. La loro utilità nella valutazione delle prestazioni e nel progetto dei sistemi di controllo viene messa in luce nell'ultimo capitolo dove viene studiato il problema della modifica della dinamica con controreazione dall'uscita
Topology-induced containment for general linear systems on weakly connected digraphs
Full text linkThe paper deals with topology-induced containment output feedback for ensuring multi-consensus of homogeneous linear systems evolving over a weakly connected communication digraph. Starting from the extension of a recent characterization of multi-consensus, a decentralized static feedback enforcing multi-consensus is designed based on a suitable network-induced decomposition; a neighborhood state-observer is proposed for completing the design. The results are finally illustrated over a simple simulated example
Sampled-data stabilization of nonlinear dynamics with Input delays through immersion and invariance
Full text linkIn this technical note, we show that Immersion and Invariance is a natural framework for the design of sampled-data stabilizing controllers for input-delayed systems. Assuming the existence of a continuous-time feedback in the delay free case, Immersion and Invariance stabilizability of the equivalent sampled-data dynamics is proven. The proof is constructive for the stabilizing controller. Two simulated examples illustrate the performances
Feedforwarding under sampling
Full text linkThe paper deals with stabilization of feedforwardmultiple cascade dynamics under sampling. It is shown that u-average passivity concepts and Lyapunov methods can be profitably exploited to provide a systematic sampled-data design procedure. The proposed methodology recalls the continuous-time feedforwarding steps and can be applied under the same assumptions as those set over the continuous-time cascade dynamics. The final sampled feedback is carried out through a three steps procedure that involves iterative passivation and stabilization in the u-average sense. Constructive aspects are developed to compute approximate solutions which are indeed implemented in practice. An example is worked out with comparative simulations with respect to usual sampled-and-hold implementations
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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