Results 1 - 10 of 13

Real-time control under clock offsets between sensors and controllers

by Kunihisa Okano, Masashi Wakaiki, João P. Hespanha
"... This paper studies the impact of clock mismatches in spa-tially distributed real-time control systems. We consider a con guration in which sensor measurements are collected by one processor that transmits the measurements to another control/actuation processor through a network, but the two processo ..."
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This paper studies the impact of clock mismatches in spa-tially distributed real-time control systems. We consider a con guration in which sensor measurements are collected by one processor that transmits the measurements to another control/actuation processor through a network, but the two processors do not have a common clock. Due to the clock mismatch, there will be an offset between the actual time at which a measurement is taken and the time reported by the sensor. Our goal is to discover fundamental limitations to the ability to stabilize the control loop arising from the clocks mismatch. We consider time-varying bounded offsets and derive limitations on the offset bound for the stability of the feedback system. For the case of a scalar linear process, there exists a critical limitation, which depends on the level of instability of the plant and the nominal sampling period. In contrast, for the vector linear processes, if the process dy-namics has at least two distinct real eigenvalues, then there is no fundamental limitation on the offset bound.
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Synchronization of Phase-coupled Oscillators with Plastic Coupling Strength

by Andrey Gushchin, Enrique Mallada, Ao Tang
"... Abstract—In this article we study synchronization of systems of homogeneous phase-coupled oscillators with plastic coupling strengths and arbitrary underlying topology. The dynamics of a coupling strength between two oscillators is governed by the phase difference between these oscillators. We show ..."
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Abstract—In this article we study synchronization of systems of homogeneous phase-coupled oscillators with plastic coupling strengths and arbitrary underlying topology. The dynamics of a coupling strength between two oscillators is governed by the phase difference between these oscillators. We show that such systems are gradient and always achieve frequency synchroniza-tion. Moreover, for these systems we provide sufficient stability and instability conditions that are based on results from algebraic graph theory. For a special case when underlying topology is a tree, we formulate a criterion of stability for equilibria. Several examples are used to demonstrate variety of equilibria the system has, and to illustrate differences in behavior of systems with constant and plastic coupling strengths. I.

Synchronization of Heterogeneous Kuramoto Oscillators with Graphs of Diameter Two. arXiv preprint

by Andrey Gushchin , Enrique Mallada , Ao Tang , 2014
"... Abstract-We study synchronization of coupled Kuramoto oscillators with heterogeneous inherent frequencies and general underlying connectivity. We provide conditions on the coupling strength and the initial phases which guarantee the existence of a Positively Invariant Set (PIS) and lead to synchron ..."
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Abstract-We study synchronization of coupled Kuramoto oscillators with heterogeneous inherent frequencies and general underlying connectivity. We provide conditions on the coupling strength and the initial phases which guarantee the existence of a Positively Invariant Set (PIS) and lead to synchronization. Unlike previous works that focus only on analytical bounds, here we introduce an optimization approach to provide a computational-analytical bound that can further exploit the particular features of each individual system such as topology and frequency distribution. Examples are provided to illustrate our results as well as the improvement over previous existing bounds.
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under a Creative Commons Attribution

by Alex Arenas
"... Control of coupled oscillator networks with application to microgrid technologies ..."
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Control of coupled oscillator networks with application to microgrid technologies
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f n i, r

by unknown authors
"... specific correlation with note that our method tor networks, provided rm. Moreover, because s have served as a para-nchronization in various hed light more generally d could potentially give he termination of cardiac We consider the famous Kuramoto m ..."
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specific correlation with note that our method tor networks, provided rm. Moreover, because s have served as a para-nchronization in various hed light more generally d could potentially give he termination of cardiac We consider the famous Kuramoto m
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Synchronization of nonlinear circuits in dynamic electrical networks

by Florian Dörfler, Sairaj V. Dhople, Brian B. Johnson, Abdullah Hamadeh - IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS I: REGULAR PAPERS , 2013
"... Synchronization of coupled oscillators is a pervasive theme of multi-disciplinary research. Focused on circuit-theoretic applications, in this paper, we derive sufficient conditions for global asymptotic synchronization in a system of identical nonlinear circuits coupled through linear time-invari ..."
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Synchronization of coupled oscillators is a pervasive theme of multi-disciplinary research. Focused on circuit-theoretic applications, in this paper, we derive sufficient conditions for global asymptotic synchronization in a system of identical nonlinear circuits coupled through linear time-invariant (LTI) electrical networks. The nonlinear circuits are composed of a parallel combination of passive LTI circuit elements and a nonlinear voltage-dependent current source with finite gain. The terminals of the nonlinear circuits are coupled through LTI networks characterized by either identical per-unit-length impedances or identical effective impedances between any two terminals. This setup is motivated by a recently proposed control strategy for inverters in microgrids. We analyze synchronization by means of an input-output analysis of a coordinate-transformed system that emphasizes signal differences. To apply the synchronization analysis to a broad class of networks, we leverage recent results on Kron reduction—a circuit reduction and transformation procedure that reveals the interactions of the nonlinear circuits. We illustrate our results with simulations in networks of coupled Chua’s circuits.

RESEARCH ARTICLE Timescales of Massive Human Entrainment

by Riccardo Fusaroli, Marcus Perlman, Alan Mislove, Ra Paxton, Teenie Matlock, Rick Dale
"... The past two decades have seen an upsurge of interest in the collective behaviors of com-plex systems composed of many agents entrained to each other and to external events. In this paper, we extend the concept of entrainment to the dynamics of human collective atten-tion. We conducted a detailed in ..."
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The past two decades have seen an upsurge of interest in the collective behaviors of com-plex systems composed of many agents entrained to each other and to external events. In this paper, we extend the concept of entrainment to the dynamics of human collective atten-tion. We conducted a detailed investigation of the unfolding of human entrainment—as ex-pressed by the content and patterns of hundreds of thousands of messages on Twitter— during the 2012 US presidential debates. By time-locking these data sources, we quantify the impact of the unfolding debate on human attention at three time scales. We show that collective social behavior covaries second-by-second to the interactional dynamics of the debates: A candidate speaking induces rapid increases in mentions of his name on social media and decreases in mentions of the other candidate. Moreover, interruptions by an in-terlocutor increase the attention received. We also highlight a distinct time scale for the im-pact of salient content during the debates: Across well-known remarks in each debate, mentions in social media start within 5–10 seconds after it occurs; peak at approximately one minute; and slowly decay in a consistent fashion across well-known events during the debates. Finally, we show that public attention after an initial burst slowly decays through the course of the debates. Thus we demonstrate that large-scale human entrainment may hold across a number of distinct scales, in an exquisitely time-locked fashion. The methods and results pave the way for careful study of the dynamics and mechanisms of large-scale human entrainment.
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f n i, r

by unknown authors
"... specific correlation with note that our method tor networks, provided rm. Moreover, because s have served as a para-nchronization in various hed light more generally d could potentially give he termination of cardiac We consider the famous Kuramoto m ..."
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specific correlation with note that our method tor networks, provided rm. Moreover, because s have served as a para-nchronization in various hed light more generally d could potentially give he termination of cardiac We consider the famous Kuramoto m
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1Distributed Synchronization of Heterogeneous Oscillators on Networks with Arbitrary Topology

by Enrique Mallada, Y A. Freeman, Ao Tang
"... Many network applications rely on the synchronization of coupled oscillators. For example, such syn-chronization can provide networked devices with a common temporal reference necessary for coordinating actions or decoding transmitted messages. In this paper, we study the problem of using distribute ..."
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Many network applications rely on the synchronization of coupled oscillators. For example, such syn-chronization can provide networked devices with a common temporal reference necessary for coordinating actions or decoding transmitted messages. In this paper, we study the problem of using distributed control to achieve both phase and frequency synchronization of a network of coupled heterogeneous nonlinear os-cillators. Not only do our controllers guarantee zero phase error in steady state under arbitrary frequency heterogeneity, but they also require little knowledge of the oscillator nonlinearities and network topology. Furthermore, we provide a global convergence analysis, in the absence of noise and propagation delay, for the resulting nonlinear system whose phase vector evolves on the n-torus.
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Construction of power flow feasibility sets

by Krishnamurthy Dvijotham, Konstantin Turitsyn
"... Abstract—We develop a new approach for construction of convex analytically simple regions where the AC power flow equa-tions are guaranteed to have a feasible solutions. Construction of these regions is based on efficient semidefinite programming techniques accelerated via sparsity exploiting algori ..."
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Abstract—We develop a new approach for construction of convex analytically simple regions where the AC power flow equa-tions are guaranteed to have a feasible solutions. Construction of these regions is based on efficient semidefinite programming techniques accelerated via sparsity exploiting algorithms. Result-ing regions have a simple geometric shape in the space of power injections (polytope or ellipsoid) and can be efficiently used for assessment of system security in the presence of uncertainty. Efficiency and tightness of the approach is validated on a number of test networks. I.
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