| 1. |
- Adaldo, Antonio, et al.
(författare)
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Cloud-Supported Formation Control of Second-Order Multiagent Systems
- 2018
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Ingår i: IEEE Transactions on Control of Network Systems. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 2325-5870. ; 5:4, s. 1563-1574
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Tidskriftsartikel (refereegranskat)abstract
- This paper addresses a formation problem for a network of autonomous agents with second-order dynamics and bounded disturbances. Coordination is achieved by having the agents asynchronously upload (download) data to (from) a shared repository, rather than directly exchanging data with other agents. Well-posedness of the closed-loop system is demonstrated by showing that there exists a lower bound for the time interval between two consecutive agent accesses to the repository. Numerical simulations corroborate the theoretical results.
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| 2. |
- Adaldo, Antonio, 1989-, et al.
(författare)
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Event-Triggered Pinning Control of Switching Networks
- 2015
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Ingår i: IEEE Transactions on Control of Network Systems. - 2325-5870. ; 2:2, s. 204-213
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates event-triggered pinning control for the synchronization of complex networks of nonlinear dynamical systems. We consider networks described by time-varying weighted graphs and featuring generic linear interaction protocols. Sufficient conditions for the absence of Zeno behavior are derived and exponential convergence of a global normed error function is proven. Static networks are considered as a special case, wherein the existence of a lower bound for interevent times is also proven. Numerical examples demonstrate the effectiveness of the proposed control strategy.
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| 3. |
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| 4. |
- Andreasson, Martin, 1987-, et al.
(författare)
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Distributed controllers for multiterminal HVDC transmission systems
- 2017
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Ingår i: IEEE Transactions on Control of Network Systems. - : Institute of Electrical and Electronics Engineers (IEEE). - 2325-5870. ; 4:3, s. 564-574
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Tidskriftsartikel (refereegranskat)abstract
- High-voltage direct current (HVDC) is a commonly used technology for long-distance electric power transmission, mainly due to its low resistive losses. In this paper the voltagedroop method (VDM) is reviewed, and three novel distributed controllers for multi-terminal HVDC (MTDC) transmission systems are proposed. Sufficient conditions for when the proposed controllers render the closed-loop system asymptotically stable are provided. These conditions give insight into suitable controller architecture, e.g., that the communication graph should be identical with the graph of the MTDC system, including edge weights. Provided that the closed-loop systems are asymptotically stable, it is shown that the voltages asymptotically converge to within predefined bounds. Furthermore, a quadratic cost of the injected currents is asymptotically minimized. The proposed controllers are evaluated on a four-bus MTDC system.
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| 5. |
- Bjork, J., et al.
(författare)
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Dynamic Virtual Power Plant Design for Fast Frequency Reserves : Coordinating Hydro and Wind
- 2022
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Ingår i: IEEE Transactions on Control of Network Systems. - : Institute of Electrical and Electronics Engineers (IEEE). - 2325-5870. ; , s. 1-12
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Tidskriftsartikel (refereegranskat)abstract
- To ensure frequency stability in future low-inertia power grids, fast ancillary services such as fast frequency reserves (FFR) have been proposed. In this work, the coordination of conventional (slow) frequency containment reserves (FCR) with FFR is treated as a decentralized model matching problem. The design results in a dynamic virtual power plant (DVPP) whose aggregated output fulfills the system operator’s (SO’s) requirements in all time scales, while accounting for the capacity and bandwidth limitation of participating devices. This is illustrated in a 5-machine representation of the Nordic synchronous grid. In the Nordic grid, stability issues and bandwidth limitations associated with non-minimum phase zeros of hydropower is a well-known problem. By simulating the disconnection of a 1400 MW importing dc link, it is shown that the proposed DVPP design allows for coordinating fast FFR from wind, with slow FCR from hydro, while respecting dynamic limitations of all participating devices. The SO’s requirements are fulfilled in a realistic low-inertia scenario without the need to install battery storage or to waste wind energy by curtailing the wind turbines.
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| 6. |
- Blanchini, Franco, et al.
(författare)
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Aggregates of Monotonic Step Response systems : a structural classification
- 2018
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Ingår i: IEEE Transactions on Control of Network Systems. - 2325-5870. ; 5:2, s. 782-792
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Tidskriftsartikel (refereegranskat)abstract
- Complex dynamical networks can often be analysed as the interconnection of subsystems, to simplify the model and better understand the global behaviour. Some biological networks can be analysed as aggregates of monotone subsystems. Yet, monotonicity is a strong requirement and relies on the knowledge of an explicit state model. Systems with a Monotonic Step Response (MSR), which include input-output monotone systems, are a broader class and have interesting features. The property of having a monotonically increasing step response can be evinced from experimental data. We consider networks that can be decomposed as aggregates of MSR subsystems and we provide a structural (parameter-free) classification of oscillatory and multistationary behaviours. The classification is based on the exclusive or concurrent presence of negative and positive cycles in the system $aggregate graph$, whose nodes are the MSR subsystems. The result is analogous to our earlier classification for aggregates of monotone subsystems. Our classification is applied to models of biomolecular networks and helps build synthetic biomolecular circuits that, by design, are well suited to exhibit the desired dynamics.
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| 7. |
- Charalambous, Themistoklis, et al.
(författare)
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Distributed Finite-Time Average Consensus in Digraphs in the Presence of Time Delays
- 2015
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Ingår i: IEEE Transactions on Control of Network Systems. - : IEEE. - 2325-5870. ; 2:4, s. 370-381
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Tidskriftsartikel (refereegranskat)abstract
- Most algorithms for distributed averaging only guarantee asymptotic convergence. This paper introduces a distributed protocol that allows nodes to find the exact average of the initial values in a finite and minimum number of steps on interconnection topologies described by strongly connected directed graphs (digraphs). More specifically, under the assumption that each component has knowledge of the number of its outgoing links (i.e., the number of components to which it sends information), we show that the average value can be computed based on local observations over a finite time interval. The average can be obtained in a finite number of steps even when the information exchange is subject to delays. The proposed algorithm is the first in the literature that allows for distributed computation of the exact average in digraphs in finite time, with and without delays.
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| 8. |
- Charalambous, Themistoklis, et al.
(författare)
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Distributed Finite-Time Computation of Digraph Parameters : Left-Eigenvector, Out-Degree and Spectrum
- 2016
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Ingår i: IEEE Transactions on Control of Network Systems. - : Institute of Electrical and Electronics Engineers (IEEE). - 2325-5870. ; 3:2, s. 137-148
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Tidskriftsartikel (refereegranskat)abstract
- Many of the algorithms that have been proposed in the field of distributed computation rely on assumptions that require nodes to be aware of some global parameters. In this paper, we propose algorithms to compute some network parameters in a distributed fashion and in a finite number of steps. More specifically, given an arbitrary strongly connected network of interconnected nodes, by adapting a distributed finite-time approach, we develop distributed strategies that enable nodes to compute the following network parameters: the left-eigenvector, the out-degree, and the spectrum of weighted adjacency matrices.
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| 9. |
- Chatterjee, Sarthak, et al.
(författare)
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Discrete-Time Fractional-Order Dynamical Networks Minimum-Energy State Estimation
- 2023
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Ingår i: IEEE Transactions on Control of Network Systems. - : IEEE. - 2325-5870. ; 10:1, s. 226-237
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Tidskriftsartikel (refereegranskat)abstract
- Fractional-order dynamical networks are increasingly being used to model and describe processes demonstrating long-term memory or complex interlaced dependencies among the spatial and temporal components of a wide variety of dynamical networks. Notable examples include networked control systems or neurophysiological networks which are created using electroencephalographic (EEG) or blood-oxygen-level-dependent data. As a result, the estimation of the states of fractional-order dynamical networks poses an important problem. To this effect, this article addresses the problem of minimum-energy state estimation for discrete-time fractional-order dynamical networks, where the state and output equations are affected by an additive noise that is considered to be deterministic, bounded, and unknown. Specifically, we derive the corresponding estimator and show that the resulting estimation error is exponentially input-to-state stable with respect to the disturbances and to a signal that is decreasing with the increase of the accuracy of the adopted approximation model. An illustrative example shows the effectiveness of the proposed method on real-world neurophysiological networks. Our results may significantly contribute to the development of novel neurotechnologies, particularly in the development of state estimation paradigms for neural signals such as EEG, which are often noisy signals known to be affected by artifacts not having any particular stochastic characterization.
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| 10. |
- Chen, Fei, et al.
(författare)
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Leader-follower Formation Control with Prescribed Performance Guarantees
- 2020
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Ingår i: IEEE Transactions on Control of Network Systems. - : Institute of Electrical and Electronics Engineers (IEEE). - 2325-5870.
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Tidskriftsartikel (refereegranskat)abstract
- This paper addresses the problem of achieving relative position-based formation control for leader-follower multi-agent systems in a distributed manner using a prescribed performance strategy. Both the first and second-order cases are treated and a leader-follower framework is introduced in the sense that a group of agents with external inputs are selected as leaders in order to drive the group of followers in a way that the entire system achieves a target formation within certain prescribed performance transient bounds. Under the assumption of tree graphs, a distributed control law is proposed for the first-order case when the decay rate of the performance functions is within a sufficient bound. Then, two classes of tree graphs that can have additional followers are investigated. For the second-order case, we propose a distributed control law based on a backstepping approach for the group ofleaders to steer the entire system achieving the target formation within the prescribed performance bounds. Finally, several simulation examples are given to illustrate the results.
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