| 1. |
- Andersson, Alina, et al.
(författare)
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Sufficient Conditions for Dynamic Stabilization of 3-State Moore-Greitzer Compressor Model
- 2015
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Ingår i: 2015 IEEE 54th Annual Conference on Decision and Control (CDC). - 9781479978861 - 9781479978847 ; , s. 4394-4399
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Konferensbidrag (refereegranskat)abstract
- We consider the classical 3-state Moore-Greitzer model, which is commonly used for approximating dynamics of deviations of flow and pressure variables in an axial compressor from their nominal steady-state values. The linearization of the nonlinear system is not controllable and, therefore, even local asymptotic stability cannot be achieved using methods of linear control theory. We propose a family of parametrized partialstate feedback control laws and derive sufficient conditions to guarantee global asymptotic stability of the closed-loop system. The stability analysis uses the integral quadratic constraints technique for the case of non-strict frequency condition and novel arguments for characterization of omega-limit sets.
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| 2. |
- Andreasson, Martin, 1987-, et al.
(författare)
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Distributed Secondary Frequency Control through MTDC Transmission Systems
- 2015
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Ingår i: Decision and Control (CDC), 2015 IEEE 54th Annual Conference on. - : IEEE conference proceedings. - 9781479978847 ; , s. 2627-2634
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Konferensbidrag (refereegranskat)abstract
- In this paper, we present distributed controllers for sharing primary and secondary frequency control reserves for asynchronous AC transmission systems, which are connected through a multi-terminal HVDC grid. By using passivity arguments, the equilibria of the closed-loop system are shown to be globally asymptotically stable. We quantify the static errors of the voltages and frequencies, and give upper bounds for these errors. It is also shown that the controllers have the property of power sharing, i.e., primary and secondary frequency control reserves are shared fairly amongst the AC systems. The proposed controllers are applied to a high-order dynamic model of of a power system consisting of asynchronous AC grids connected through a 6-terminal HVDC grid.
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| 3. |
- Cubo, Rubén, et al.
(författare)
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Electric field modeling and spatial control in Deep Brain Stimulation
- 2015
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Ingår i: Proc. 54th Conference on Decision and Control. - Piscataway, NJ : IEEE. - 9781479978847 - 9781479978861 ; , s. 3846-3851
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Konferensbidrag (refereegranskat)abstract
- Deep Brain Stimulation (DBS) is an established treatment, in e.g. Parkinson's Disease, whose underlying biological mechanisms are unknown. In DBS, electrical stimulation is delivered through electrodes surgically implanted into certain regions of the brain of the patient. Mathematical models aiming at a better understanding of DBS and optimization of its therapeutical effect through the simulation of the electrical field propagating in the brain tissue have been developed in the past decade. The contribution of the present study is twofold: First, an analytical approximation of the electric field produced by an emitting contact is suggested and compared to the numerical solution given by a Finite Element Method (FEM) solver. Second, the optimal stimulation settings are evaluated by fitting the field distribution to a target one to control the spread of the stimulation. Optimization results are compared to those of a geometric approach, maximizing the intersection between the target and the activated volume in the brain tissue and reducing the stimulated area beyond said target. Both methods exhibit similar performance with respect to the optimal stimuli, with the electric field control approach being faster and more versatile.
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| 4. |
- Feyzmahdavian, Hamid Reza, et al.
(författare)
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An Asynchronous Mini-Batch Algorithm for Regularized Stochastic Optimization
- 2015
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Ingår i: 2015 54th IEEE Conference on Decision and Control (CDC). - : IEEE. - 9781479978847 ; , s. 1384-1389
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Konferensbidrag (refereegranskat)abstract
- Mini-batch optimization has proven to be a powerful paradigm for large-scale learning. However, the state of the art mini-batch algorithms assume synchronous operation or cyclic update orders. When worker nodes are heterogeneous (due to different computational capabilities, or different communication delays), synchronous and cyclic operations are inefficient since they will leave workers idle waiting for the slower nodes to complete their work. We propose an asynchronous mini-batch algorithm for regularized stochastic optimization problems that eliminates idle waiting and allows workers to run at their maximal update rates. We show that the time necessary to compute an ϵ-optimal solution is asymptotically O(1/ϵ2), and the algorithm enjoys near-linear speedup if the number of workers is O(1/√ϵ). Theoretical results are confirmed in real implementations on a distributed computing infrastructure.
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| 5. |
- Galrinho, Miguel, et al.
(författare)
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On Estimating Initial Conditions in Unstructured Models
- 2015
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Ingår i: 2015 54th IEEE Conference on Decision and Control (CDC). - : IEEE conference proceedings. - 9781479978847 ; , s. 2725-2730
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Konferensbidrag (refereegranskat)abstract
- Estimation of structured models is an importantproblem in system identification. Some methods, as an intermediatestep to obtain the model of interest, estimate theimpulse response parameters of the system. This approachdates back to the beginning of subspace identification and isstill used in recently proposed methods. A limitation of thisprocedure is that, when obtaining these parameters from ahigh-order unstructured model, the initial conditions of thesystem are typically unknown, which imposes a truncation ofthe measured output data for the estimation. For finite samplesizes, discarding part of the data limits the performance ofthe method. To deal with this issue, we propose an approachthat uses all the available data, and estimates also the initialconditions of the system. Then, as examples, we show how thisapproach can be applied to two methods in a beneficial manner.Finally, we use a simulation study to exemplify the potential ofthe approach.
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| 6. |
- Kadhim, Ali, et al.
(författare)
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Relative Gain Array Variation for Norm Bounded Uncertain Systems
- 2015
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Ingår i: IEEE 54th Annual Conference on Decision and Control (CDC). - Piscataway, NJ : IEEE Communications Society. - 9781479978847 ; , s. 5959-5965
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Konferensbidrag (refereegranskat)abstract
- This article proposes computationally tractable, easyto expand and tight relative gain variation bound for uncertain systems. The proposed bound is a further development of previous work, which is summarized anddiscussed. Using several examples, the new method is compared with previous results and the advantages are highlighted. The prediction of sign changes in relative gain array elements due to uncertainties is important for pairing decisions. Based on the proposed bound,a method for the prediction of the uncertainty levels which render sign changes is suggested. The prediction method is currently limited to certain classes of systems.In this prediction method neither prior knowledge of the uncertainty nor numerous calculations are needed.
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| 7. |
- Lucchese, Riccardo, et al.
(författare)
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Network cardinality estimation using max consensus : the case of Bernoulli trials
- 2015
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Ingår i: IEEE 54th Annual Conference on Decision and Control (CDC). - Piscataway, NJ : IEEE Communications Society. - 9781479978847 ; , s. 895-901
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Konferensbidrag (refereegranskat)abstract
- Interested in scalable topology reconstruction strategies with fast convergence times, we consider network cardinality estimation schemes that use, as their fundamental aggregation mechanism, the computation of bit-wise maxima over strings. We thus discuss how to choose optimally the parameters of the information generation process under frequentist assumptions on the estimand, derive the resulting Maximum Likelihood (ML) estimator, and characterize its statistical performance as a function of the communications and memory requirements. We then numerically compare the bitwise-max based estimator against lexicographic-max based estimators, and derive insights on their relative performances in function of the true cardinality.
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| 8. |
- Nilsson, Gustav, et al.
(författare)
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Entropy-like Lyapunov Functions for the Stability Analysis of Adaptive Traffic Signal Controls
- 2016
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Ingår i: Proceedings of the IEEE Conference on Decision and Control. - 9781479978847 ; , s. 2193-2198
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Konferensbidrag (refereegranskat)abstract
- Stability of some decentralized traffic signal control policies for urban traffic networks is studied. It is proven that, whenever the arrival rates belong to a certain region -which is the largest where stability is possible- the resulting traffic network dynamics admit a globally asymptotically stable equilibrium. The results rely on the use of some entropy-like Lyapunov functions previously considered in the context of stochastic queuing networks.
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| 9. |
- Papadopoulos, Alessandro Vittorio, et al.
(författare)
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Virtual Machine Migration in Cloud Infrastructures: Problem Formalization and Policies Proposal
- 2016
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Ingår i: 2015 54th IEEE Conference on Decision and Control (CDC). - 9781479978847 ; , s. 6698-6705
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Konferensbidrag (refereegranskat)abstract
- Cloud computing has dramatically simplified the deployment of new software and, indeed, the number of applications that are hosted by cloud providers every day is increasing. The data center owner should provide computing capacity to a set of customers, each of them powering up and down virtual machines dynamically, to handle variations in the incoming requests. Cloud providers, however, should also optimize for quantities like energy consumption and managements costs, therefore trying to host all the customers virtual machines with the fewest amount of physical hardware machines possible. This leads to virtual machine co-location and potential performance inefficiency. To limit the inefficiency, virtual machines are migrated from one physical machine to another when overload conditions are detected. This paper analyzes the problem of virtual machine migration and presents some heuristic solutions to decide when to migrate a virtual machine from a physical machine to a different one. Experimental results show the differences between the proposed heuristics, providing a basis for a fair comparison among the techniques.
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| 10. |
- Precious, Ugo Abara, et al.
(författare)
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Existence, uniqueness and stability properties of positive equilibria for a class of nonlinear cooperative systems
- 2015
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Ingår i: Proceedings of 54th IEEE Conference on Decision and Control (CDC). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781479978861 - 9781479978847 - 9781479978854 ; , s. 4406-4411
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Konferensbidrag (refereegranskat)abstract
- We provide conditions that guarantee existence, uniqueness and stability of strictly positive equilibria for nonlinear cooperative systems associated to vector fields that are concave or subhomogeneous. This class of positive systems describes well interconnected dynamics that are of key interest for communication, biological, economical and neural network applications. These conditions can be formulated directly in terms of the spectral radius of the Jacobian of the system, and do not require to use constant inputs to move the equilibrium point from the origin to the interior of the positive orthant.
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