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arXiv 2017年

作者： Lupia, Francesco Mendicelli, Angelo Ribichini, Andrea Scarcello, Francesco Schaerf, Marco Dept. of Computer Science Modeling Electronics and Systems Engineering University of Calabria Rende87036 Italy Dept. of Physics Sapienza University Rome00185 Italy Dept. of Computer Control and Management Engineering Antonio Ruberti Sapienza University Rome00185 Italy

In allocation problems, a given set of goods are assigned to agents in such a way that the social welfare is maximised, that is, the largest possible global worth is achieved. When goods are indivisible, it is possible to use money compensation to perform a fair allocation taking into account the actual contribution of all agents to the social welfare. Coalitional games provide a formal mathematical framework to model such problems, in particular the Shapley value is a solution concept widely used for assigning worths to agents in a fair way. Unfortunately, computing this value is a #P-hard problem, so that applying this good theoretical notion is often quite difficult in real-world problems. We describe useful properties that allow us to greatly simplify the instances of allocation problems, without affecting the Shapley value of any player. Moreover, we propose algorithms for computing lower bounds and upper bounds of the Shapley value, which in some cases provide the exact result and that can be combined with approximation algorithms. The proposed techniques have been implemented and tested on a real-world application of allocation problems, namely, the Italian research assessment program, known as VQR. For the large university considered in the experiments, the problem involves thousands of agents and goods (here, researchers and their research products). The algorithms described in the paper are able to compute the Shapley value for most of those agents, and to get a good approximation of the Shapley value for all of them. Copyright © 2017, The Authors. All rights reserved.

关键词： Game theory

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Clustering in block Markov chains

arXiv

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arXiv 2017年

作者： Sanders, Jaron Proutière, Alexandre Yun, Se-Young Kth Royal Institute of Technology School of Electrical Engineering Dept. of Automatic Control Osquldasväg 10 Stockholm10044 Sweden Delft University of Technology Faculty of Electrical Engineering Mathematics and Computer Science Dept. of Quantum and Computer Engineering Mekelweg 4 Delft2628CD Netherlands Korea Advanced Institute of Science and Technology Dept. of Industrial and Systems Engineering 291 Daehak-ro Eoeun-dong Yuseong-gu Korea Republic of

This paper considers cluster detection in Block Markov Chains (BMCs). These Markov chains are characterized by a block structure in their transition matrix. More precisely, the n possible states are divided into a finite number of K groups or clusters, such that states in the same cluster exhibit the same transition rates to other states. One observes a trajectory of the Markov chain, and the objective is to recover, from this observation only, the (initially unknown) clusters. In this paper we devise a clustering procedure that accurately, efficiently, and provably detects the clusters. We first derive a fundamental information-theoretical lower bound on the detection error rate satisfied under any clustering algorithm. This bound identifies the parameters of the BMC, and trajectory lengths, for which it is possible to accurately detect the clusters. We next develop two clustering algorithms that can together accurately recover the cluster structure from the shortest possible trajectories, whenever the parameters allow detection. These algorithms thus reach the fundamental detectability limit, and are optimal in that sense. Copyright © 2017, The Authors. All rights reserved.

关键词： Asymptotic analysis

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Event-based internal model control approach for frequency deviation control in islanded micro grid

Event-based internal model control approach for frequency de...

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International Conference on Emerging Technologies and Factory Automation (ETFA)

作者： R. Vilanova C. Pedret M. Barbu O. Arrieta Deptartment of Telecomunications and Systems Engineering Universitat Autonoma Barcelona Bellaterra Barcelona Spain Dept. Automatic Control and Electrical Eng. Dunarea de Jos University of Galati Galati Romania 2Department of Automatic Control University of Costa Rica San Jose Costa Rica

This work faces the problem of frequency deviation in microgrid systems. The considered microgrid includes renewable energy sources such as wind and solar photovoltaic. As long as these sources provide an irregular power supply or there is a sudden change in the system load, the power system frequency deviates. In order to compensate such deviations, alternative, conventional energy sources should be commanded in order to provide the corresponding power deficit. In this paper a very simple and of common industrial practice control approach such as the Internal Model control based on first order plus time delay models is proposed within an event-based framework. As the commanded energy sources are based on fuel consumption, the control usage has to be maintained at low levels. It is shown that the event-based approach is able to provide accurate frequency deviation control with very low movements for the control signal. Time domain simulations show the effectiveness of the approach as compared with other more sophisticated controllers already proposed in the literature.

关键词： Renewable energy sources Generators Microgrids Solar power generation Load modeling Process control Uncertainty

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Virtual control Labs Experimentation: The Water Tank System

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IFAC-PapersOnLine 2016年第6期49卷 87-92页

作者： Galan, Daniel Heradio, Ruben Torre, Luis de la Dormido, Sebastian Esquembre, Francisco Dept. of Computer Science and Automatic Control Universidad Nacional de Educación a Distancia Juan del Rosal 16 MadridE-28040 Spain Dept. of Software Engineering and Computer Systems Universidad Nacional de Educación a Distancia Juan del Rosal 16 MadridE-28040 Spain Dept. of Mathematics Universidad de Murcia Campus de Espinardo MurciaE-30071 Spain

This paper describes a new way to perform automated experiments using virtual laboratories. Experiments are developed and executed using a new software tool: the Experiment Editor. This tool uses virtual laboratories applications designed with educational purposes. The main features/advantages of the Experiment Editor are: 1) the possibility of modifying the initial functionality of the laboratories (i.e. adding new controllers to the plant), 2) analyzing the obtained results during the experiment and performing complex or repetitive tasks in a simple way, 3) and any others explained in the paper. To illustrate the utility of the Experiment Editor a very well-known system is used: the water tank system. © 2016

关键词： Distance education computer aided software engineering computer software Experiments Laboratories Water tanks Easy java(script) Simulations Experimentation Language Repetitive task Simulations Tank system Tool use Virtual control Virtual laboratories

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Multiagent coverage problems: The trade-off between anarchy and stability

arXiv

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arXiv 2017年

作者： Ramaswamy, Vinod Paccagnan, Dario Marden, Jason R. Dept. of Electrical Computer and Energy Engineering University of Colorado BoulderCO80309 United States Automatic Control Laboratory ETH Zürich Zurich Switzerland Electrical and Computer Engineering Department UC Santa Barbara Santa BarbaraCA93106 United States

Networked systems are ubiquitous in today's world with examples spanning from ecology to the social and engineering sciences. Much of the research in networked systems is analytical, where the focus is on characterizing (and potentially inuencing) the emergent collective behavior, e.g., predicting the distribution of animals and humans in a given ecological system. A more recent trend of research focuses on the design of networked systems capable of achieving diverse and highly coordinated collective behavior in the absence of centralized control, e.g., designing a team of unmanned aerial vehicles to monitor the perimeter of a wild fire. Unfortunately, our understanding of how microscopic behavior impacts the macroscopic phenomena in network systems is inadequate for meeting the demands of this emerging design task. This paper focuses on an instance of this design task for a well-studied class of coverage problems where the goal is to allocate a collection of agents to a subset of resources in order to maximize the cumulative value of the covered resources. Our first result demonstrates that any agent-based algorithm relying solely on local information induces a fundamental trade-off between the best and worst case performance guarantees, as measured by the price of anarchy and price of stability. This result highlights how the information available to the agents translates to constraints on the achievable efficiency guarantees in networked control systems. Our second results demonstrates how to use an additional piece of system-level information to breach these limitations, thereby improving the system's performance. Copyright © 2017, The Authors. All rights reserved.

关键词： Networked control systems

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Optimal distributed control for platooning via sparse coprime factorizations

Optimal distributed control for platooning via sparse coprim...

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2016 American control Conference, ACC 2016

作者： SabǍu, Şerban OarǍ, Cristian Warnick, Sean Jadbabaie, Ali Electrical and Computer Engineering Dept. Stevens Institute of Technology HobokenNJ United States Automatic Control Dept. University Politehnica Bucharest Romania Information and Decision Algorithms Laboratories Faculty of the Computer Science Department Brigham Young University United States Electrical and Systems Engineering Dept. University of Pennsylvania United States

ISBN: (纸本)9781467386821

We introduce a novel distributed control architecture for disturbances attenuation in heterogeneous platoons of linear and time-invariant autonomous agents that inherits the performance achievable by the leader-follower control policies. We provide a Youla-like parameterization for the class of all distributed controllers such that the sparsity constraints are imposed on the controllers' left coprime factors, outlining a new concept of structural constraints in distributed control. The proposed scheme lends itself to optimal controller design via norm based costs, it guarantees string stability and completely eliminates the accordion effect from the behavior of the platoon. The distributed controller is proven to attain global optimality for heterogeneous platoons and H2 costs and can easily reconfigure such as to remain optimal during formation merging/exiting maneuvers. The scheme is amenable to a GPS time base synchronization mechanism, allowing for the exact compensation of the time delays induced by the wireless communications. © 2016 American automatic control Council (AACC).

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An analysis on the reliability of a series of texture and shape descriptors for melanoma diagnosis

UPB Scientific Bulletin, Series C: Electrical Engineering an...

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UPB Scientific Bulletin, Series C: Electrical engineering and computer Science 2016年第2 2期78 78卷 23-34页

作者： Udrea, Andreea Popescu, Dumitru Miron, Cristian Dept. of Automatic Control and Systems Engineering University Politehnica of Bucharest Romania

Early detection of melanoma can substantially reduce the mortality rate associated to this aggressive type of skin cancer. In this paper, a series of second order statistics texture descriptors are investigated for relevance in (normalised) RGB, HSV, YCrCb CIEXYZ and CIELab color spaces, along with a series of shape features. The best results are obtained for the following shape descriptors: contour asymmetry index, circularity index and mass-radius fractal dimension and for the following texture descriptors: uniformity for the RGB channels. These can be used along with other skin lesions descriptors for a high accuracy automated classification algorithm for melanoma early detection.

关键词： Fractal dimension

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Computing the Shapley value in allocation problems: Approximations and bounds, with an application to the Italian VQR research assessment program 23

Computing the Shapley value in allocation problems: Approxim...

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23rd RCRA International Workshop on Experimental Evaluation of Algorithms for Solving Problems with Combinatorial Explosion, RCRA 2016

In allocation problems, a given set of goods are assigned to agents in such a way that the social welfare is maximized, that is, the largest possible global worth is achieved. When goods are indivisible, it is possible to use money compensation to perform a fair allocation taking into account the actual contribution of all agents to the social welfare. Coalitional games provide a formal mathematical framework to model such problems, in particular the Shapley value is a solution concept widely used for assigning worths to agents in a fair way. Unfortunately, computing this value is a #P-hard problem, so that applying this good theoretical notion is often quite difficult in real-world problems. In this paper, we first review the application of the Shapley value to an allocation problem that models the evaluation of the Italian research structures with a procedure known as VQR. For large universities, the problem involves thousands of agents and goods (here, researchers and their research products). We then describe some useful properties that allow us to greatly simplify many such large instances. Moreover, we propose new algorithms for computing lower bounds and upper bounds of the Shapley value, which in some cases provide the exact result and that can be combined with approximation algorithms. The proposed techniques have been tested on large real-world instances of the VQR research evaluation problem.

关键词： Approximation algorithms

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Magnetic shocks and substructures excited by torsional Alfvén wave interactions in merging expanding flux tubes

arXiv

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arXiv 2018年

作者： Snow, B. Fedun, V. Gent, F.A. Verth, G. Erdélyi, R. School of Mathematics and Statistics University of Sheéld S3 7RH United Kingdom Department of Automated Control and Systems Engineering University of Sheéld S1 3JD United Kingdom Department of Computer Science ReSoLVE Centre of Excellence Aalto University PO Box 15400 HelsinkiFI-00076 Finland Dept. of Astronomy Eötvös L. University Pazmany Peter sétány 1/A BudapestH-1117 Hungary

Vortex motions are frequently observed on the solar photosphere. These motions may play a key role in the transport of energy and momentum from the lower atmosphere into the upper solar atmosphere, contributing to coronal heating. The lower solar atmosphere also consists of complex networks of ux tubes that expand and merge throughout the chromosphere and upper atmosphere. We perform numerical simulations to investigate the behaviour of vortex driven waves propagating in a pair of such ux tubes in a non-force-free equilibrium with a realistically modelled solar atmosphere. The two ux tubes are independently perturbed at their footpoints by counter-rotating vortex motions. When the ux tubes merge, the vortex motions interact both linearly and nonlinearly. The linear interactions generate many small-scale transient magnetic substructures due to the magnetic stress imposed by the vortex motions. Thus, an initially monolithic tube is separated into a complex multi-threaded tube due to the photospheric vortex motions. The wave interactions also drive a superposition that increases in amplitude until it exceeds the local Mach number and produces shocks that propagate upwards with speeds of approximately 50 km s1. The shocks act as conduits transporting momentum and energy upwards, and heating the local plasma by more than an order of magnitude, with peak temperature approximately 60;000 K. Therefore, we present a new mechanism for the generation of magnetic waveguides from the lower solar atmosphere to the solar corona. This wave guide appears as the result of interacting perturbations in neighbouring ux tubes. Thus, the interactions of photospheric vortex motions is a potentially significant mechanism for energy transfer from the lower to upper solar atmosphere. Copyright © 2018, The Authors. All rights reserved.

关键词： Magnetohydrodynamics

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control of greenhouse with parabolic trough collectors

UPB Scientific Bulletin, Series C: Electrical Engineering an...

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UPB Scientific Bulletin, Series C: Electrical engineering and computer Science 2016年第3期78卷 75-84页

作者： Grigoriu, Ramona-Oana Voda, Alina Arghira, Nicoleta Calofir, Vasile Iliescu, Sergiu Stelian Faculty of Automatic Control and Computer Science University Politehnica of Bucharest Romania Dept. of Control Systems GIPSA-Lab University Joseph Fourier Grenoble 1 France

Resource management in nowadays agriculture imposes the use of new technological solutions for automation and energy efficiency and this paper concentrates on the control of internal temperature of a greenhouse using parabolic trough collectors (GHPTC) for internal heating. The actuator for the GHPTC control system is the conducting fluid pump that enables the liquid flow into the collector pipes. Both the nonlinear and linear models are presented in the paper in order to tune a classical controller. A comparison of controller performances (stationary and transient) was conducted by simulation, using Matlab/Simulink software. Also, the gradient descent method was applied for an optimal tuning of the temperature controller, imposing minimum overshoot.

关键词： Greenhouses

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