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Control & Automation (MED), 2011 19th Mediterranean Conference on

Date 20-23 June 2011

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Displaying Results 1 - 25 of 265
  • [Front cover]

    Page(s): c1
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  • [Copyright notice]

    Page(s): 1
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  • MED11 conference Organizing Committee

    Page(s): 1 - 2
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  • A message from the president of the Mediterranean Control Association (MCA)

    Page(s): 1 - 2
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  • MED11- Plenary Session 1

    Page(s): 1 - 4
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  • Content list of 19th mediterranean conference on control and automation

    Page(s): 1 - 31
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  • MED 2011 author index

    Page(s): 1 - 13
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  • MED 2011 keyword index

    Page(s): 1 - 2
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  • Passivity indices for symmetrically interconnected distributed systems

    Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (165 KB) |  | HTML iconHTML  

    In this paper, the passivity indices for both linear and nonlinear multi-agent systems with feedforward and feedback interconnections are derived. For linear systems, the passivity indices are explicitly characterized, while the passivity indices in the nonlinear case are characterized by a set of matrix inequalities. We also focus on symmetric interconnections and specialize the passivity indices results to this case. An illustrative example is also given. View full abstract»

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  • Distributed backstepping control for synchronization of networked class of underactuated systems: A passivity approach

    Page(s): 7 - 12
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (184 KB) |  | HTML iconHTML  

    This paper considers the cooperative control problem of networked class of underactuated systems. We propose a new set up for synchronization of this type of systems based on the use of passivity as a design tool to solve the problem in hand. First the underactuated system is transformed to a class of nonlinear system with chain structure using a suitable non-linear static feedback. The cooperative control is designed using a combination of the standard backstepping procedure and the passivity theory by which a synchronizing outputs are constructed recursively then shared within the group. The proposed design technique is based on strongly connected digraph communication structures. Numerical simulations are carried out to illustrate the effectiveness of the proposed approach. View full abstract»

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  • Modeling real networks with deterministic preferential attachment

    Page(s): 13 - 18
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    Most of real networks show a structure that can be represented quite well by means of growth and probabilistic preferential attachment, leading to optimal features, such as high clustering or scale-freeness. Real networks, however, are not the result of a global optimization strategy; indeed it is more realistic to let new nodes selfishly chose to connect to the existing nodes that maximize their utility, regardless of the global optimality of the resulting network. On the other hand real networks exist and deploy in metric spaces; spatial network models are characterized by some properties because the generated nodes are discarded if they do not comply with some criteria (e.g., too far from existing nodes), while in real situations the arise of a new node in a given position can not be neglected. In this paper a model for the representation of such net works is provided, considering spatial and degree based utility functions, as well as their combination. While the nodes are generated randomly, the preferential attachment strategy is deterministic, and is univocally determined, given the sequence of nodes and the utility to be maximized. The proposed model, although created according to the immediate benefit of nodes, shows some of the properties that can be obtained with global optimization strategies based on probability. A possible application of the proposed model is a linking strategy for a set of distributed dynamic agents (e.g., mobile robots embedded in a space) based on the single agents' perspective, which ensures the connectedness of the resulting network (while other spatial network models give no guarantee), as well as some desirable properties such as reduced total edge length that may minimize the communication time and small diameter, that influences convergence. View full abstract»

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  • Novel ODE-type nonlinear smith predictor for networked control systems with time-varying delay

    Page(s): 19 - 24
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (180 KB) |  | HTML iconHTML  

    This paper discusses the stability analysis of networked control systems (NCSs) with time-varying delays. In an NCS, the presence of time delays in the transmission may severely affect the performance of the closed-loop system and prevent the successful application of established nonlinear control methodologies. First, we present the backstepping interpretation of Smith predictors for linear time-variant systems in the state space. Second, we present a design and stability analysis for the control of a nonlinear Smith predictor and propose a new control scheme. The Smith predictor provides a set of future control predictions to make the closed-loop system achieve the desired control performance. View full abstract»

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  • Robust/reliable stabilization of multi-channel systems via dilated LMIs and dissipativity-based certifications

    Page(s): 25 - 30
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (306 KB) |  | HTML iconHTML  

    In this paper, we consider the problem of reliable stabilization for a multi-channel system, where our main objective is to maintain the stability of the perturbed closed-loop system and when there is a single controller failure in any of the control channels. We specifically present a computationally tractable and less-conservative result in terms of a set of dilated LMIs for the reliable state feedback stabilization of the nominal system, while a dissipativity-based certification is used to extend the stability condition under model perturbation in the system. Finally, a numerical example is used to demonstrate the applicability of the proposed technique. View full abstract»

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  • Building simulation/emulation environments for home automation systems

    Page(s): 31 - 38
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    The growing interest for developing intelligent and user-friendly systems that take care of various tasks in home management has forested, in the last years, the study of architectures and behavioral strategies for home automation systems. From a theoretical point of view, home automation systems present great complexity, due to their hybrid, distributed and heterogeneous structure, which makes the problem of allocating limited resources like electricity, gas and water very difficult. In this paper, we propose a general methodology for modeling, in a Multi Agent System fashion, home automation systems and for constructing an efficient simulation/emulation environment. Our approach employ an UML point of view for constructing models of individual appliances and domotic devices, called agents, whose structure replicates the coupling between real appliances and real actuated/monitored plugs. Generic models consist of a switched dynamics governed by a Petri net, which provides the interface between agents and with the environment. Glowing together, in a suitable way, the Petri net components of agents sharing a common resource, it is possible to define the structure of an overall system that describes concurrent use of that resource. In order to cope with constrains and limitation of resources, the overall system can be endowed with a suitable controller, giving rise to what we call an Home Automation System. Thank to their structures, abstract models and real appliances can be combined into emulation environment where the performances of controllers and related control strategies can be easily investigated. Our approach provide therefore a general methodology for supporting design and validation of control strategies for home automation systems. View full abstract»

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  • Optimization and control of a distributed Battery Energy Storage System for wind power smoothing

    Page(s): 39 - 43
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (171 KB) |  | HTML iconHTML  

    This paper presents a methodology to minimize the capacity of a Battery Energy Storage System (BESS) in a distributed configuration of wind power sources. A new semi-distributed BESS scheme is proposed to improve the suppression of the fluctuations in the wind farm power output. The proposed control system is tested for two dissimilar power profiles of the turbines where the turbines are located far from each other geographically. The scheme is analyzed under a variety of hard system constraints. It was observed that the performance of the proposed semi-distributed BESS scheme is better than that of conventional approaches. View full abstract»

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  • Modeling and control of the energy consumption of a prototype urban vehicle

    Page(s): 44 - 48
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1050 KB) |  | HTML iconHTML  

    This paper presents a model of an urban vehicle that was specifically designed for low energy consumption. It is the first but crucial step towards the installation of an automated energy management system on the vehicle. The powertrain of the vehicle consists of a fuel (H2) cell system, an ultra-capacitor bank, a DC/DC converter, a motor controller and an electric motor. The overall system is modeled and simulated in MATLAB. Further, an energy management strategy is described and tested. It consists of two fuzzy logic controllers, which are responsible for the distribution of power needs between the fuel cell and the capacitors, aiming in maximizing the performance and improving the fuel consumption. Several test cases are presented and compared to the on-off control approach. View full abstract»

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  • A model-assisted adaptive controller fine-tuning methodology for efficient energy use in buildings

    Page(s): 49 - 54
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (649 KB) |  | HTML iconHTML  

    Building Energy Management Systems are finding widespread use for the holistic control of all energy-influencing elements of buildings and are responsible for ensuring an effective and parsimonious energy use. In most cases, fixed logic controllers are deployed in the building to implement predetermined strategies. Good performance can not be guar anteed due to inherent uncertainties that can not be a priori ascertained, such as weather variations, occupant actions, and changes in the building state and characteristics. In this paper, a model-assisted tuning methodology is presented to adaptively and automatically fine-tune relevant controller parameters. In our approach, at the end of each day of the building operation, given "reasonable" predictions for the following day, and using an accurate thermal-simulation model to evaluate performance, a new set of controller parameters is generated to be used the following day. This way, good performance can be achieved using controllers with simple mathematical structure. View full abstract»

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  • Current control of a PEMFC system connected to an electrical load through a DC/DC converter

    Page(s): 55 - 60
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    Polymer electrolyte membrane fuel cells are highly efficient energy converters with water and heat as the only reaction products when hydrogen is used as fuel. As compared to auxiliary power units that are currently used for power generation on aircrafts, the fuel cell technology has the potential of significantly reducing emissions and noise. Applications such as power generation, water production and the use of the byproduct oxygen depleted exhaust air are part of the multifunctional use of the fuel cell technology. Cathode exhaust air having the correct oxygen concentration can be utilized such as for kerosene tank inerting. For a given air mass flow provided by the compressor as the fuel cell air supply system a certain oxygen concentration establishes depending on the stack current consumed. In this study a self-powered fuel cell system is connected to an electrical load through a dc/dc converter. As the dc/dc converter parameters are not exactly known a feedforward control of the load current would unavoidably lead to drawing too much or too little fuel cell current. A controller architecture that accounts for the correct consumption of fuel cell current is presented here. View full abstract»

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  • A Krasovskii-LaSalle theorem for behavior: Output persistent excitation and detectability

    Page(s): 61 - 66
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (266 KB) |  | HTML iconHTML  

    This paper studies stability properties for those systems modeled as behaviors that roughly speaking, describe systems using the view-point of signals. Popular examples include of continuous-time systems, discrete-time systems, switched systems, hybrid systems and time-delay systems. By introducing the output persistently exciting (for short, OPE) condition, a general result regarding the OPE conditions of two behaviors is proposed. An output zeroing system and a detectability condition are then used to help the verification of the OPE condition. From this, a type of Krasovskii-LaSalle theorem can be proposed for behavior. The achieved result could be applied to general dynamic systems. Particularly, it is applied to time-delay time-varying systems as a demonstration. A simple example is also provided to show the effectiveness of the proposed result. View full abstract»

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  • Observer-based control strategies for compensation of dynamic friction

    Page(s): 67 - 72
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (579 KB) |  | HTML iconHTML  

    This paper describes and compares different observer-based control strategies for compensating the dynamic friction in controlled motion systems. The once identified system with friction requires usually an observer due to unknown disturbances and time variant friction behavior. The recently developed two-state dynamic friction model with elasto-plasticity is applied within three different types of observer, all involved in the control loop. Each of the observer-based compensation schemes as well as the friction model in feed-forwarding augments a standard linear feedback velocity control which serves for evaluation as the reference one. The performance of the realized control approaches is evaluated on an ordinary electro-mechanical actuator system with multiple coupled sources of friction without its direct measurement. View full abstract»

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  • A statistical tool for analysing nonlinear properties of dynamical systems

    Page(s): 73 - 78
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    A novel statistical indicator is introduced to evaluate the nonlinear behaviour of dynamical systems, as a support to other classic methods (e.g., Lyapunov exponents, entropy of curve methods). According to the theoretical properties of the proposed method, it is possible to infer the actual dimension of the phase space where the system dynamics evolve; it is possible to differentiate linear from nonlinear systems also in the presence of measurement noise; different dynamical systems that appear similar according to other indicators are further correctly distinguished. Theoretical expectations are confirmed by several examples of classic benchmark dynamical systems. View full abstract»

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  • Nonlinear feedback control of a HIV-1 infection model

    Page(s): 79 - 84
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    Nonlinear feedback is investigated to define control strategies for a nonlinear model of HIV-1 model. The proposed control architecture comprises two feedback loops, the inner loop is used to obtain a linear dynamic model using the number of virion particles and the total of CD4+T cells, and the outer loop is used as a supervisor that defines and adjusts the command for the inner loop to attain the target reference. The nonlinear controller is developed in the continuous time frame work, where the total of CD4+T cells (healthy and infected) and the number of virion particles are measured continuously. This paper considers just the administration of RTI drugs for the sake of simplicity in explaining the methodology proposed, that is, the direct manipulation of the efficiency of the drugs. A discrete time version is also presented. The nonlinear control law enables a decoupling between the dynamics of healthy, infected cells and the virion particles, and it also enables the identification of useful parameters that help the supervisor to handle parameter uncertainty. Stability analysis shows that proposed control law stabilizes the nonlinear HIV-1 model. View full abstract»

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  • State and parameter estimation using Chebyshev integral operator

    Page(s): 85 - 89
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (338 KB) |  | HTML iconHTML  

    To formulate estimation problem for a observed nonlinear system, differential equations are required as a system model. We recast those equations as integral equations and apply integral operator, which is approximated by Chebyshev interpolating polynomial. Resulting equations of the nonlinear estimation problem are integral equations discretized on the grid of Chebyshev points. A sequence of linear least squares problems are solved iteratively. Grid resolution can be determined automatically to maximize computation accuracy. Numerical efficiency is achieved by applying iterative method that requires only matrix-vector multiplications, and via implementation of Discrete Cosine Transform when solving indefinite integrals. The estimation algorithm works with matrices having bounded low condition number compared to large and unbounded condition number for the formulation with differential operator. This achievement has important practical value when applying the algorithm with high-order models when the differential operator formulation is typically ill-conditioned. Application to a Duffing system having chaotic response, has been used to illustrate advantages of the proposed estimation algorithm based on Chebyshev integral operator. View full abstract»

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  • Design of observers with arbitrary exponential convergence rate for discrete-time descriptor systems

    Page(s): 90 - 95
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB) |  | HTML iconHTML  

    This paper presents a new state observer for linear discrete-time descriptor systems. By employing the Lyapunov theory, it is proven that if the five coefficients of the proposed observer satisfy the three given matrix equations then the observer has an exponential convergence that its rate is chosen by designer. The mentioned three matrix equations are analyzed, and the procedure of determining observer coefficients is described in details. A numerical example is given to show the design method and illustrate the effectiveness of the proposed observer. View full abstract»

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  • An iterative approach for the description of null controllable regions of discrete-time linear systems with saturating inputs

    Page(s): 96 - 101
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (336 KB) |  | HTML iconHTML  

    In this paper an iterative characterization of the null controllable region for discrete-time linear systems subject to input saturation with unstable eigenvalues is proposed. First an outer estimate of the null controllable region by means of invariant hyperparallelograms is obtained and then an iterated convexification technique is developed. Theoretical developments are supported by some illustrative examples. View full abstract»

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