4,121 research outputs found
Networked Control Systems: The Communication Basics and Control Methodologies
As an emerging research field, networked control systems have shown the increasing importance and attracted more and more attention in the recent years. The integration of control and communication in networked control systems has made the design and analysis of such systems a great theoretical challenge for conventional control theory. Such an integration also makes the implementation of networked control systems a necessary intermediate step towards the final convergence of control, communication, and computation. We here introduce the basics of networked control systems and then describe the state-of-the-art research in this field. We hope such a brief tutorial can be useful to inspire further development of networked control systems in both theory and potential applications
Towards a Global Controller Design for Guaranteed Synchronization of Switched Chaotic Systems
This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.In this paper, synchronization of identical switched chaotic systems is explored based on Lyapunov theory of guaranteed stability. Concepts from robust control principles and switched linear systems are merged together to derive a sufficient condition for synchronization of identical master-slave switched nonlinear chaotic systems and are expressed in the form of bilinear matrix inequalities (BMIs). The nonlinear controller design problem is then recast in the form of linear matrix inequalities (LMIs) to facilitate numerical computation by standard LMI solvers and is illustrated by appropriate examples
Dirac fermions in strong electric field and quantum transport in graphene
Our previous results on the nonperturbative calculations of the mean current
and of the energy-momentum tensor in QED with the T-constant electric field are
generalized to arbitrary dimensions. The renormalized mean values are found;
the vacuum polarization and particle creation contributions to these mean
values are isolated in the large T-limit, the vacuum polarization contributions
being related to the one-loop effective Euler-Heisenberg Lagrangian.
Peculiarities in odd dimensions are considered in detail. We adapt general
results obtained in 2+1 dimensions to the conditions which are realized in the
Dirac model for graphene. We study the quantum electronic and energy transport
in the graphene at low carrier density and low temperatures when quantum
interference effects are important. Our description of the quantum transport in
the graphene is based on the so-called generalized Furry picture in QED where
the strong external field is taken into account nonperturbatively; this
approach is not restricted to a semiclassical approximation for carriers and
does not use any statistical assumtions inherent in the Boltzmann transport
theory. In addition, we consider the evolution of the mean electromagnetic
field in the graphene, taking into account the backreaction of the matter field
to the applied external field. We find solutions of the corresponding
Dirac-Maxwell set of equations and with their help we calculate the effective
mean electromagnetic field and effective mean values of the current and the
energy-momentum tensor. The nonlinear and linear I-V characteristics
experimentally observed in both low and high mobility graphene samples is quite
well explained in the framework of the proposed approach, their peculiarities
being essentially due to the carrier creation from the vacuum by the applied
electric field.Comment: 24 pages, 1 figure; version accepted for publication in Physical
Review D., some comments adde
Onset and stabilization of delay-induced instabilities in piezoelectric digital vibration absorbers
The stability of a piezoelectric structure controlled by a digital vibration
absorber emulating a shunt circuit is investigated in this work. The formalism
of feedback control theory is used to demonstrate that systems with a low
electromechanical coupling are prone to delay-induced instabilities entailed by
the sampling procedure of the digital unit. An explicit relation is derived
between the effective electromechanical coupling factor and the maximum
sampling period guaranteeing a stable controlled system. Since this sampling
period may be impractically small, a simple modification procedure of the
emulated admittance of the shunt circuit is proposed in order to counteract the
effect of delays by anticipation. The theoretical developments are
experimentally validated on a clamped-free piezoelectric beam
CONSENSUS BASED DISTRIBUTED CONTROL IN MICRO-GRID CLUSTERS
With the increasing trend of utilizing renewable energy generators such as photovoltaic (PV) cells and wind turbines, power systems are transforming from a centralized power grid structure to a cluster of smart micro-grids with more autonomous power sharing capabilities. Even though the decentralized control of power systems is a reliable and cost effective solution, due to the inherent heterogeneous nature of micro-grids, optimal and efficient power sharing among distributed generators (DG’s) is a major issue which calls for advanced control techniques for voltage stabilization of the entire micro-grid cluster. The proposed consensus based algorithm in this thesis is a solution to overcome these control challenges, which only requires each DG to exchange information with its directly connected neighboring DG’s, in order to maintain the power balance and voltage stability of the entire micro-grid cluster. The proposed method in this thesis is simulated in PSCAD and its effectiveness is demonstrated using several realistic and practical cases including micro-grid topology changes, communication delays, and load changes
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