47,351 research outputs found
Optimal Control for LQG Systems on Graphs---Part I: Structural Results
In this two-part paper, we identify a broad class of decentralized
output-feedback LQG systems for which the optimal control strategies have a
simple intuitive estimation structure and can be computed efficiently. Roughly,
we consider the class of systems for which the coupling of dynamics among
subsystems and the inter-controller communication is characterized by the same
directed graph. Furthermore, this graph is assumed to be a multitree, that is,
its transitive reduction can have at most one directed path connecting each
pair of nodes. In this first part, we derive sufficient statistics that may be
used to aggregate each controller's growing available information. Each
controller must estimate the states of the subsystems that it affects (its
descendants) as well as the subsystems that it observes (its ancestors). The
optimal control action for a controller is a linear function of the estimate it
computes as well as the estimates computed by all of its ancestors. Moreover,
these state estimates may be updated recursively, much like a Kalman filter
On resilient control of dynamical flow networks
Resilience has become a key aspect in the design of contemporary
infrastructure networks. This comes as a result of ever-increasing loads,
limited physical capacity, and fast-growing levels of interconnectedness and
complexity due to the recent technological advancements. The problem has
motivated a considerable amount of research within the last few years,
particularly focused on the dynamical aspects of network flows, complementing
more classical static network flow optimization approaches. In this tutorial
paper, a class of single-commodity first-order models of dynamical flow
networks is considered. A few results recently appeared in the literature and
dealing with stability and robustness of dynamical flow networks are gathered
and originally presented in a unified framework. In particular, (differential)
stability properties of monotone dynamical flow networks are treated in some
detail, and the notion of margin of resilience is introduced as a quantitative
measure of their robustness. While emphasizing methodological aspects --
including structural properties, such as monotonicity, that enable tractability
and scalability -- over the specific applications, connections to
well-established road traffic flow models are made.Comment: accepted for publication in Annual Reviews in Control, 201
Decentralized pole assignment for interconnected systems
Given a general proper interconnected system,
this paper aims to design a LTI decentralized controller to
place the modes of the closed-loop system at pre-determined
locations. To this end, it is first assumed that the structural
graph of the system is strongly connected. Then, it is shown
applying generic static local controllers to any number of
subsystems will not introduce new decentralized fixed modes
(DFM) in the resultant system, although it has fewer inputoutput
stations compared to the original system. This means
that if there are some subsystems whose control costs are
highly dependent on the complexity of the control law, then
generic static controllers can be applied to such subsystems,
without changing the characteristics of the system in terms of
the fixed modes. As a direct application of this result, in the
case when the system has no DFMs, one can apply generic static
controllers to all but one subsystem, and the resultant system
will be controllable and observable through that subsystem.
Now, a simple observer-based local controller corresponding to
this subsystem can be designed to displace the modes of the
entire system arbitrarily. Similar results can also be attained
for a system whose structural graph is not strongly connected.
It is worth mentioning that similar concepts are deployed in the
literature for the special case of strictly proper systems, but as
noted in the relevant papers, extension of the results to general
proper systems is not trivial. This demonstrates the significance
of the present work
Distributed Robust Set-Invariance for Interconnected Linear Systems
We introduce a class of distributed control policies for networks of
discrete-time linear systems with polytopic additive disturbances. The
objective is to restrict the network-level state and controls to user-specified
polyhedral sets for all times. This problem arises in many safety-critical
applications. We consider two problems. First, given a communication graph
characterizing the structure of the information flow in the network, we find
the optimal distributed control policy by solving a single linear program.
Second, we find the sparsest communication graph required for the existence of
a distributed invariance-inducing control policy. Illustrative examples,
including one on platooning, are presented.Comment: 8 Pages. Submitted to American Control Conference (ACC), 201
On the Limited Communication Analysis and Design for Decentralized Estimation
This paper pertains to the analysis and design of decentralized estimation
schemes that make use of limited communication. Briefly, these schemes equip
the sensors with scalar states that iteratively merge the measurements and the
state of other sensors to be used for state estimation. Contrarily to commonly
used distributed estimation schemes, the only information being exchanged are
scalars, there is only one common time-scale for communication and estimation,
and the retrieval of the state of the system and sensors is achieved in
finite-time. We extend previous work to a more general setup and provide
necessary and sufficient conditions required for the communication between the
sensors that enable the use of limited communication decentralized
estimation~schemes. Additionally, we discuss the cases where the sensors are
memoryless, and where the sensors might not have the capacity to discern the
contributions of other sensors. Based on these conditions and the fact that
communication channels incur a cost, we cast the problem of finding the minimum
cost communication graph that enables limited communication decentralized
estimation schemes as an integer programming problem.Comment: Updates on the paper in CDC 201
HOMEBOTS: Intelligent Decentralized Services for Energy Management
The deregulation of the European energy market, combined with emerging advanced capabilities of information technology, provides strategic opportunities for new knowledge-oriented services on the power grid. HOMEBOTS is the namewe have coined for one of these innovative services: decentralized power load management at the customer side, automatically carried out by a `society' of interactive household, industrial and utility equipment. They act as independent intelligent agents that communicate and negotiate in a computational market economy. The knowledge and competence aspects of this application are discussed, using an improved \ud
version of task analysis according to the COMMONKADS knowledge methodology. Illustrated by simulation results, we indicate how customer knowledge can be mobilized to achieve joint goals of cost and energy savings. General implications for knowledge creation and its management are discussed
Elastic Business Process Management: State of the Art and Open Challenges for BPM in the Cloud
With the advent of cloud computing, organizations are nowadays able to react
rapidly to changing demands for computational resources. Not only individual
applications can be hosted on virtual cloud infrastructures, but also complete
business processes. This allows the realization of so-called elastic processes,
i.e., processes which are carried out using elastic cloud resources. Despite
the manifold benefits of elastic processes, there is still a lack of solutions
supporting them.
In this paper, we identify the state of the art of elastic Business Process
Management with a focus on infrastructural challenges. We conceptualize an
architecture for an elastic Business Process Management System and discuss
existing work on scheduling, resource allocation, monitoring, decentralized
coordination, and state management for elastic processes. Furthermore, we
present two representative elastic Business Process Management Systems which
are intended to counter these challenges. Based on our findings, we identify
open issues and outline possible research directions for the realization of
elastic processes and elastic Business Process Management.Comment: Please cite as: S. Schulte, C. Janiesch, S. Venugopal, I. Weber, and
P. Hoenisch (2015). Elastic Business Process Management: State of the Art and
Open Challenges for BPM in the Cloud. Future Generation Computer Systems,
Volume NN, Number N, NN-NN., http://dx.doi.org/10.1016/j.future.2014.09.00
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