20,403 research outputs found
Supervisor Localization of Discrete-Event Systems based on State Tree Structures
Recently we developed supervisor localization, a top-down approach to
distributed control of discrete-event systems in the Ramadge-Wonham supervisory
control framework. Its essence is the decomposition of monolithic (global)
control action into local control strategies for the individual agents. In this
paper, we establish a counterpart supervisor localization theory in the
framework of State Tree Structures, known to be efficient for control design of
very large systems. In the new framework, we introduce the new concepts of
local state tracker, local control function, and state-based local-global
control equivalence. As before, we prove that the collective localized control
behavior is identical to the monolithic optimal (i.e. maximally permissive) and
nonblocking controlled behavior. In addition, we propose a new and more
efficient localization algorithm which exploits BDD computation. Finally we
demonstrate our localization approach on a model for a complex semiconductor
manufacturing system
Attack-Resilient Supervisory Control of Discrete-Event Systems
In this work, we study the problem of supervisory control of discrete-event
systems (DES) in the presence of attacks that tamper with inputs and outputs of
the plant. We consider a very general system setup as we focus on both
deterministic and nondeterministic plants that we model as finite state
transducers (FSTs); this also covers the conventional approach to modeling DES
as deterministic finite automata. Furthermore, we cover a wide class of attacks
that can nondeterministically add, remove, or rewrite a sensing and/or
actuation word to any word from predefined regular languages, and show how such
attacks can be modeled by nondeterministic FSTs; we also present how the use of
FSTs facilitates modeling realistic (and very complex) attacks, as well as
provides the foundation for design of attack-resilient supervisory controllers.
Specifically, we first consider the supervisory control problem for
deterministic plants with attacks (i) only on their sensors, (ii) only on their
actuators, and (iii) both on their sensors and actuators. For each case, we
develop new conditions for controllability in the presence of attacks, as well
as synthesizing algorithms to obtain FST-based description of such
attack-resilient supervisors. A derived resilient controller provides a set of
all safe control words that can keep the plant work desirably even in the
presence of corrupted observation and/or if the control words are subjected to
actuation attacks. Then, we extend the controllability theorems and the
supervisor synthesizing algorithms to nondeterministic plants that satisfy a
nonblocking condition. Finally, we illustrate applicability of our methodology
on several examples and numerical case-studies
Supervisory Control for Behavior Composition
We relate behavior composition, a synthesis task studied in AI, to
supervisory control theory from the discrete event systems field. In
particular, we show that realizing (i.e., implementing) a target behavior
module (e.g., a house surveillance system) by suitably coordinating a
collection of available behaviors (e.g., automatic blinds, doors, lights,
cameras, etc.) amounts to imposing a supervisor onto a special discrete event
system. Such a link allows us to leverage on the solid foundations and
extensive work on discrete event systems, including borrowing tools and ideas
from that field. As evidence of that we show how simple it is to introduce
preferences in the mapped framework
Distributed Supervisory Control of Discrete-Event Systems with Communication Delay
This paper identifies a property of delay-robustness in distributed
supervisory control of discrete-event systems (DES) with communication delays.
In previous work a distributed supervisory control problem has been
investigated on the assumption that inter-agent communications take place with
negligible delay. From an applications viewpoint it is desirable to relax this
constraint and identify communicating distributed controllers which are
delay-robust, namely logically equivalent to their delay-free counterparts. For
this we introduce inter-agent channels modeled as 2-state automata, compute the
overall system behavior, and present an effective computational test for
delay-robustness. From the test it typically results that the given delay-free
distributed control is delay-robust with respect to certain communicated
events, but not for all, thus distinguishing events which are not
delay-critical from those that are. The approach is illustrated by a workcell
model with three communicating agents
Small cities face greater impact from automation
The city has proven to be the most successful form of human agglomeration and
provides wide employment opportunities for its dwellers. As advances in
robotics and artificial intelligence revive concerns about the impact of
automation on jobs, a question looms: How will automation affect employment in
cities? Here, we provide a comparative picture of the impact of automation
across U.S. urban areas. Small cities will undertake greater adjustments, such
as worker displacement and job content substitutions. We demonstrate that large
cities exhibit increased occupational and skill specialization due to increased
abundance of managerial and technical professions. These occupations are not
easily automatable, and, thus, reduce the potential impact of automation in
large cities. Our results pass several robustness checks including potential
errors in the estimation of occupational automation and sub-sampling of
occupations. Our study provides the first empirical law connecting two societal
forces: urban agglomeration and automation's impact on employment
Safe Environmental Envelopes of Discrete Systems
A safety verification task involves verifying a system against a desired
safety property under certain assumptions about the environment. However, these
environmental assumptions may occasionally be violated due to modeling errors
or faults. Ideally, the system guarantees its critical properties even under
some of these violations, i.e., the system is \emph{robust} against
environmental deviations. This paper proposes a notion of \emph{robustness} as
an explicit, first-class property of a transition system that captures how
robust it is against possible \emph{deviations} in the environment. We modeled
deviations as a set of \emph{transitions} that may be added to the original
environment. Our robustness notion then describes the safety envelope of this
system, i.e., it captures all sets of extra environment transitions for which
the system still guarantees a desired property. We show that being able to
explicitly reason about robustness enables new types of system analysis and
design tasks beyond the common verification problem stated above. We
demonstrate the application of our framework on case studies involving a
radiation therapy interface, an electronic voting machine, a fare collection
protocol, and a medical pump device.Comment: Full version of CAV23 pape
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