534 research outputs found
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
South Pole Telescope Software Systems: Control, Monitoring, and Data Acquisition
We present the software system used to control and operate the South Pole
Telescope. The South Pole Telescope is a 10-meter millimeter-wavelength
telescope designed to measure anisotropies in the cosmic microwave background
(CMB) at arcminute angular resolution. In the austral summer of 2011/12, the
SPT was equipped with a new polarization-sensitive camera, which consists of
1536 transition-edge sensor bolometers. The bolometers are read out using 36
independent digital frequency multiplexing (\dfmux) readout boards, each with
its own embedded processors. These autonomous boards control and read out data
from the focal plane with on-board software and firmware. An overall control
software system running on a separate control computer controls the \dfmux
boards, the cryostat and all other aspects of telescope operation. This control
software collects and monitors data in real-time, and stores the data to disk
for transfer to the United States for analysis
Visualizing Sensor Network Coverage with Location Uncertainty
We present an interactive visualization system for exploring the coverage in
sensor networks with uncertain sensor locations. We consider a simple case of
uncertainty where the location of each sensor is confined to a discrete number
of points sampled uniformly at random from a region with a fixed radius.
Employing techniques from topological data analysis, we model and visualize
network coverage by quantifying the uncertainty defined on its simplicial
complex representations. We demonstrate the capabilities and effectiveness of
our tool via the exploration of randomly distributed sensor networks
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