734,560 research outputs found
Interfacing to Time-Triggered Communication Systems
Time-triggered communication facilitates the construction of multi-component real-time systems whose components are in control of their temporal behavior. However, the interface of a time-triggered communication system has to be accessed with care, to avoid that the temporal independence of components gets lost. This paper shows two interfacing strategies, one for asynchronous interface access (in two variants, one being the new Rate-Bounded Non-Blocking Communication protocol) and one for time-aware, synchronized interface access, that allow components to maintain temporal independence. The paper describes and compares the interfacing strategies.Final Accepted Versio
Specifying multimedia configurations in Z
In this paper we illustrate how the formal specification language Z can be used to reason about the temporal and throughput constraints associated with multimedia flows of information. In particular we show how it is possible to specify issues related to maximum delays, throughputs and jitter of information flows and how control of these flows can be achieved. What makes our work particularly interesting is that we deal with temporal aspects of systems without the use of a temporal logic. Rather, we highlight the versatility of the Z language in modelling systems with real time constraints
Receding Horizon Temporal Logic Control for Finite Deterministic Systems
This paper considers receding horizon control of finite deterministic
systems, which must satisfy a high level, rich specification expressed as a
linear temporal logic formula. Under the assumption that time-varying rewards
are associated with states of the system and they can be observed in real-time,
the control objective is to maximize the collected reward while satisfying the
high level task specification. In order to properly react to the changing
rewards, a controller synthesis framework inspired by model predictive control
is proposed, where the rewards are locally optimized at each time-step over a
finite horizon, and the immediate optimal control is applied. By enforcing
appropriate constraints, the infinite trajectory produced by the controller is
guaranteed to satisfy the desired temporal logic formula. Simulation results
demonstrate the effectiveness of the approach.Comment: Technical report accompanying a paper to be presented at ACC 201
A timeband framework for modelling real-time systems
Complex real-time systems must integrate physical processes with digital control, human operation and organisational structures. New scientific foundations are required for specifying, designing and implementing these systems. One key challenge is to cope with the wide range of time scales and dynamics inherent in such systems. To exploit the unique properties of time, with the aim of producing more dependable computer-based systems, it is desirable to explicitly identify distinct time bands in which the system is situated. Such a framework enables the temporal properties and associated dynamic behaviour of existing systems to be described and the requirements for new or modified systems to be specified. A system model based on a finite set of distinct time bands is motivated and developed in this paper
Automatic Estimation of the Exposure to Lateral Collision in Signalized Intersections using Video Sensors
Intersections constitute one of the most dangerous elements in road systems.
Traffic signals remain the most common way to control traffic at high-volume
intersections and offer many opportunities to apply intelligent transportation
systems to make traffic more efficient and safe. This paper describes an
automated method to estimate the temporal exposure of road users crossing the
conflict zone to lateral collision with road users originating from a different
approach. This component is part of a larger system relying on video sensors to
provide queue lengths and spatial occupancy that are used for real time traffic
control and monitoring. The method is evaluated on data collected during a real
world experiment
Agent Based Approaches to Engineering Autonomous Space Software
Current approaches to the engineering of space software such as satellite
control systems are based around the development of feedback controllers using
packages such as MatLab's Simulink toolbox. These provide powerful tools for
engineering real time systems that adapt to changes in the environment but are
limited when the controller itself needs to be adapted.
We are investigating ways in which ideas from temporal logics and agent
programming can be integrated with the use of such control systems to provide a
more powerful layer of autonomous decision making. This paper will discuss our
initial approaches to the engineering of such systems.Comment: 3 pages, 1 Figure, Formal Methods in Aerospac
Controlling extended systems with spatially filtered, time-delayed feedback
We investigate a control technique for spatially extended systems combining
spatial filtering with a previously studied form of time-delay feedback. The
scheme is naturally suited to real-time control of optical systems. We apply
the control scheme to a model of a transversely extended semiconductor laser in
which a desirable, coherent traveling wave state exists, but is a member of a
nowhere stable family. Our scheme stabilizes this state, and directs the system
towards it from realistic, distant and noisy initial conditions. As confirmed
by numerical simulation, a linear stability analysis about the controlled state
accurately predicts when the scheme is successful, and illustrates some key
features of the control including the individual merit of, and interplay
between, the spatial and temporal degrees of freedom in the control.Comment: 9 pages REVTeX including 7 PostScript figures. To appear in Physical
Review
Shaping Pulses to Control Bistable Biological Systems
In this paper we study how to shape temporal pulses to switch a bistable
system between its stable steady states. Our motivation for pulse-based control
comes from applications in synthetic biology, where it is generally difficult
to implement real-time feedback control systems due to technical limitations in
sensors and actuators. We show that for monotone bistable systems, the
estimation of the set of all pulses that switch the system reduces to the
computation of one non-increasing curve. We provide an efficient algorithm to
compute this curve and illustrate the results with a genetic bistable system
commonly used in synthetic biology. We also extend these results to models with
parametric uncertainty and provide a number of examples and counterexamples
that demonstrate the power and limitations of the current theory. In order to
show the full potential of the framework, we consider the problem of inducing
oscillations in a monotone biochemical system using a combination of temporal
pulses and event-based control. Our results provide an insight into the
dynamics of bistable systems under external inputs and open up numerous
directions for future investigation.Comment: 14 pages, contains material from the paper in Proc Amer Control Conf
2015, (pp. 3138-3143) and "Shaping pulses to control bistable systems
analysis, computation and counterexamples", which is due to appear in
Automatic
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