Distributed sensor Webs typically operate in dynamic environments where operating conditions, transient phenomena, availability of resources, and network connection quality change frequently and unpredictably. Often these changes can neither be completely anticipated nor accurately described during development or deployment. Our prior work has described how we developed agents and services that are capable of monitoring these changing conditions and adapting system parameters using the CORBA component model (CCM) deployment infrastructure as part of the multiagent architecture for coordinated responsive observations (MACRO) platform. Our recent application of MACRO to the South East Alaska monitoring network for Science, Telecommunications, Education, and Research (SEAMONSTER) project has identified new distributed deployment infrastructure challenges common to computationally constrained field environments in adaptive sensor Webs. These challenges include standardized execution of low-level hardware-dependent actions and on-going data tasks, automated provisioning of agents for heterogeneous field hardware, and minimizing deployment infrastructure overhead. This paper describes how we extended MACRO to address these sensor Web challenges by creating an action/effector framework standardizing the execution of lightweight actions and providing for automated provisioning of MACRO agents, in addition to footprint optimizations to the underlying CCM infrastructure.
This paper provides a passivity based framework to synthesize lm2-stable digital control networks in which m strictly-output passive controllers can control n−m strictly-output passive plants. The communication between the plants and controllers can tolerate time varying delay and data dropouts. In particular, we introduce a power junction which allows even a single controller (typically designed to control a single plant) to accurately control the output of multiple plants even if the corresponding dynamics of each plant is different. In addition to the power-junction we also introduce a passive downsampler (PDS) and passive upsampler (PUS) in order to further reduce networking traffic. A detailed (soft real-time) set of examples shows the tracking performance of the networked control system.
Model-based development methodologies are gaining ground as software applications are getting more and more complex while the pressure to decrease time-to-market continually increase. Domain-specific modeling tools that support system analysis, simulation, and automatic code generation can increase productivity. However, most domain-specific model translators are still manually written. This paper presents a technique that automatically generates a domain-specific application programming interface from the same metamodels that are used to define the domain-specific modeling language itself. This facilitates the creation of domain-specific model translators by providing a high-level abstraction hiding all the cumbersome modeling tool-specific implementation details from the developer. The approach is illustrated using the Generic Modeling Environment and the Microsoft .NET C# language.
The paper introduces a novel technique for the bearing estimation of radio sources that can be used for the precise localization and/or tracking of RF tags such as wireless sensor nodes. It is well known that the bearing to a radio source can be estimated by an array of antennas typically arranged in a circular manner. The method is often referred to as Quasi-Doppler measurement. The disadvantage of the existing method is that the receiver is relatively large because of the multiple antennas (typically 8 or 16) and it is computationally intensive to process the high frequency radio signals. Thus, it cannot be done on small, inexpensive radio tags. Instead, we propose to use the array on the transmitter side utilizing as few as three antennas. We use a radio interferometric technique to transform the useful phase information from the high frequency radio signal to a low frequency signal (< 1 kHz) that can be processed on low-cost hardware. Utilizing three anchors nodes with small antenna arrays, any number of low cost wireless nodes with single antennas can be accurately localized.
Probabilistic system models are useful for analyzing systems which operate under the presence of uncertainty. In this paper, we present a proposed technique for verifying certain safety and liveness properties for probabilistic timed automata. The proposed technique is an extension of a technique used to verify stochastic hybrid automata using an approximation with Markov Decision Processes. A case study for CSMA/CD protocol has been used to show case the methodology used in our technique.
High-confidence embedded real-time designs stretch the demands placed on design and development tools. We will demonstrate the design and testing of an embedded control system built using the ESMoL modeling language and supporting tools. ESMoL adds distributed deployment concepts to Simulink designs, and integrates scheduling analysis as well as platformspecific simulation. The testing system includes a simulated physical plant running in a hardware-in-the-loop configuration with the actual embedded controller.
Abstract-Virtual evaluation of complex command and control concepts demands the use of heterogeneous simulation environments. Development challenges include how to integrate multiple simulation platforms with varying semantics and how to integrate simulation models and the complex interactions between them. While existing simulation frameworks may provide many of the required services needed to coordinate among multiple simulation platforms, they lack an overarching integration approach that connects and relates the semantics of heterogeneous domain models and their interactions. This paper outlines some of the challenges encountered in developing a command and control simulation environment and discusses our use of the GME meta-modeling tool-suite to create a model-based integration approach that allows for rapid synthesis of complex HLA-based simulation environments.
The rapidly increasing use of distributed architectures in constructing real-world systems has led to the urgent need for a sound systematic approach in designing networked control systems. Communication delays and other uncertainties complicate the development of these systems. This paper describes a prototype modeling language for the design of networked control systems using passive techniques to decouple the control design from network uncertainties. The modeling language includes an integrated analysis tool to check for passivity and a code generator for simulation in MATLAB/Simulink using the True-Time platform modeling toolbox. The resulting designs are more robust to platform e effects, without costly design verification.
Thermal control is crucial to real-time systems as excessive processor temperature can cause system failure or unacceptable performance degradation due to hardware throttling. Real-time systems face significant challenges in thermal management as they must avoid processor overheating while still delivering desired real-time performance. Furthermore, many real-time systems must handle a broad range of uncertainties in system and environmental conditions. To address these challenges, this paper presents Thermal Control under Utilization Bound (TCUB), a novel thermal control algorithm specifically designed for real-time systems. TCUB employs a feedback control loop that dynamically controls both processor temperature and CPU utilization through task rate adaptation. Rigorously modeled and designed based on control theory, TCUB can maintain both desired processor temperature and CPU utilization, thereby avoiding processor overheating and maintaining desired real-time performance. A salient feature of TCUB lies in its capability to handle a broad range of uncertainties in terms of processor power consumption, task execution times, ambient temperature, and unexpected thermal faults. The robustness of TCUB makes it particularly suitable for real-time embedded systems that must operate in highly unpredictable and hash environments. The advantages of TCUB have been demonstrated through extensive simulations under a broad range of system and environmental uncertainties. available: http://cse.wustl.edu/Research/Lists/Technical%20Reports/Attachments/867/tcub1.pdf (revised 10/2009)
The development of embedded software for highconfidence systems is a challenging task that must be supported by a deep integration of control theoretical and computational aspects. Model-based development of embedded software has been practiced for more than a decade now, but very few integrated approaches have emerged to provide end-to-end support for the process, and integrate platform aspects as well as verification. The paper describes an early version of a model-based prototyping toolchain that provides such support and covers most engineering steps. The toolchain is coupled with a hardware-in-the-loop simulation system, allowing quick experimental evaluation of designs.
Self-healing systems are considered as cognation-enabled sub form of fault tolerance system. But our experiments that we report in this paper show that self-healing systems can be used for performance optimization, configuration management, access control management and many other functions. The exponential complexity that results from interaction between autonomic systems and users (software and human users) has hindered the deployment and user of intelligent systems for some time. We show that if exceptional complexity is converted into self-growing knowledge, (policies in our case), can make up for the initial development cost of building an intelligent system. In this paper, we propose that AHSEN (Autonomic Healing-based Self management Engine) clearly demarcates the logical ambiguities in contemporary designs and shows its performance through empirical results obtained through experiments.
Modern Network Centric Operations drive the complexity of information fusion and command and control (C2) systems. Driving this complexity further is the interplay dynamics of the human element, information systems, and communication networks. The lack of low-cost realistic experimental context limits the testing, evaluation, and further development of fusion systems to small-scale localized experiments. A Model-based Integration and Experimentation Framework is proposed. This framework is built on C2 Wind Tunnel - a robust multi-model simulation framework for integrating simulations to drive fusion experiments. The second component of the framework is a model-based system of systems integration tool-suite that allows modeling, synthesis, and deployment of networked system of systems. This component enables researchers to embed their research algorithm into the networked C2 systems. The C2 Wind Tunnel has been used to execute several simulation-driven C2 Experiments.
Resilient control systems play a special role in the area of cyber-physical systems, where the design must address the question how complex dynamic plants are to be controlled safely and reliably when a control system is under a cyber attack. In this paper we describe a control theoretical framework based on the concept of passivity for designing a control network which can tolerate, for instance, denial-of-service attacks on networks used in the closed loop. In particular, we demonstrate how the resilient power junction structure could be applied, and provide simulated results.