Showing papers on "Cyber-physical system published in 2009"

Cyber-physical Systems

Abstract: Sophisticated control-computing codesign provides unprecedented performance and efficiency levels for cyber-physical systems.

Spatio-Temporal Event Model for Cyber-Physical Systems

Abstract: The emerging Cyber-Physical Systems (CPSs) are envisioned to integrate computation, communication and control with the physical world. Therefore, CPS requires close-interactions between the cyber and physical worlds both in time and space. These interactions are usually governed by events, which occur in the physical world and should autonomously be reflected in the cyber-world, and actions, which are taken by the CPS as a result of detection of events and certain decision mechanisms. Both event detection and action decision operations should be performed accurately and timely to guarantee temporal and spatial correctness. This calls for a flexible architecture and task representation framework to analyze CP operations. In this paper, we explore the temporal and spatial properties of events, define a novel CPS architecture, and develop a layered spatio-temporal event model for CPS. The event is represented as a function of attribute-based, temporal, and spatial event conditions. Moreover, logical operators are used to combine different types of event conditions to capture composite events. To the best of our knowledge, this is the first event model that captures the heterogeneous characteristics of CPS for formal temporal and spatial analysis.

Sensor Network Navigation without Locations

Abstract: We propose a pervasive usage of the sensor network infrastructure as a cyber-physical system for navigating internal users in locations of potential danger. Our proposed application differs from previous work in that they typically treat the sensor network as a media of data acquisition while in our navigation application, in-situ interactions between users and sensors become ubiquitous. In addition, human safety and time factors are critical to the success of our objective. Without any pre-knowledge of user and sensor locations, the design of an effective and efficient navigation protocol faces non-trivial challenges. We propose to embed a road map system in the sensor network without location information so as to provide users navigating routes with guaranteed safety. We accordingly design efficient road map updating mechanisms to rebuild the road map in the event of changes in dangerous areas. In this navigation system, each user only issues local queries to obtain their navigation route. The system is highly scalable for supporting multiple users simultaneously. We implement a prototype system with 36 TelosB motes to validate the effectiveness of this design. We further conduct comprehensive and large-scale simulations to examine the efficiency and scalability of the proposed approach under various environmental dynamics.

Cyber-Physical Systems: A New Frontier

Abstract: The report of the President's Council of Advisors on Science and Technology (PCAST) has placed CPS on the top of the priority list for federal research investment [6]. This article first reviews some of the challenges and promises of CPS, followed by an articulation of some specific challenges and promises that are more closely related to the sensor networks, ubiquitous and trustworthy computing conference.

A vision of cyber-physical internet

Abstract: When the Internet was born, the purpose was to interconnect computers to share digital data at large-scale. On the other hand, when embedded systems were born, the objective was to control system components under real-time constraints through sensing devices, typically at small to medium scales. With the great evolution of the Information and Communication Technology (ICT), the tendency is to enable ubiquitous and pervasive computing to control everything (physical processes and physical objects) anytime and at a large-scale. This new vision gave recently rise to the paradigm of Cyber-Physical Systems (CPS). In this position paper, we provide a realistic vision to the concept of the Cyber-Physical Internet (CPI), discuss its design requirements and present the limitations of the current networking abstractions to fulfill these requirements. We also debate whether it is more productive to adopt a system integration approach or a radical design approach for building large-scale CPS. Finally, we present a sample of realtime challenges that must be considered in the design of the Cyber-Physical Internet.

A General Framework for Quantitative Modeling of Dependability in Cyber-Physical Systems: A Proposal for Doctoral Research

Abstract: The overarching objective of the proposed doctoral researches to build a qualitative and quantitative understanding of dependability in cyber physical systems (CPS).The existing body of knowledge includes frameworks and techniques for assessment, modeling, and simulation of the physical and cyber infrastructures, respectively, but such isolated analysis is incapable of fully capturing the interdependencies between these infrastructures. Understanding these interdependencies is a critical precursor to accurate representation and modeling of the CPS as a whole, especially with respect to dependability.The physical water distribution infrastructure, coupled with the hardware and software that support intelligent water allocation, comprise the model CPS that will be used as a case study for the proposed research. A preliminary literature review has been carried out on dependability modeling for CPS, with very sparse results. Allocation algorithms for water distribution have also been investigated,with game theory appearing to hold the most promise.An agent-based approach is suggested for linking the cyber and physical layers, where the agents retrieve information from sensors monitoring the physical components and provide this information to the cyber components. Fault injection will be used to investigate the propagation of failures between the cyber and physical layers. Markovian models will be used to capture the manifestation of cyber and/or physical faults as failures in water allocation, or containment of contaminants.

Optimal Observation for Cyber-physical Systems: A Fisher-information-matrix-based Approach

Abstract: "Optimal Observation for Cyber-physical Systems" addresses the challenge, fundamental to the design of wireless sensor networks (WSNs), presented by the obligatory trade-off between precise estimates and system constraints. A unified theoretical framework, based on the well-established theory of optimal experimental design and providing consistent solutions to problems hitherto requiring a variety of approaches, is put forward to solve a large class of optimal observation problems. The Fisher information matrix plays a key role in this framework and makes it feasible to provide analytical solutions to some complex and important questions which could not be answered in the past. Readers with an applied background in WSN implementation will find all the understanding of the key theory of optimal experimental design they need within this book. The use of multiple examples to illustrate the theoretical parts of the book brings the subject into sharper focus than would an abstract theoretical disquisition.

Towards Integrated Simulation of Cyber-Physical Systems: A Case Study on Intelligent Water Distribution

Abstract: In cyber-physical systems (CPSs), embedded computing systems and communication capability are used to streamline and fortify the operation of a physical system. Intelligent critical infrastructure systems are among the most important CPSs and also prime examples of pervasive computing systems, as they exploit computing to provide "anytime, anywhere" transparent services. The existing body of knowledge includes techniques for assessment, modeling, and simulation of physical and cyber infrastructures, respectively, but such isolated analysis is incapable of fully capturing the interdependencies that occur when they intertwine to create a CPS. Fundamental differences exist between the attributes of cyber and physical components, significantly complicating representation of their behavior with a single comprehensive model or simulation tool. This paper articulates the challenges present in integrated simulation of a CPS, where the goal is to accurately reflect the operation and interaction of the cyber and physical networks that comprise the system. A solution is presented for the CPS domain of intelligent water distribution networks, using EPANET and Matlab to represent the physical water distribution network and the decision support algorithms used to control the allocation of water, respectively.

Study on the Architecture and Associated Technologies for Internet of Things

Abstract: The technology of the Internet of Things (IOT) has attracted highly attention of academia,industry,and news media.There are still many open issues in the definition,internal principles,architectures and system models of IOT.Through the analysis of current technical materials and application cases of IOT,this paper discusses the relations between Next Generation Network,Cyber-Physical Systems,Wireless Sensor Network and the IOT.It proposes service types and node classification of IOT and designs the architecture and system model of IOT based on passive,active and internet nodes structure of IOT.After summary of the features of IOT,it proposes the suggestions on the researches and development of IOT.

An Architectural Approach to the Design and Analysis of Cyber-Physical Systems

Abstract: This paper presents an extension of existing software architecture tools to model physical systems, their interconnections, and the interactions between physical and cyber components. A new CPS architectural style is introduced to support the principled design and evaluation of alternative architectures for cyber-physical systems (CPSs). The implementation of the CPS architectural style in AcmeStudio includes behavioral annotations on components and connectors using either finite state processes (FSP) or linear hybrid automata (LHA) with plug-ins to perform behavior analysis using the Labeled Transition System Analyzer (LTSA) or Polyhedral Hybrid Automata Verifier (PHAVer), respectively. The CPS architectural style and analysis plug-ins are illustrated with an example.

Challenges of implementing cyber-physical security solutions in body area networks

Abstract: Cyber-physical approach to securing Body Area Networks (BANs) provides solutions that are plug-n-play and transparent to its users. These Cyber-Physical Security Solutions (CPSS) actively involve characteristics from the physical environment. As a result they require a combination of signal processing (to extract features from the physical environment) and security primitives to function. In this paper we outline some of our experiences while implementing Plethysmogram based Key Agreement (PKA) - a CPSS - that uses Photoplethysmogram (PPG) based features for key agreement. Given the limited capabilities (computation, memory, power) of individual sensor nodes in a BAN, implementing CPSS for them is challenging. We therefore design Field Programmable Gate Array (FPGA) based hardware add-on for sensor nodes in a BAN, dedicated to execute PKA. The main contributions of this work are: 1) description of our experiences in implementation of PKA on FPGA platform; 2) identification of the design goals and trade-offs for validating implementation of CPSS; and 3) a discussion on the feasibility of a software implementation of PKA based on our experience gained from the FPGA prototyping.

Toward a Smart Cyber-Physical Space: A Context-Sensitive Resource-Explicit Service Model

Abstract: Cyber-Physical Systems (CPSs) are combinations of physical devices controlled by software systems to accomplish specified tasks under stringent real-time and physical resource constraints. The major benefit of these systems lies in their potentially positive impacts on real world systems by enabling high dependability assurance. However, a key challenge is to determine not only correct but also cost-effective dynamic operation of all physical devices in the system in the context of real world constraints.In this paper, we present a novel context-sensitive resource-explicit service model and develop the corresponding composition formalisms to help automate the composition process under real-time constraints as well as under various physical resource constraints. The approach is illustrated using an emergency response system.

Model-Checking BNDC Properties in Cyber-Physical Systems

Abstract: In Cyber-physical systems, which are the integrations of computational and physical processes, it is hard to realize certain security properties. Fundamentally, physically observable behavior leads to violations of confidentiality. We focus on analyzing certain non-interference based security properties to ensure that interactions between the cyber and physical processes preserve confidentiality. A considerable barrier to this analysis is representing the physical system’s interactions. In this paper, these physical system properties are encoded into a discrete event system and the combined Cyber-physical system is described using the process algebra SPA. The model checker, CoPS shows BNDC (Bisimulation based Non Deducibility on Compositions) properties,which are a variant of non-interference properties, to check the system’s security against all high level potential interactions. We consider a model problem of invariant pipeline flow to examine the BNDC properties and their applicability for cyber-physical systems.

Extending service model to build an effective service composition framework for cyber-physical systems

Abstract: Cyber-Physical Systems (CPSs) are combinations of physical entities controlled by software systems to accomplish specified tasks under stringent real-time and physical entity constraints. As more and more physical entities are equipped with embedded computers, they are becoming more and more intelligent. However, the problem of effectively composing the services provided by cyber and physical entities to achieve specific goals still remains a challenge. Traditional service-oriented models and composition techniques are insufficient for CPS. In this paper, we present a novel Physical-Entity (PE) service-oriented model to address the problem, including the concepts of PE-ontology and PE-SOA specifications. Based on the model, we develop a two-level compositional reasoning approach, which divides the process into abstract and physical levels to expedite the composition process. With the assistance of the PE-ontology and PE-SOA, abstract level reasoning is performed by hiding the physical level details. This separation greatly reduces the search space for both levels through a divide-and-conquer technique. The model and the composition approach are illustrated using a simplified emergency response case study system.

Towards Configurable Real-Time Hybrid Structural Testing: A Cyber-Physical System Approach

Abstract: Real-time hybrid testing of civil structures represents agrand challenge in the emerging area of cyber-physical systems. Hybrid testing improves significantly on either purely numerical or purely empirical approaches by integrating physical structural components and computational models. Actuator dynamics, complex interactions among computers and physical components, and computation and communication delays all hamper the ability to conduct accurate tests. To address these challenges, this paper presents initial work towards a Cyber-physical Instrument for Real-time hybrid Structural Testing (CIRST). CIRST aims to provide two salient features: a highly configurable architecture for integrating computers and physical components; and system support for real-time operations in distributed hybrid testing. This paper presents the motivation of the CIRST architectureand preliminary test results from a proof-of-concept implementation that integrates a simple structural element and simulation model. CIRST will have broad impacts on thefields of both civil engineering and real-time computing.It will enable high-fidelity real-time hybrid testing of awide range of civil infrastructures, and will also providea high-impact cyber-physical application for the study andevaluation of real-time middleware.

Reliability Analysis for the Advanced Electric Power Grid: From Cyber Control and Communication to Physical Manifestations of Failure

Abstract: The advanced electric power grid is a cyber-physical system comprised of physical components, such as transmission lines and generators, and a network of embedded systems deployed for their cyber control. The objective of this paper is to qualitatively and quantitatively analyze the reliability of this cyber-physical system. The original contribution of the approach lies in the scope of failures analyzed, which crosses the cyber-physical boundary by investigating physical manifestations of failures in cyber control. As an example of power electronics deployed to enhance and control the operation of the grid, we study Flexible AC Transmission System (FACTS) devices, which are used to alter the flow of power on specific transmission lines. Through prudent fault injection, we enumerate the failure modes of FACTS devices, as triggered by their embedded software, and evaluate their effect on the reliability of the device and the reliability of the power grid on which they are deployed. The IEEE118 bus system is used as our case study, where the physical infrastructure is supplemented with seven FACTS devices to prevent the occurrence of four previously documented potential cascading failures.

Optimal Adaptive System Health Monitoring and Diagnosis for Resource Constrained Cyber-Physical Systems

Abstract: Cyber-physical systems (CPS) are complex net-centric hardware/software systems that can be applied to transportation, healthcare, defense, and other real-time applications. To meet the high reliability and safety requirements for these systems, proactive system health monitoring and management (HMM) techniques can be used. However, to be effective, it is necessary to ensure that the operation of the underlying HMM system does not adversely impact the normal operation of the system being monitored. In particular, it must be ensured that the operation of the HMM system will not lead to resource contentions that may prevent the system being monitored from timely completion of critical tasks. This paper presents an adaptive HMM system model that defines the fault diagnosis quality metrics and supports diagnosis requirement specifications. Based on the model, the sensor activation decision problem (SADP) is defined along with a steepest descent based heuristic algorithm to make the HMM configuration decisions that best satisfy the diagnosis quality requirements. Evaluation results show that the technique reduces the overall system resource consumption without adversely impacting the diagnosis capability of the HMM.

Security solutions for cyber-physical systems

Abstract: Cyber-Physical Systems (CPS) are sensing, communication and processing platforms, deeply embedded in physical processes and provide real-time monitoring and actuation services. Such systems are becoming increasing common in enabling many of the pervasive computing technologies that are becoming available today such as, smart-homes, smart-vehicles, pervasive health monitoring systems. Given the automation that CPSs introduce in managing physical processes, and the detail of information available to them for carrying out their tasks, securing them is of prime importance. In this dissertation, a novel security paradigm for CPSs is proposed, called Cyber-Physical Security (CYPSec). CYPSec solutions are unique in that they take they take into account the environmentally-coupled nature of CPSs in enabling security solutions. This dissertation explores CYPSec solutions for two diverse but related problems. The first is a usable and secure key agreement protocol called Physiological Signal based Key Agreement (PSKA), which combines signal processing and cryptographic primitives to enable automated key agreement between sensors in a Body Area Network (BAN) without any form of external user involvement. It uses specific physiological stimuli-based features (Photoplethsymogram and Electrocardiogram) from the human body for its task. The second is an access control model called Criticality Aware Access Control (CAAC), which facilitates a more adaptive and proactive provisioning of authorizations—provide the right set of privileges for the right set of subjects, at the right time for the right duration - for managing emergencies within smart-infrastructures. The following are the principal contributions of this dissertation: (1) a novel CYPSec solution for BANs (PSKA) - which combines physiological signal processing and cryptographic primitives for securing inter-sensor communication; (2) a benchmark of PSKA using Matlab to demonstrate its correctness and usable security design goal; (3) successful prototype of PSKA on Crossbow Mote platform as a part of Ayushman pervasive health monitoring test-bed, to demonstrate its viability on resource-constrained platforms in terms of computation, communication, memory and energy consumption requirements; (4) a CYPSec access control model for smart-infrastructures (CAAC)—which can facilitate dynamic and proactive emergency management by temporarily providing the required privileges to users without their explicit request; (5) a detailed formalization of CAAC, along with description of its policy specifications, and an example usage scenario on a smart-oil rig platform; and; (6) a prototype of CAAC as a part of the Ayushman test-bed to demonstrate its proactivity and adaptiveness design goals.

A unifying specification logic for cyber-physical systems

Abstract: The varieties of possible interaction between computational systems and physical environments is at the heart of a new modeling paradigm called cyber-physical systems. In order to model and control these interactions it necessary to present the fundamental properties of physical environments in a formalism compatible with the computational structures, usually in a formal logic or an algebraic calculus. In this paper, we propose a model as a step towards reasoning about the problems of uncertainty and surprise in the context of cyber-physical systems operating under mixed human/autonomous control. In controlling embedded devices, human operators are, in most cases, assisted by automated controllers (like driving assistance systems and automatic pilots). A new issue appeared in many applications is to model the automatic controllers which are user centric, i.e. the controllers are carrying a runtime monitoring of the system behaviour in its environment, they inform and warn the user on safety hazardous situation and they take action only when the user fails to react. A robust controller should be able to operate in open, random environments and to assist the human operator in case of appearance of surprising, possible catastrophic situations.

Situation based control for cyber-physical environments

Abstract: The use of event-based paradigms to handle control problems in cyber-physical environments is of critical research importance. Most current works however provide partial solutions by only considering individual aspects like event detection, temporal calculi or signal based control. There is thus a need to define a new problem of situation based control which supports symbolic reasoning, strong temporal support and explicit inclusion of domain knowledge to undertake intelligent control in dynamic environments. We describe the problem from a traditional control theoretic perspective and show how it can be handled in practice using the semantics of ‘Situation Calculus’. The motivations for future research as well as the research challenges have been identified. The use of the proposed approach to support emerging cyber-physical applications is demonstrated through the example of a multimodal tele-presence application involving selection of appropriate sensor and actuator parameters based on exogenous user actions.

Time-Centric Models For Designing Embedded Cyber-physical Systems

Abstract: : The problem addressed by this paper is that real-time embedded software today is commonly built using programming abstractions with little or no temporal semantics. The focus is on computer-based systems where multiple computers are connected on a network and interact with and through physical processes (the plant) via sensors and actuators. Such systems are often termed cyber-physical systems (CPS). The paper discusses the use of an extension to the Ptolemy II framework as a coordination language for the design of distributed real-time embedded systems. Specifically, the paper shows how to use modal models in the context of the PTIDES extension of Ptolemy II to provide a firm basis for the design of an important class of problems. Several examples are given to show the use of this environment in the design of interesting practical real-time systems.

An Approach to Middleware Specialization for Cyber Physical Systems

Abstract: Contemporary computing infrastructure, such as networking stacks, OS and middleware, are made up of layers of software functionality that have evolved over decades to support the broadest range of applications.The feature-richness and the layers of functionality, however, tend to be excessive and a source of performance overhead for Cyber-physical Systems (CPS). Yet it is necessary to leverage the decades of proven patterns and principles in these infrastructures. This paper presents an approach to systematically specialize general-purpose middleware used to host CPS. Our approach is based on the principles of Feature-Oriented Software Development(FOSD), which requires deducing an algebraic structure of contemporary middleware based on a higher level of abstraction of features. The paper showcase how Origami matrices and generative programming can play a key role in realizing the specializations. The paper concludes by delving in to future open areas of middleware specialization research.

A passivity-based framework for resilient cyber physical systems

Abstract: 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.

Joint Sleep Scheduling and Mode Assignment in Wireless Cyber-Physical Systems

Abstract: Recent years have witnessed the deployment of wireless Cyber-Physical Systems(CPS) for a variety of important applications.A key requirement for wireless CPS systems is to sustain a long lifetime on limited power supplies. At the same time, due to the criticality of CPS applications, many computation and communication tasks must be finished within timing constraints to avoid undesirable or even catastrophic consequences.%%Minimizing network-wide energy consumption is a key issue in designing%cyber-physical systems.While a lot of work has been done to manage energy consumption on single processor real-time systems,little work has been done in network-wide energy consumption management for real-time applications.Existing work on network-wide energy minimization assumes that the underlying network is always connected, which is not consistent with the practice in which wireless nodes often turn off their network interfaces in a sleep schedule to reduce energy consumption.%Moreover, existing sleep scheduling techniques are unaware of computation status and often%lead to unnecessary wakeup overhead.%In this paper, we propose solutions to minimize%network-wide energy consumption for real-time tasks with precedence%constraints executing on wireless cyber-physical systems.This paper jointly considers the radio sleep scheduling of wireless nodes and the execution modes of processors. Based on wireless network topologies, different schemes are proposed to minimize energy consumption while guaranteeing the timing and precedence constraints. When the precedence graph is a tree, optimal result on energy management is achieved. The experiments show that our approach significantly reduces total energy consumption compared with the previous work.

A cyber-physical middleware framework for continuous monitoring of water distribution systems

Abstract: The middleware for a cyber-physical system is crucial as it tightly integrates computation with physical processes to achieve better reliability, distributed coordination, higher precision and efficiency, and better autonomous control. In this work, we design and develop the cyber-physical middleware framework for a large-scale water distribution system monitoring effort.

An Integrated Specification Logic for Cyber-Physical Systems

Abstract: Cyber-physical systems denote a new modeling paradigm that promotes a holistic view on complex systems. These systems have been studied before from various particular perspectives using paradigms like ubiquitous and distributed computing or embedded and hybrid systems. In modeling cyber-physical systems one has to consider the interaction between physics, computation and communication (networking), and a formal framework to studythis systems has to be invented. In this paper we develop a formal approach called Hilbertean formal methods to provide a denotational semantics for cyber-physical systems. We combine denotational semantics with an algebraic model for physical processes to model physical causality and observability.

A Formal Framework for User Centric Control of Probabilistic Multi-agent Cyber-Physical Systems

Abstract: Cyber physical systems are examples of a new emerging modelling paradigm that can be defined as multi-dimensional system co-engineering (MScE). In MScE, different aspects of complex systems are considered altogether, producing emergent properties, or loosing some useful ones. This holistic approach requires interdisciplinary methods that result from formal mathematical and AI co-engineering. In this paper, we propose a formal framework consisting of a reference model for multi-agent cyber physical systems, and a formal logic for expressing safety properties. The agents we consider are enabled with continuous physical mobility and evolve in an uncertain physical environment. Moreover, the model is user centric, by defining a complex control that considers the output of a runtime verification process, and possible commands of a human controller. The formal logic, called safety analysis logic (SafAL), combines probabilities with epistemic operators. In SafAL, one can specify the reachability properties of one agent, as well as prescriptive commands to the user. We define symmetry reduction semantics and a new concept of bisimulation for agents. A full abstraction theorem is presented, and it is proved that SafAL represents a logical characterization of bisimulation. A foundational study is carried out for model checking SafAL formulae against Markov models. A fundamental result states that the bisimulation preserves the probabilities of the reachable state sets.

Complexities of information security in Cyber-Physical Power Systems

Abstract: Cyber-Physical Power Systems consist of significant cyber components that mange the physical electric power infrastructure under distributed control of power electronics devices. This represents a departure from more centralized SCADA-type control. NERC Critical Infrastructure Protection standards emphasize the need to protect the power infrastructure from both cyber and physical attacks. Complex interactions between the cyber and physical worlds introduce new vulnerabilities that go beyond those found in the purely computer world. In this paper, some of these new vulnerabilities are described and a direction is suggested to determine and mitigate these vulnerabilities.