Showing papers on "Cyber-physical system published in 2011"

For the Grid and Through the Grid: The Role of Power Line Communications in the Smart Grid

Abstract: Are Power Line Communications (PLC) a good candidate for Smart Grid applications? The objective of this paper is to address this important question. To do so, we provide an overview of what PLC can deliver today by surveying its history and describing the most recent technological advances in the area. We then address Smart Grid applications as instances of sensor networking and network control problems and discuss the main conclusions one can draw from the literature on these subjects. The application scenario of PLC within the Smart Grid is then analyzed in detail. Because a necessary ingredient of network planning is modeling, we also discuss two aspects of engineering modeling that relate to our question. The first aspect is modeling the PLC channel through fading models. The second aspect we review is the Smart Grid control and traffic modeling problem which allows us to achieve a better understanding of the communications requirements. Finally, this paper reports recent studies on the electrical and topological properties of a sample power distribution network. Power grid topological studies are very important for PLC networking as the power grid is not only the information source but also the information delivery system-a unique feature when PLC is used for the Smart Grid.

Cyber-physical Systems

Abstract: Cyber-Physical Systems (CPS) allow the interaction between two worlds, machines and the internet, by means of a computer-based algorithm tightly coupled with the user. They are typically highly complex and distributed systems. Embedded systems collect and process data (e.g., sensor data) and control the CPS’s mechanic components. Cyber-Physical Systems can be used in a wide range of applications, e.g., aerospace, manufacturing, automotive, chemistry, medicine, entertainment, and energy systems.

Attacks against process control systems: risk assessment, detection, and response

Abstract: In the last years there has been an increasing interest in the security of process control and SCADA systems. Furthermore, recent computer attacks such as the Stuxnet worm, have shown there are parties with the motivation and resources to effectively attack control systems.While previous work has proposed new security mechanisms for control systems, few of them have explored new and fundamentally different research problems for securing control systems when compared to securing traditional information technology (IT) systems. In particular, the sophistication of new malware attacking control systems--malware including zero-days attacks, rootkits created for control systems, and software signed by trusted certificate authorities--has shown that it is very difficult to prevent and detect these attacks based solely on IT system information.In this paper we show how, by incorporating knowledge of the physical system under control, we are able to detect computer attacks that change the behavior of the targeted control system. By using knowledge of the physical system we are able to focus on the final objective of the attack, and not on the particular mechanisms of how vulnerabilities are exploited, and how the attack is hidden. We analyze the security and safety of our mechanisms by exploring the effects of stealthy attacks, and by ensuring that automatic attack-response mechanisms will not drive the system to an unsafe state.A secondary goal of this paper is to initiate the discussion between control and security practitioners--two areas that have had little interaction in the past. We believe that control engineers can leverage security engineering to design--based on a combination of their best practices--control algorithms that go beyond safety and fault tolerance, and include considerations to survive targeted attacks.

A survey of Cyber-Physical Systems

Abstract: Cyber-Physical Systems (CPSs) are characterized by integrating computation and physical processes. The theories and applications of CPSs face the enormous challenges. The aim of this work is to provide a better understanding of this emerging multi-disciplinary methodology. First, the features of CPSs are described, and the research progresses are summarized from different perspectives such as energy control, secure control, transmission and management, control technique, system resource allocation, and model-based software design. Then three classic applications are given to show that the prospects of CPSs are engaging. Finally, the research challenges and some suggestions for future work are in brief outlined.

TRM-IoT: A trust management model based on fuzzy reputation for internet of things

Abstract: Since a large scale Wireless Sensor Network (WSN) is to be completely integrated into Internet as a core part of Internet of Things (IoT) or Cyber Physical System (CPS), it is necessary to consider various security challenges that come with IoT/CPS, such as the detection of malicious attacks. Sensors or sensor embedded things may establish direct communication between each other using 6LoWPAN protocol. A trust and reputation model is recognized as an important approach to defend a large distributed sensor networks in IoT/CPS against malicious node attacks, since trust establishment mechanisms can stimulate collaboration among distributed computing and communication entities, facilitate the detection of untrustworthy entities, and assist decision-making process of various protocols. In this paper, based on in-depth understanding of trust establishment process and quantitative comparison among trust establishment methods, we present a trust and reputation model TRM-IoT to enforce the cooperation between things in a network of IoT/CPS based on their behaviors. The accuracy, robustness and lightness of the proposed model is validated through a wide set of simulations.

A Taxonomy of Cyber Attacks on SCADA Systems

Abstract: Supervisory Control and Data Acquisition(SCADA) systems are deeply ingrained in the fabric of critical infrastructure sectors. These computerized real-time process control systems, over geographically dispersed continuous distribution operations, are increasingly subject to serious damage and disruption by cyber means due to their standardization and connectivity to other networks. However, SCADA systems generally have little protection from the escalating cyber threats. In order to understand the potential danger and to protect SCADA systems, in this paper, we highlight their difference from standard IT systems and present a set of security property goals. Furthermore, we focus on systematically identifying and classifying likely cyber attacks including cyber-induced cyber-physical attack son SCADA systems. Determined by the impact on control performance of SCADA systems, the attack categorization criteria highlights commonalities and important features of such attacks that define unique challenges posed to securing SCADA systems versus traditional Information Technology(IT) systems.

Towards autonomous vehicular clouds

Abstract: The dawn of the 21st century has seen a growing interest in vehicular networking and its myriad potential applications. The initial view of practitioners and researchers was that radio-equipped vehicles could keep the drivers informed about potential safety risks and increase their awareness of road conditions. The view then expanded to include access to the Internet and associated services. This position paper proposes and promotes a novel and more comprehensive vision namely, that advances in vehicular networks, embedded devices, and cloud computing will enable the formation of autonomous clouds of vehicular computing, communication, sensing, power and physical resources. Hence, we coin the term, Autonomous Vehicular Clouds (AVCs). A key features distinguishing AVCs from conventional cloud computing is that mobile AVC resources can be pooled dynamically to serve authorized users and to enable autonomy in real-time service sharing and management on terrestrial, aerial, or aquatic pathways or theatres of operations. In addition to general-purpose AVCs, we also envision the emergence of specialized AVCs such as mobile analytics laboratories. Furthermore, we envision that the integration of AVCs with ubiquitous smart infrastructures including intelligent transportation systems, smart cities, and smart electric power grids, will have an enormous societal impact enabling ubiquitous utility cyber-physical services at the right place, right time, and with right-sized resources.

Petri Net Modeling of Cyber-Physical Attacks on Smart Grid

Abstract: This paper investigates the use of Petri nets for modeling coordinated cyber-physical attacks on the smart grid. Petri nets offer more flexibility and expressiveness than traditional attack trees to represent the actions of simultaneous attackers. However, Petri net models for attacks on very large critical infrastructures such as the smart grid require a great amount of manual effort and detailed expertise in cyber-physical threats. To overcome these obstacles, we propose a novel hierarchical method to construct large Petri nets from a number of smaller Petri nets that can be created separately by different domain experts. The construction method is facilitated by a model description language that enables identical places in different Petri nets to be matched. The new modeling approach is described for an example attack on smart meters, and its efficacy is demonstrated by a proof-of-concept Python program.

A model-based design methodology for cyber-physical systems

Abstract: Model-based design is a powerful design technique for cyber-physical systems, but too often literature assumes knowledge of a methodology without reference to an explicit design process, instead focusing on isolated steps such as simulation, software synthesis, or verification. We combine these steps into an explicit and holistic methodology for model-based design of cyber-physical systems from abstraction to architecture, and from concept to realization. We decompose model-based design into ten fundamental steps, describe and evaluate an iterative design methodology, and evaluate this methodology in the development of a cyber-physical system.

Cyber-physical attacks in power networks: Models, fundamental limitations and monitor design

Abstract: Future power networks will be characterized by safe and reliable functionality against physical and cyber attacks. This paper proposes a unified framework and advanced monitoring procedures to detect and identify network components malfunction or measurements corruption caused by an omniscient adversary. We model a power system under cyber-physical attack as a linear time-invariant descriptor system with unknown inputs. Our attack model generalizes the prototypical stealth, (dynamic) false-data injection and replay attacks. We characterize the fundamental limitations of both static and dynamic procedures for attack detection and identification. Additionally, we design provably-correct (dynamic) detection and identification procedures based on tools from geometric control theory. Finally, we illustrate the effectiveness of our method through a comparison with existing (static) detection algorithms, and through a numerical study.

Robust and resilient control design for cyber-physical systems with an application to power systems

Abstract: The tradeoff between robustness and resilience is a pivotal design issue for modern industrial control systems. The trend of integrating information technologies into control system infrastructure has made resilience an important dimension of the critical infrastructure protection mission. It is desirable that systems support state awareness of threats and anomalies, and maintain acceptable levels of operation or service in the face of unanticipated or unprecedented incidents. In this paper, we propose a hybrid theoretical framework for robust and resilient control design in which the stochastic switching between structure states models unanticipated events and deterministic uncertainties in each structure represent the known range of disturbances. We propose a set of coupled optimality criteria for a holistic robust and resilient design for cyber-physical systems. We apply this method to a voltage regulator design problem for a synchronous machine with infinite bus and illustrate the solution methodology with numerical examples.

Advances in Cyber-Physical Systems Research

Abstract: Cyber-physical systems (CPSs) are an emerging discipline that involves engineered computing and communicating systems interfacing the physical world. The widespread applications of CPSs still face enormous challenges because of the lack of theoretical foundations. In this technical survey, we review state-of-the-art design techniques from various angles. The aim of this work is to provide a better understanding of this emerging multidisciplinary methodology. The features of CPSs are described, and the research progress is analyzed using the following aspects: energy management, network security, data transmission and management, model-based design, control technique, and system resource allocation. We focus on CPS resource optimization, and propose a system performance optimization model with resource constraints. In addition, some classic applications (e.g., integrating intelligent road with unmanned vehicle) are provided to show that the prospects of CPSs are promising. Furthermore, research challenges and suggestions for future work are outlined in brief.

Cyber-Physical Systems in the SmartGrid

Abstract: Radical changes are expected to occur in the next years in the electricity domain and the grid itself which has been almost unchanged the last 100 years. Value is created when interactions exist and this is the main thrust of the emerging SmartGrid which will heavily rely on IT technologies at several layers for monitoring and control. The basic building blocks are the existing efforts in the domain of the Internet of Things and Internet of Services, that come together with cooperation as the key enabler. The SmartGrid is a complex ecosystem of heterogeneous (cooperating) entities that interact in order to provide the envisioned functionality. Advanced business services will take advantage of the near real-time information flows among all participants. In order to realize the SmartGrid promise we will have to heavily depend on Cyber-Physical Systems (CPS) that will be able to monitor, share and manage information and actions on the business as well as the real world. CPS is seen as an integral part of the SmartGrid, hence several open issues will need to be effectively addressed.

Cyber-Physical-Social Systems for Command and Control

Abstract: The article provides a preliminary account of the operational process of command and control based on the cyber-physical-social system (CPSS) and a self-synchronization mechanism. The proposed CPSS for command and control incorporates the essential characteristics of operational mechanism and connects the physical network, cyberspace, mental space, and social network.

V-Cloud: vehicular cyber-physical systems and cloud computing

Abstract: The widespread use of smart phone devices and their ubiquity has brought up new application domains. One such interesting domain is vehicular networks. Furthermore, cloud computing is a next-generation information and communication technology that is gaining popularity due to its pay-as-you-go service model. In this paper, we propose our novel V-Cloud architecture which includes vehicular cyber-physical system (VCPS), vehicle-to-vehicle network (V2V) and vehicle-to-infrastructure network (V2I) layers. Each of these layers is explained in further details. We discuss research challenges in V-Cloud domain and introduce new services to show wide potential of such intelligent transportation system to meet safety and comfort requirements for driver.

Real-Time Modeling for Direct Load Control in Cyber-Physical Power Systems

Abstract: This paper presents an innovative approach to use real-time scheduling techniques for the automation of electric loads in Cyber-Physical Power Systems. The goal is to balance the electric power usage to achieve an optimized upper bound on the power peak load, while guaranteeing specific constraints on the physical process controlled by the electric loads. Timing parameters derived from the scheduling discipline of real-time computing systems are used to model electric devices. Real-time scheduling algorithms can be exploited to achieve the upper bound by predictably and timely switching on/off the devices composing the electrical system. The paper shows the relevance of electric load balancing in power systems to motivate the use of real-time techniques to achieve predictability of electric loads scheduling. Real-Time Physical Systems (RTPS) are introduced as a novel modeling methodology of a physical system based on real-time parameters. They enable the use of traditional real-time system models and scheduling algorithms, with adequate adaptations, to manage loads activation/deactivation. The model of the physical process considered in this work is characterized by uncertainties that are compensated by a suitable feedback control policy, based on the dynamic adaptation of real-time parameter values. A number of relevant relationships between real-time and physical parameters are derived.

Modeling Analysis and Control Research Framework of Cyber Physical Power Systems

Abstract: To implement the objective of smart grids,it is essential to introduce the state-of-the-art computing,communication and sensing technologies.Traditionally,the theoretical foundation and methodologies of power systems and information systems are independent.Thus,the existing power system analysis and control methods cannot adequately take into account the impacts of the information system.The cyber physical system(CPS) represents a new research area with a focus on integrating physical and information systems so as to build a new and powerful industrial system.Based on CPS and the characteristics of power systems,the concept of a cyber physical power system(CPPS) framework is presented.Several mathematical tools including the differential and algebraic equation set,finite automation,stochastic process and queueing theory are introduced to formulate the steady-state and dynamic models of CPPS.The steady-state and dynamic analysis of information systems is then introduced,and on this basis,the research direction for reliability and security of CPPS is developed.The networked control of CPPS is finally discussed,and new methods based on the delay and data loss compensation are proposed.

Stackelberg-game analysis of correlated attacks in cyber-physical systems

Abstract: This paper studies a resilient control problem for discrete-time, linear time-invariant systems subject to state and input constraints. State measurements and control laws are transmitted over a communication network and could be corrupted by human adversaries. In particular, we consider a class of human adversaries, namely correlated jammers, who are modeled as rational decision makers and whose strategies are highly correlated to the control system operator. The coupled decision making process is modeled as a two-level receding-horizon dynamic Stackelberg (leader-follower) game. We propose a receding-horizon Stackelberg control law for the operator, and analyze the resulting performance and closed-loop stability of the system under correlated attacks. We observe that, with full information of his follower, the operator is still able to maintain regional stability of the control system.

View Consistency in Architectures for Cyber-Physical Systems

Abstract: Current methods for modeling, analysis, and design of cyber-physical systems lack a unifying framework due to the complexity and heterogeneity of the constituent elements and their interactions. Our approach is to define relationships between system models at the architectural level, which captures the structural interdependencies and some semantic interdependencies between representations without attempting to comprehend all of the details of any particular modeling formalism. This paper addresses the issue of defining and evaluating consistency between architectural views imposed by various heterogeneous models and a base architecture (BA) for the complete system. This notion of structural consistency ensures that the model elements adhere to the cyber and physical types and the connections between components present in the BA, which serves as the unifying framework for model-based development. Consistency checking between a model and the underlying system architecture is formulated as a typed graph matching problem between the connectivity graphs of the corresponding architectural view and the system's BA. The usefulness of the approach to check system modeling assumptions is illustrated in the context of two heterogeneous views of a quad rotor air vehicle.

Web-of-things framework for cyber–physical systems

Abstract: The recent development of Web-of-Things (WoT) and Cyber–Physical Systems (CPS) raises a new requirement of connecting abstract computational artifacts with the physical world. This requires both new theories and engineering practices that model cyber and physical resources in a unified framework, a challenge that few current approaches are able to tackle. The solution must break the boundary between the cyber world and the physical world by providing a unified infrastructure that permits integrated models addressing issues from both worlds simultaneously. This paper proposes a framework to integrate WoT and CPS. A case study is presented to demonstrate the advantage of the framework. Copyright © 2010 John Wiley & Sons, Ltd.

Synthesis of Static Communication Schedules for Mixed-Criticality Systems

Abstract: Throughout many application areas of embedded and cyber-physical systems there is a demand to integrate more and more applications such that they share common resources. These applications may have different levels of criticality with respect to temporal or fault-tolerance properties and we call the result of their integration a mixed-criticality system. The communication network is a resource of particular importance and nowadays the system architecture is highly determined by a network's capabilities. A network for mixed-criticality systems has to establish partitioning such that the influence of messages from different applications on each other is bounded and the impact of low-critical messages on high-critical ones is minimized or removed at all. A straight forward way to establish network-wide partitioning is the time-triggered communication paradigm in which the communication schedule on the network is defined at design time and executed with respect to a globally synchronized time base. In this paper we discuss static scheduling methods for time-triggered traffic such that it can co-exist with non-time-triggered traffic. We introduce the concept of "schedule porosity'' and show the impact of time-triggered traffic on unsynchronized traffic as a function of schedule porosity.

Sandboxing Controllers for Cyber-Physical Systems

Abstract: Cyber-physical systems bridge the gap between cyber components, typically written in software, and the physical world. Software written with traditional development practices, however, likely contains bugs or unintended interactions among components, which can result in uncontrolled and possibly disastrous physical-world interactions. Complete verification of cyber-physical systems, however, is often impractical due to outsourced development of software, cost, software created without formal models, or excessively large or complex models where the verification process becomes intractable. Rather than mandating complete modeling and verification, we advocate sandboxing of unverified cyber-physical system controllers by augmenting the system with a verified safety wrapper that can take control of the plant in order to avoid violations of formal safety properties. The focus of this work is an automatic method, based on reach ability and time-bounded reach ability of hybrid systems, to generate verified sandboxes. The method is shown to be both more general than previous work, and allows the trade-off of increased computation time for improved reach ability accuracy. We also present an end-to-end toolkit which performs the low-level computation to generate the sandbox source code from Simulink/State flow models of a cyber-physical system.

Evaluating IEEE 802.15.4 for Cyber-Physical Systems

Abstract: With rapid advancements in sensing, networking, and computing technologies, recent years have witnessed the emergence of cyber-physical systems (CPS) in a broad range of application domains. CPS is a new class of engineered systems that features the integration of computation, communications, and control. In contrast to general-purpose computing systems, many cyber-physical applications are safety critical. These applications impose considerable requirements on quality of service (QoS) of the employed networking infrastruture. Since IEEE 802.15.4 has been widely considered as a suitable protocol for CPS over wireless sensor and actuator networks, it is of vital importance to evaluate its performance extensively. Serving for this purpose, this paper will analyze the performance of IEEE 802.15.4 standard operating in different modes respectively. Extensive simulations have been conducted to examine how network QoS will be impacted by some critical parameters. The results are presented and analyzed, which provide some useful insights for network parameter configuration and optimization for CPS design.

A survey on Cyber Physical Energy Systems and their applications on smart grids

Abstract: An important challenge for future energy systems is a new modeling methodology that integrates the cyber and physical components. This model must include the impact of communication networks and further cyber components, besides the relevant information of the physical system, in terms of efficiency, sustainability, reliability, security, and stability. The Cyber Physical Energy Systems (CPES) concept is presented as an interesting alternative to address this issue and its main features are identified. The main CPES research areas are identified as: modelling energy systems, energy efficiency, energy resource management, and energy control. In this work, the advantages of the CPES approach are shown in order to address current challenges in future energy systems. Smart grids, based on microgrids and distributed generation concepts, are identified as an interesting application of the CPES. A new proposal for modeling smart grids based on the CPES approach is introduced.

A Secured Health Care Application Architecture for Cyber-Physical Systems

Abstract: Cyber-physical systems (CPS) can be viewed as a new generation of systems with integrated control, communication and computational capabilities. Like the internet transformed how humans interact with one another, cyber-physical systems will transform how people interact with the physical world. Currently, the study of CPS is still in its infancy and there exist many research issues and challenges ranging from electricity power, health care, transportation and smart building etc. In this paper, an introduction of CPeSC 3 (cyber physical enhanced secured wireless sensor networks integrated cloud computing for u-life care) architecture and its application to the health care monitoring and decision support systems is given. The proposed CPeSC 3 architecture is composed of three main components, namely 1) communication core, 2) computation core, and 3) resource scheduling and management core. Detailed analysis and explanations are given for relevant models such as cloud computing, real time scheduling and security models. Finally, a medical health care application scenario is presented based on our practical test-bed which has been built for 3 years.

Addressing Modeling Challenges in Cyber-Physical Systems

Abstract: : This paper focuses on the challenges of modeling cyber-physical systems that arise from the intrinsic heterogeneity, concurrency, and sensitivity to timing of such systems. It uses a portion of an aircraft vehicle management systems (VMS), specifically the fuel management subsystem, to illustrate the challenges and then discusses technologies that at least partially address the challenges. Specific technologies described include hybrid system modeling and simulation, concurrent and heterogeneous models of computation, the use of domain-specific ontologies to enhance modularity, and the joint modeling of functionality and implementation architectures.

Co-design of cyber-physical systems via controllers with flexible delay constraints

Abstract: In this paper, we consider a cyber-physical architecture where control applications are divided into multiple tasks, spatially distributed over various processing units that communicate via a shared bus. While control signals are exchanged over the communication bus, they have to wait for bus access and therefore experience a delay. We propose certain (co-)design guidelines for (i) the communication schedule, and (ii) the controller, such that stability of the control applications is guaranteed for more flexible communication delay constraints than what has been studied before. We illustrate the applicability of our design approach using the FlexRay dynamic segment as the communication medium for the processing units.