Showing papers on "Cyber-physical system published in 2012"

Attack Detection and Identification in Cyber-Physical Systems -- Part I: Models and Fundamental Limitations

Abstract: Cyber-physical systems integrate computation, communication, and physical capabilities to interact with the physical world and humans. Besides failures of components, cyber-physical systems are prone to malignant attacks, and specific analysis tools as well as monitoring mechanisms need to be developed to enforce system security and reliability. This paper proposes a unified framework to analyze the resilience of cyber-physical systems against attacks cast by an omniscient adversary. We model cyber-physical systems as linear descriptor systems, and attacks as exogenous unknown inputs. Despite its simplicity, our model captures various real-world cyber-physical systems, and it includes and generalizes many prototypical attacks, including stealth, (dynamic) false-data injection and replay attacks. First, we characterize fundamental limitations of static, dynamic, and active monitors for attack detection and identification. Second, we provide constructive algebraic conditions to cast undetectable and unidentifiable attacks. Third, by using the system interconnection structure, we describe graph-theoretic conditions for the existence of undetectable and unidentifiable attacks. Finally, we validate our findings through some illustrative examples with different cyber-physical systems, such as a municipal water supply network and two electrical power grids.

Cyber–Physical Security of a Smart Grid Infrastructure

Abstract: It is often appealing to assume that existing solutions can be directly applied to emerging engineering domains. Unfortunately, careful investigation of the unique challenges presented by new domains exposes its idiosyncrasies, thus often requiring new approaches and solutions. In this paper, we argue that the “smart” grid, replacing its incredibly successful and reliable predecessor, poses a series of new security challenges, among others, that require novel approaches to the field of cyber security. We will call this new field cyber-physical security. The tight coupling between information and communication technologies and physical systems introduces new security concerns, requiring a rethinking of the commonly used objectives and methods. Existing security approaches are either inapplicable, not viable, insufficiently scalable, incompatible, or simply inadequate to address the challenges posed by highly complex environments such as the smart grid. A concerted effort by the entire industry, the research community, and the policy makers is required to achieve the vision of a secure smart grid infrastructure.

Cyber-Physical Security of a Smart Grid Infrastructure The authors of this paper discuss the limitations of advances, measures to make the smart grid secure, and also to assure continuous power flows and dynamic power pricing.

Abstract: It is often appealing to assume that existing solutions can be directly applied to emerging engineering do- mains. Unfortunately, careful investigation of the unique chal- lenges presented by new domains exposes its idiosyncrasies, thus often requiring new approaches and solutions. In this paper, we argue that the Bsmart( grid, replacing its incredibly successful and reliable predecessor, poses a series of new se- curity challenges, among others, that require novel approaches to the field of cyber security. We will call this new field cyber- physical security. The tight coupling between information and communication technologies and physical systems introduces new security concerns, requiring a rethinking of the commonly used objectives and methods. Existing security approaches are either inapplicable, not viable, insufficiently scalable, incom- patible, or simply inadequate to address the challenges posed by highly complex environments such as the smart grid. A con- certed effort by the entire industry, the research community, and the policy makers is required to achieve the vision of a secure smart grid infrastructure.

Cyber–Physical Systems: A Perspective at the Centennial

Abstract: Cyber-physical systems (CPSs) are the next generation of engineered systems in which computing, communication, and control technologies are tightly integrated. Research on CPSs is fundamentally important for engineered systems in many important application domains such as transportation, energy, and medical systems. We overview CPS research from both a historical point of view in terms of technologies developed for early generations of control systems, as well as recent results on CPSs in many relevant research domains such as networked control, hybrid systems, real-time computing, real-time networking, wireless sensor networks, security, and model-driven development. We outline the potential for CPSs in many societally important application domains.

Modeling Cyber–Physical Systems

Abstract: This paper focuses on the challenges of modeling cyber-physical systems (CPSs) that arise from the intrinsic heterogeneity, concurrency, and sensitivity to timing of such systems. It uses a portion of an aircraft vehicle management system (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.

Challenges and Research Directions in Medical Cyber–Physical Systems

Abstract: Medical cyber-physical systems (MCPS) are life-critical, context-aware, networked systems of medical devices. These systems are increasingly used in hospitals to provide high-quality continuous care for patients. The need to design complex MCPS that are both safe and effective has presented numerous challenges, including achieving high assurance in system software, intoperability, context-aware intelligence, autonomy, security and privacy, and device certifiability. In this paper, we discuss these challenges in developing MCPS, some of our work in addressing them, and several open research issues.

Toward a Science of Cyber–Physical System Integration

Abstract: System integration is the elephant in the china store of large-scale cyber-physical system (CPS) design. It would be hard to find any other technology that is more undervalued scientifically and at the same time has bigger impact on the presence and future of engineered systems. The unique challenges in CPS integration emerge from the heterogeneity of components and interactions. This heterogeneity drives the need for modeling and analyzing cross-domain interactions among physical and computational/networking domains and demands deep understanding of the effects of heterogeneous abstraction layers in the design flow. To address the challenges of CPS integration, significant progress needs to be made toward a new science and technology foundation that is model based, precise, and predictable. This paper presents a theory of composition for heterogeneous systems focusing on stability. Specifically, the paper presents a passivity-based design approach that decouples stability from timing uncertainties caused by networking and computation. In addition, the paper describes cross-domain abstractions that provide effective solution for model-based fully automated software synthesis and high-fidelity performance analysis. The design objectives demonstrated using the techniques presented in the paper are group coordination for networked unmanned air vehicles (UAVs) and high-confidence embedded control software design for a quadrotor UAV. Open problems in the area are also discussed, including the extension of the theory of compositional design to guarantee properties beyond stability, such as safety and performance.

Machine-to-Machine Communications: Architectures, Standards and Applications

Abstract: As a new business concept, machine-to-machine (M2M) communications are born from original telemetry technology with the intrinsic features of automatic data transmissions and measurement from remote sources typically by cable or radio. M2M includes a number of technologies that need to be combined in a compatible manner to enable its deployment over a broad market of consumer electronics. In order to provide better understanding for this emerging concept, the correlations among M2M, wireless sensor networks, cyber-physical systems (CPS), and internet of things are first analyzed in this paper. Then, the basic M2M architecture is introduced and the key elements of the architecture are presented. Furthermore, the progress of global M2M standardization is reviewed, and some representative applications (i.e., smart home, smart grid and health care) are given to show that the M2M technologies are gradually utilized to benefit people’s life. Finally, a novel M2M system integrating intelligent road with unmanned vehicle is proposed in the form of CPS, and an example of cyber-transportation systems for improving road safety and efficiency are introduced.

Ensuring Safety, Security, and Sustainability of Mission-Critical Cyber–Physical Systems

Abstract: Cyber-physical systems (CPSs) couple their cyber and physical parts to provide mission-critical services, including automated pervasive health care, smart electricity grid, green cloud computing, and surveillance with unmanned aerial vehicles (UAVs). CPSs can use the information available from the physical environment to provide such ubiquitous, energy-efficient and low-cost functionalities. Their operation needs to ensure three key properties, collectively referred to as S3: 1) safety: avoidance of hazards; 2) security: assurance of integrity, authenticity, and confidentiality of information; and 3) sustainability: maintenance of long-term operation of CPSs using green sources of energy. Ensuring S3 properties in a CPS is a challenging task given the spatio-temporal dynamics of the underlying physical environment. In this paper, the formal underpinnings of recent CPS S3 solutions are aligned together in a theoretical framework for cyber-physical interactions, empowering CPS researchers to systematically design solutions for ensuring safety, security, or sustainability. The general applicability of this framework is demonstrated with various exemplar solutions for S3 in diverse CPS domains. Further, insights are provided on some of the open research problems for ensuring S3 in CPSs.

Attack Detection and Identification in Cyber-Physical Systems -- Part II: Centralized and Distributed Monitor Design

Abstract: Cyber-physical systems integrate computation, communication, and physical capabilities to interact with the physical world and humans. Besides failures of components, cyber-physical systems are prone to malicious attacks so that specific analysis tools and monitoring mechanisms need to be developed to enforce system security and reliability. This paper builds upon the results presented in our companion paper [1] and proposes centralized and distributed monitors for attack detection and identification. First, we design optimal centralized attack detection and identification monitors. Optimality refers to the ability of detecting (respectively identifying) every detectable (respectively identifiable) attack. Second, we design an optimal distributed attack detection filter based upon a waveform relaxation technique. Third, we show that the attack identification problem is computationally hard, and we design a sub-optimal distributed attack identification procedure with performance guarantees. Finally, we illustrate the robustness of our monitors to system noise and unmodeled dynamics through a simulation study.

Challenges and Research Directions in Medical Cyber-Physical Systems A broad overview of emerging applications for these systems is provided in this paper; challenges, promising solutions, and open problems are presented.

Abstract: Medical cyber-physical systems (MCPS) are life- critical, context-aware, networked systems of medical devices. These systems are increasingly used in hospitals to provide high-quality continuous care for patients. The need to design complex MCPS that are both safe and effective has presented numerous challenges, including achieving high assurance in system software, intoperability, context-aware intelligence, autonomy, security and privacy, and device certifiability. In this paper, we discuss these challenges in developing MCPS, some of our work in addressing them, and several open research issues.

Optimal Allocation of Interconnecting Links in Cyber-Physical Systems: Interdependence, Cascading Failures, and Robustness

Abstract: We consider a cyber-physical system consisting of two interacting networks, i.e., a cyber network overlaying a physical network. It is envisioned that these systems are more vulnerable to attacks since node failures in one network may result in (due to the interdependence) failures in the other network, causing a cascade of failures that would potentially lead to the collapse of the entire infrastructure. The robustness of interdependent systems against this sort of catastrophic failure hinges heavily on the allocation of the (interconnecting) links that connect nodes in one network to nodes in the other network. In this paper, we characterize the optimum inter-link allocation strategy against random attacks in the case where the topology of each individual network is unknown. In particular, we analyze the “regular” allocation strategy that allots exactly the same number of bidirectional internetwork links to all nodes in the system. We show, both analytically and experimentally, that this strategy yields better performance (from a network resilience perspective) compared to all possible strategies, including strategies using random allocation, unidirectional interlinks, etc.

A Cyber–Physical Systems Approach to Data Center Modeling and Control for Energy Efficiency

Abstract: This paper presents data centers from a cyber-physical system (CPS) perspective. Current methods for controlling information technology (IT) and cooling technology (CT) in data centers are classified according to the degree to which they take into account both cyber and physical considerations. To evaluate the potential impact of coordinated CPS strategies at the data center level, we introduce a control-oriented model that represents the data center as two coupled networks: a computational network representing the cyber dynamics and a thermal network representing the physical dynamics. These networks are coupled through the influence of the IT on both networks: servers affect both the quality of service (QoS) delivered by the computational network and the generation of heat in the thermal network. Using this model, three control strategies are evaluated with respect to their energy efficiency and computational performance: a baseline strategy that ignores CPS considerations, an uncoordinated strategy that manages the IT and CT independently, and a coordinated strategy that manages the IT and CT together to achieve optimal performance with respect to both QoS and energy efficiency. Simulation results show that the benefits to be realized from coordinating the control of IT and CT depend on the distribution and heterogeneity of the computational and cooling resources throughout the data center. A new cyber-physical index (CPI) is introduced as a measure of this combined distribution of cyber and physical effects in a given data center. We illustrate how the CPI indicates the potential impact of using coordinated CPS control strategies.

SCPSE: Security-Oriented Cyber-Physical State Estimation for Power Grid Critical Infrastructures

Abstract: Preserving the availability and integrity of the power grid critical infrastructures in the face of fast-spreading intrusions requires advances in detection techniques specialized for such large-scale cyber-physical systems. In this paper, we present a security-oriented cyber-physical state estimation (SCPSE) system, which, at each time instant, identifies the compromised set of hosts in the cyber network and the maliciously modified set of measurements obtained from power system sensors. SCPSE fuses uncertain information from different types of distributed sensors, such as power system meters and cyber-side intrusion detectors, to detect the malicious activities within the cyber-physical system. We implemented a working prototype of SCPSE and evaluated it using the IEEE 24-bus benchmark system. The experimental results show that SCPSE significantly improves on the scalability of traditional intrusion detection techniques by using information from both cyber and power sensors. Furthermore, SCPSE was able to detect all the attacks against the control network in our experiments.

Multicast Routing for Decentralized Control of Cyber Physical Systems with an Application in Smart Grid

Abstract: In cyber physical systems, communication is needed for conveying sensor observations to controllers; thus, the design of the communication sub-system is of key importance for the stabilization of system dynamics In this paper, multicast routing is studied for networking of decentralized sensors and controllers The challenges of uncertain destinations and multiple routing modes, which are significantly different from traditional data networks, are addressed by employing the theories of hybrid systems and linear matrix inequalities, thus forming a novel framework for studying the communication sub-system in cyber physical systems Both cases of neglible delay and non-negligible delay are discussed The proposed framework is then applied in the context of voltage control in smart grid Numerical simulations using a 4-bus power grid model show that the proposed framework and algorithm can effectively stabilize cyber physical systems

Distributed Real-Time Software for Cyber–Physical Systems

Abstract: Real-time embedded software today is commonly built using programming abstractions with little or no temporal semantics. This paper addresses this problem by presenting a programming model called programming temporally integrated distributed embedded systems (PTIDES) that serves as a coordination language for model-based design of distributed real-time embedded systems. Specifically, the paper describes the principles of PTIDES, which leverages network time synchronization to provide a determinate distributed real-time semantics. We show how PTIDES can function as a coordination language, orchestrating components that may be designed and specified using different formalisms. We show the use of this environment in the design of interesting and practical cyber-physical systems, such as a power plant control system.

Alleviating Solar Energy Congestion in the Distribution Grid via Smart Metering Communications

Abstract: The operation and control of the existing power grid system, which is challenged with rising demands and peak loads, has been considered passive. Congestion is often discovered in high-demand regions, and at locations where abundant renewable energy is generated and injected into the grid; this is attributed to a lack of transmission lines, transfer capability, and transmission capacity. While developing distributed generation (DG) tends to alleviate the traditional congestion problem, employing information and communications technology (ICT) helps manage DG more effectively. ICT involves a vast amount of data to facilitate a broader knowledge of the network status. Data computation and communications are critical elements that can impact the system performance. In this paper, we consider congestion caused by power surpluses produced from households' solar units on rooftops or on ground. Disconnecting some solar units is required to maintain the reliability of the distribution grid. We propose a model for the disconnection process via smart metering communications between smart meters and the utility control center. By modeling the surplus congestion issue as a knapsack problem, we can solve it by proposed greedy solutions. Reduced computation time and data traffic in the network can be achieved.

Large scale simulation for human evacuation and rescue

Abstract: This paper surveys recent research on the use of sensor networks, communications and computer systems to enhance the human outcome of emergency situations. Areas covered include sensing, communication with evacuees and emergency personnel, path finding algorithms for safe evacuation, simulation and prediction, and decision tools. The systems being considered are a special instance of real-time cyber-physical-human systems that have become a crucial component of all large scale physical infrastructures such as buildings, campuses, sports and entertainment venues, and transportation hubs.

Cyber-Physical-Social Based Security Architecture for Future Internet of Things

Abstract: As the Internet of Things (IoT) is emerging as an attractive paradigm, a typical IoT architecture that U2IoT (Unit IoT and Ubiquitous IoT) model has been presented for the future IoT. Based on the U2IoT model, this paper proposes a cyber-physical-social based security architecture (IPM) to deal with Information, Physical, and Management security perspectives, and presents how the architectural abstractions support U2IoT model. In particular, 1) an information security model is established to describe the mapping relations among U2IoT, security layer, and security requirement, in which social layer and additional intelligence and compatibility properties are infused into IPM; 2) physical security referring to the external context and inherent infrastructure are inspired by artificial immune algorithms; 3) recommended security strategies are suggested for social management control. The proposed IPM combining the cyber world, physical world and human social provides constructive proposal towards the future IoT security and privacy protection.

RDDS: A Real-Time Data Distribution Service for Cyber-Physical Systems

Abstract: One of the primary requirements in many cyber-physical systems (CPS) is that the sensor data derived from the physical world should be disseminated in a timely and reliable manner to all interested collaborative entities. However, providing reliable and timely data dissemination services is especially challenging for CPS since they often operate in highly unpredictable environments. Existing network middleware has limitations in providing such services. In this paper, we present a novel publish/subscribe-based middleware architecture called Real-time Data Distribution Service (RDDS). In particular, we focus on two mechanisms of RDDS that enable timely and reliable sensor data dissemination under highly unpredictable CPS environments. First, we discuss the semantics-aware communication mechanism of RDDS that not only reduces the computation and communication overhead, but also enables the subscribers to access data in a timely and reliable manner when the network is slow or unstable. Further, we extend the semantics-aware communication mechanism to achieve robustness against unpredictable workloads by integrating a control-theoretic feedback controller at the publishers and a queueing-theoretic predictor at the subscribers. This integrated control loop provides Quality-of-Service (QoS) guarantees by dynamically adjusting the accuracy of the sensor models. We demonstrate the viability of the proposed approach by implementing a prototype of RDDS. The evaluation results show that, compared to baseline approaches, RDDS achieves highly efficient and reliable sensor data dissemination as well as robustness against unpredictable workloads.

Robust Control for Mobility and Wireless Communication in Cyber–Physical Systems With Application to Robot Teams

Abstract: In this paper, a system architecture to provide end-to-end network connectivity for autonomous teams of robots is discussed. The core of the proposed system is a cyber-physical controller whose goal is to ensure network connectivity as robots move to accomplish their assigned tasks. Due to channel quality uncertainties inherent to wireless propagation, we adopt a stochastic model where achievable rates are modeled as random variables. The cyber component of the controller determines routing variables that maximize the probability of having a connected network for given positions. The physical component determines feasible robot trajectories that are restricted to safe configurations which ensure these probabilities stay above a minimum reliability level. Local trajectory planning algorithms are proposed for simple environments and leveraged to obtain global planning algorithms to handle complex surroundings. The resulting integrated controllers are robust in that end-to-end communication survives with high probability even if individual point-to-point links are likely to fail with significant probability. Experiments demonstrate that the global planning algorithm succeeds in navigating a complex environment while ensuring that end-to-end communication rates meet or exceed prescribed values within a target failure tolerance.

On False Data Injection Attacks against Distributed Energy Routing in Smart Grid

Abstract: Smart Grid is a new type of energy-based cyber physical system (CPS) that will provide reliable, secure, and efficient energy transmission and distribution. The way to secure the distributed energy routing process that efficiently utilizes the distributed energy resources and minimizes the energy transmission overhead is essential in smart grid. In this paper, we study the vulnerability of the distributed energy routing process and investigate novel false data injection attacks against the energy routing process. We consider several general attacks, in which the adversary may manipulate the quantity of energy supply, the quantity of energy response, and the link state of energy transmission. The forged data injected by those attacks will cause imbalanced demand and supply, increase the cost for energy distribution, and disrupt the energy distribution. We formally model these attacks and quantitatively analyze their impact on energy distribution. Our evaluation data show that those attacks can effectively disrupt the effectiveness of energy distribution process, causing significant supplied energy loss, energy transmission cost and the number of outage users.

Cyber-Physical Systems - Concept, Challenges and Research Areas

Abstract: Cyber-Physical Systems (CPSs) represent an emerging research area that has attracted the attention of many researchers. Starting from the definition of CPS, the paper discusses the need for these systems implementation in various application domains and the research challenges for defining an appropriate formalism that represent more than networking and information technology - the information and knowledge will be integrated into physical objects. As CPSs are expected to play a major role in the design and development of future engineering systems, a short state of the art regarding the main CPS research areas (generic architecture, design principles, modeling, dependability, and implementation) ends the paper.

Cyber-physical systems: imminent challenges

Abstract: A German project is presented which was initiated in order to analyse the potential and risks associated with Cyber-Physical Systems. These have been recognised as the next wave of innovation in information and communication technology. Cyber-Physical Systems are herein understood in a very broad sense as the integration of embedded systems with global networks such as the Internet. The survey aims at deepening understanding the impact of those systems at technological and economical level as well as at political and sociological level. The goal of the study is to collect arguments for decision makers both in business and politics to take actions in research, legislation and business development.

Robust Control for Mobility and Wireless Communication in Cyber-Physical Systems With Application to Robot Teams Controlofanautonomousrobotteamwiththeaimofoptimizingnetworkperformance is discussed in this paper; the authors design a controller to ensure availability of communication resources.

Abstract: In this paper, a system architecture to provide end-to-end network connectivity for autonomous teams of robots is discussed. The core of the proposed system is a cyber- physical controller whose goal is to ensure network connec- tivity as robots move to accomplish their assigned tasks. Due to channel quality uncertainties inherent to wireless propagation, we adopt a stochastic model where achievable rates are modeled as random variables. The cyber component of the controller determines routing variables that maximize the probability of having a connected network for given positions. The physical component determines feasible robot trajectories that are restricted to safe configurations which ensure these probabilities stay above a minimum reliability level. Local trajectory planning algorithms are proposed for simple envir- onments and leveraged to obtain global planning algorithms to handle complex surroundings. The resulting integrated con- trollers are robust in that end-to-end communication survives with high probability even if individual point-to-point links are likely to fail with significant probability. Experiments demon- strate that the global planning algorithm succeeds in navigating a complex environment while ensuring that end-to-end com- munication rates meet or exceed prescribed values within a target failure tolerance.

The knowledge grid : toward cyber-physical society

Abstract: The Knowledge Grid is an intelligent and sustainable interconnection environment that consists of autonomous individuals, self-organized semantic communities, adaptive networking mechanisms, evolving semantic link networks keeping meaningful connection between individuals, flows for dynamic resource sharing, and mechanisms supporting effective resource management and providing appropriate knowledge services for learning, innovation, teamwork, problem solving, and decision making. This book presents its methodology, theory, models and applications systematically for the first time. Its second edition fulfills the ideal of the Knowledge Grid by increasing many up-to-date new contents, including: the systematic method of semantic link network that supports uncertainty management, discovery of semantic links and semantic communities, and autonomous semantic data model; semantic peer-to-peer infrastructures for efficient knowledge sharing; and, a new centrality measure of network and its application in e-science. This new edition will undoubtedly provide refreshing materials for researchers, academics, practitioners and students.

Viewpoints, formalisms, languages, and tools for cyber-physical systems

Abstract: Cyber-physical systems (CPS) are becoming indispensable in our modern way of life. As an application domain CPS is not new. As an intellectual discipline, however, it is. This paper focuses on CPS modeling, which is an essential activity in CPS design, with multiple challenges. In particular, stakeholders lack a systematic framework and guidelines to help them choose among the many available modeling languages and tools. We propose such a framework in this paper. Our framework consists of three elements: viewpoints, which capture the stakeholders' interests and concerns; concrete languages and tools, among which the stakeholders must make a selection when defining their CPS design environments; and abstract, mathematical formalisms, which are the "semantic glue" linking the two worlds. As part of the framework, we survey various formalisms, languages, and tools and explain how they are related. We also provide examples of viewpoints and discuss how they are related to formalisms.