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This paper investigates the secure optimal tracking control problem for cyber-physical systems, in which the controller-actuator channel is jammed by denial-of-service attacks. Without leveraging model knowledge, learning-based tracking control algorithms are proposed by utilizing the measured input-output data. The impact of malicious attacks on tracking performance is discussed. More specifically, an augmented system consisted of the system model and the reference model is derived. Then the states of the augmented system are rewritten by utilizing the input, output, and reference trajectory, following which both the Bellman equation and algebraic Riccati equation are given. The conditions of existence and uniqueness of the solution to the algebraic Riccati equation are derived. Furthermore, both policy iteration and value iteration learning-based tracking control algorithms are provided for cyber-physical systems against denial-of-service attacks, and the convergence of the algorithms is also proved. Finally, a DC motor system and a numerical example are given to illustrate the effectiveness of the proposed control algorithms. [ABSTRACT FROM AUTHOR]

In this paper, a Lyapunov-based design method for event-triggered control with self-triggered sampling is proposed. In the proposed method, update of the control input and sampling of the state are individually determined based on two kinds of upper bounds of the Lyapunov function. By the proposed method, a non-monotonic Lyapunov function can be constructed. By non-monotonic decrease of a Lyapunov function, the number of communications can be reduced. In the neighborhood of the origin, we consider a control method such that the state stays in a certain set. As a result, it is guaranteed that the closed-loop system is uniformly ultimately bounded. Through a numerical example, we demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, we address the problem of developing a unified method for quantifying and improving the cyber resilience of large-scale cyber-physical systems (CPSs) against cyber-attacks targeting structural controllability. To this end, we provide necessary and sufficient conditions to extend the concept of structural controllability of single-layer systems to two-layer CPSs comprising of power network as the physical layer and communication network as the cyber layer. Next, in order to assess cyber resilience, we introduce the notion of $ R $ R -resilient CPS as the maximum number of cyber nodes that can be attacked by an adversary while preserving the structural controllability of the entire CPS. Furthermore, we provide an algorithm to find the optimal network reconfiguration matrix to increase the resilience level of CPS from $ R $ R -resilient to $ ({R + 1}) $ (R + 1) -resilient by adding a minimum number of transmission lines to the physical layer or communication links to the cyber layer, or both. Additionally, the proposed methodology is extended to achieve $ ({R + \alpha }) $ (R + α) -resilient CPS, where α>1. The effectiveness of the proposed method is verified through simulations of IEEE 14, IEEE 39, and IEEE 118 power networks with different cyber topologies, considering four scenarios of denial-of-service (DoS) attacks, including targeted and random node attacks. [ABSTRACT FROM AUTHOR]

This paper investigates the secure state estimation problem of the cyber-physical systems (CPSs) in the presence of malicious attacks. Considering the destructiveness and stealthiness of the attacker, a novel stochastic transmission scheme, in which the repeater generates transmission data by randomly combining some measurement values, is proposed to ensure the effectiveness of the attack detector. A filter equipped with the $ \chi ^2 $ χ 2 detector and the stochastic transmission scheme is proposed to conduct the secure state estimation. The attack probability condition of the estimation error being mean-square bounded is given, which indicates that stochastic transmission scheme has a limited effect on the filter. Some numerical simulations are given to illustrate the effectiveness of the proposed transmission scheme. [ABSTRACT FROM AUTHOR]

Wireless sensor networks, which play a significant role in monitoring complex environments that change rapidly over time, were used in the Artificial Intelligence method. External factors or the device designers themselves are both responsible for this complex behavior. Sensor networks often use machine learning techniques to adapt to such conditions, eliminating the need for excessive redesign. Cyber-physical systems (CPS) appeared as the promising option for improving physical-virtual interactions. The quality of the system containing processing information is primarily determined by the system function. There are many benefits obtained while combining Artificial Intelligence (AI) and Cyber-Physical Systems (CPSs) in buildings. In CPS-based indoor environment has various design schemes containing measurement and intelligent buildings in the control system consisting of detection, tracking, execution, and communication modules. The Multi-Agent System (MAS) is the smallest control unit that simulates among neurons and it flexibly provides the information. To mimic the interactions between human neurons, multi-agents are used. In this paper, the CPS's information world is built on the fundamental principle of granular formal concepts and the theory of granular computing is investigated. The calculation module is used by Back-Propagation Neural Network (BPNN) for pattern recognition and classification by environmental information. Various parameters namely the normalized root mean square error, peak signal-to-noise ratio, mean square error, and the mean absolute error are chosen as the objective assessment criteria to assess the benefits of the proposed method and the effectiveness of the proposed system is proven. [ABSTRACT FROM AUTHOR]

Cyber-Physical Systems (CPSs) require the interfacing of two different time domains: (1) the physical time-continuous domain and (2) the computational time-discrete domain. The Nyquist-Shannon sampling theorem allows transitions from one domain to the other. To preserve the informational signal between both domains, strictly periodic sampling, also known as uniform spaced sampling, is required. CPSs utilise real-time systems to meet temporal constraints. However, real-time systems introduce jitter when several tasks are executed; consequently, the uniform spaced sampling is jeopardized. The Paley-Wiener-Levinson theorem should be used for non-uniform spaced sampling, but its complexity makes it unsuitable for runtime execution in CPSs. Jitter in real-time systems may cause perturbations in CPS applications. In this paper, frequency domain methodologies are proposed to analyse the perturbations introduced by real-time systems in physical applications. It is shown that jitter may introduce frequency components with the potential to jeopardize the dynamics of the physical application. In this paper, it is proposed that jitter should be related to the period of the fundamental frequency to sample, instead of to the period of the real-time task. The frequency domain methodology proposed should be used to analyse the real-time system behaviour from a CPS application point of view. [ABSTRACT FROM AUTHOR]

In this paper, the distributed mixed H 2 / H ∞ fusion filter design problem is investigated for a class of cyber-physical systems subject to non-ideal measurements under Round-Robin protocol. To save the limited communication resources, the Round-Robin protocol is employed to schedule the data transmissions from the sensors to the remote filters. The measurement is imperfect by taking into account the noises, the random saturations, nonlinearity perturbations and packet dropouts. The objective of this study is to propose a desired fusion filtering method that ensures the prescribed performance constraints on both the local and fusion filtering error dynamics. With the aid of Lyapunov function and stochastic analysis technique, a sufficient condition is established to guarantee the mixed H 2 / H ∞ performance index for the local filtering error systems, and then the filter parameter matrices are derived by resorting to the solutions to some matrix inequalities. Subsequently, on the basis of the obtained local state estimates, the proper fusion parameters are acquired by solving a convex optimisation problem. Finally, a numerical example is provided to demonstrate the effectiveness of the designed fusion filter. [ABSTRACT FROM AUTHOR]

The Fourth Industrial Revolution, also known as Industry 4.0, stems from the rapid advancement of digital technologies such as the Internet of Things and Cyber-Physical Production Systems. It has the potential to weave positive changes to firms and impact organizational structure layers. Therefore, it provides an impetus for the collaboration of factories, suppliers, and customers. Nevertheless, due to the difference of Industry 4.0 vision among companies, there is a lack of unified perception and approach of its implementation roadmap. Therefore, many firms in both developed and developing countries that step in the way of digital transformation encounter not only organizational, technological, and operational challenges but are also compelled to cope with a large deal of confusion. Hence, this paper aims to identify the main concepts, characteristics, and technology enablers related to Industry 4.0 to provide stakeholders with a clear understanding of this paradigm. It then clusters and matches the derived concepts and characteristics associated with Industry 4.0. Further, the paper provides an analysis of how these clusters are supported by technology enablers of Industry 4.0, as well as managerial implications. [ABSTRACT FROM AUTHOR]

Safety-critical cyber-physical systems (SC-CPS) have the characteristics of distributed, heterogeneous, strong coupling of computing resources and physical resources. With the increased acceptance of Model-Driven Development (MDD) in the safety-critical domain, the SysML language has been broadly used. Increasing complexity results in the formal verification of the SysML models of SC-CPS often faces the so-called state-explosion problem. Moreover, safety analysis is also an important step to ensure the quality of SC-CPS. Thus, this article proposes an integrated SysML modelling and verification approach to cover specification of nominal behaviour and safety. First, an extension of SysML is presented, in which the contract information (i.e. Assume and Guarantee) is extended for SysML block diagrams and a Safety Profile is proposed to describe safety-related concepts. Second, the transformation from SysML to the compositional verification tool OCRA is given. Third, the safety analysis is achieved by translating the Safety Profile model into FTA (Fault Tree Analysis). Finally, the prototype tools including SysML2OCRA and SafetyProfile2FTA are represented, and the effectiveness of the method proposed in this paper is verified through actual industrial cases. [ABSTRACT FROM AUTHOR]

Cyber-Physical Systems (CPSs), with the intrinsical vulnerability of the cyber layer, are always suffering from malicious data injection (DI) attacks. In this paper, switched counteraction principle based defense strategies are designed for secure state estimation (SSE) of CPSs under sparse DI attacks. Firstly, the physical layer is modelled by a hybrid mechanism, based on which malicious injections are excluded by implementing adaptively switched counteraction searching. Sufficient conditions are established to ensure the feasibility of SSE design. Next, by set cover approach, a defence strategy is presented to further relax the computation burden caused by combinational brute force search. Two numerical examples are given to illustrate the effectiveness and potential of the proposed design methods. [ABSTRACT FROM AUTHOR]

Cyber-Physical Systems (CPSs) use sensors and actuators to interface between an embedded system and the physical world. The time-continuous domain of the physical world should be periodically sampled by real-time tasks in an embedded system to preserve its dynamic properties in the time-discrete domain. Because the task execution pattern may vary during runtime, a jitter in the execution of a real-time task hinders the periodicity of its execution. The effects of jitters in CPSs are difficult to determine when the premises of the Nyquist-Shannon sampling theorem are not satisfied. This paper proposes using frequency domain analysis to determine the perturbations that a real-time system produces on real-world applications; accordingly, the paper defines both a design and an evaluation criterion for real-time systems in CPS applications. The Fixed Priority discipline is analysed through simulations to conclude that no special design techniques are required when the utilization factors are less than 20%. [ABSTRACT FROM AUTHOR]

Safety-critical cyber-physical systems (SC-CPS) have the characteristics of distributed, heterogeneous, strong coupling of computing resources and physical resources. With the increased acceptance of Model-Driven Development (MDD) in the safety-critical domain, the SysML language has been broadly used. Increasing complexity results in the formal verification of the SysML models of SC-CPS often faces the so-called state-explosion problem. Moreover, safety analysis is also an important step to ensure the quality of SC-CPS. Thus, this article proposes an integrated SysML modelling and verification approach to cover specification of nominal behaviour and safety. First, an extension of SysML is presented, in which the contract information (i.e. Assume and Guarantee) is extended for SysML block diagrams and a Safety Profile is proposed to describe safety-related concepts. Second, the transformation from SysML to the compositional verification tool OCRA is given. Third, the safety analysis is achieved by translating the Safety Profile model into FTA (Fault Tree Analysis). Finally, the prototype tools including SysML2OCRA and SafetyProfile2FTA are represented, and the effectiveness of the method proposed in this paper is verified through actual industrial cases. [ABSTRACT FROM AUTHOR]

Emerging industrial platforms such as the Internet of Things (IoT), Industrial Internet (II) in the US and Industrie 4.0 in Europe have tremendously accelerated the development of new generations of Cyber-Physical Systems (CPS) that integrate humans and human organizations (H-CPS) with physical and computation processes and extend to societal-scale systems such as traffic networks, electric grids, or networks of autonomous systems where control is dynamically shifted between humans and machines. Although such societal-scale CPS can potentially affect many aspect of our lives, significant societal strains have emerged about the new technology trends and their impact on how we live. Emerging tensions extend to regulations, certification, insurance, and other societal constructs that are necessary for the widespread adoption of new technologies. If these systems evolve independently in different parts of the world, they will 'hard-wire' the social context in which they are created, making interoperation hard or impossible, decreasing reusability, and narrowing markets for products and services. While impacts of new technology trends on social policies have received attention, the other side of the coin – to make systems adaptable to social policies – is nearly absent from engineering and computer science design practice. This paper focuses on technologies that can be adapted to varying public policies and presents (1) hard problems and technical challenges and (2) some recent research approaches and opportunities. The central goal of this paper is to discuss the challenges and opportunities for constructing H-CPS that can be parameterized by social context. The focus in on three major application domains: connected vehicles, transactive energy systems, and unmanned aerial vehicles. Abbreviations: CPS: Cyber-physical systems; H-CPS: Human-cyber-physical systems; CV: Connected vehicle; II: Industrial Internet; IoT: Internet of Things [ABSTRACT FROM AUTHOR]

In this paper, the important issue is proposed, that is, the robust control of a class of cyber-physical systems (CPSs) in the complex environment where unknown disturbances, unknown bounded delays and stochastic malicious attacks coexist. A Lyapunov–Krasovskii functional (LKF) containing certain double and triple integral terms is constructed to exploit merits of the presented generalised single and double integral inequalities which are tighter than some existing single and double inequalities, leading to the stability analysis result with less conservatism. Furthermore, by using stochastic analysis technique, the stability analysis and H ∞ output feedback controller design are transformed into the convex optimisation problems solved by the linear matrix inequality (LMI) strategy. Finally, the actual load frequency control (LFC) power system and the classical numerical examples are provided to show the rationality for modelling and the advancement of the developed method. [ABSTRACT FROM AUTHOR]

This paper is concerned with the distributed secure estimation problem for a cyber-physical system (CPS) with fading measurements and false data injection (FDI) attacks, where the fading probability of measurements is assumed to be individual for each sensor, and the FDI attacks occur at the physical system layer to intensively modify the system's state. For improving security of the system, an attack detection mechanism is proposed based on an FDI attack observer constructed by minimising the upper bound of observation error covariance. Then a complete distributed state estimation algorithm is given to provide locally reliable estimation. A sufficient condition is provided to guarantee boundedness of the estimation error covariance. Finally, the effectiveness of the proposed method is illustrated by numerical simulation and practical example simulation. [ABSTRACT FROM AUTHOR]

Cyber-Physical Systems (CPS) is a new generation of digital technology that is concerned with the integration and inter-dependencies of the cyber and physical world alongside computational elements. As a new and leading technology, its applications are seen in different projects involving energy and this has however generated lots of interest from the industry, researchers in academia and the government. This paper presents an extensive overview and modernistic research on the applications relating to energy CPS and the security issues and challenges revolving around this research path. In order to achieve this, a systematic literature review was carried out which enabled the analysing and classifying of different applications and security issues described in selected publications. Furthermore, the systematic review permitted the discourse stringing these research areas as well as providing future lines of research. Also, results from the review show the paths where there are increasing research focus and expected research trend in the future years to come. These results will not only be useful in serving as a guide to researchers but will also create new research paths to more experienced researchers to actively follow. [ABSTRACT FROM AUTHOR]

Security issues of cyber-physical systems have received increasing attentions in recent years. In this paper, deception attacks on the remote state estimator equipped with the chi-squared failure detector are considered, and it is assumed that the attacker can monitor and modify all the sensor data. A novel adaptive optimisation-offline cyber attack strategy is proposed, where using the current and previous sensor data, the attack can yield the largest estimation error covariance while ensuring to be undetected by the chisquared monitor. From the attacker's perspective, the attack is better than the existing linear deception attacks to degrade the systemperformance. Finally, some numerical examples are provided to demonstrate theoretical results. [ABSTRACT FROM AUTHOR]

Cradle to grave product support has been a key issue in the engineering sector over many years, particularly because product engineering legacy knowledge is often lost during the product development process unless rigorously captured in some way. This is particularly the case during formal design reviews at any point during a product's lifecycle where engineering changes are not fully documented or where salient but important aspects of decision making are difficult to document explicitly. Though many software systems are available to support design reviews, they have not necessarily met the expectations of industry. Consequently, traditional knowledge capture methods tend to be time-consuming, costly and disruptive leading to many companies simply giving up on this crucial aspect of product development. This paper presents research carried out with regard to prototyping and testing a potential knowledge engineering capture and reuse solution, demonstrating real-time user-logging using virtual design environments focused on team-based design ‘reviews’. Called the Virtual Aided Design Engineering Review (VADER) system, it provides millisecond precision time-phased knowledge capture in an automatic and unobtrusive manner. Both structured and unstructured data are synthesised via a ubiquitous integration and temporal synchronisation (UbiITS) framework that enables interactive information mapping, retrieval and mining. VADER's frontend includes a virtual reality based 3D model view display as a multiuser collaborative interface and an auxiliary web interface for concurrent access by multiple distributed users during product design discussions. Feedback from engineers using the system demonstrated that this concept is one which believe would substantially enhance their engineering task knowledge capture, rapid retrieval and reuse capability. It was also surmised that, if required, such a system can be extended throughout the whole product development process capturing individual and team-based engineers’ inputs across the whole cradle-to-grave product life cycle. Also, due to its generic nature, this approach is not limited only to engineering applications or virtual environments but can potentially be used in other sectors using computer-based technologies of any kind. [ABSTRACT FROM PUBLISHER]