End-To-End Latency of Cause-Effect Chains: A Tutorial

Cyber-Physical Systems (CPS) are being developed to provide useful interactions between physical systems and environments and cyber world for a variety of applications. CPS are designed with a set of software and interconnected distributed hardware components that are linked with physical elements to provide advanced monitoring and control mechanisms geared towards enhancing the targeted physical system or environment. These components function seamlessly to offer specific functionalities that help enhance human lives, physical system operations and environments. While CPS can offer many smart enhancements for improving physical processes, the development of such complex systems composed of many distributed and heterogeneous components is extremely difficult. This is due to the many communication, computing, and networking challenges. Using an appropriate middleware that provides a framework to support developing and operating diverse CPS applications is a novel method to address these challenges. The availability of advanced middleware services and platforms can provide effective approaches for enhancing CPS application development processes as well as provide more robust environments for operating CPS applications. Such middleware can significantly reduce the time needed to design, build, test, and operate robust CPS applications. However, designing a common middleware platform for diverse types of CPS applications is not trivial. This paper investigates the middleware challenges for CPS, based on the different types of CPS applications being developed and their specific challenges. In addition, the paper discusses the current efforts of developing middleware platforms for CPS and the open research issues in the field.

Unmanned aerial vehicles (UAVs) have recently rapidly grown to facilitate a wide range of innovative applications that can fundamentally change the way cyber-physical systems (CPSs) are designed. CPSs are a modern generation of systems with synergic cooperation between computational and physical potentials that can interact with humans through several new mechanisms. The main advantages of using UAVs in CPS application is their exceptional features, including their mobility, dynamism, effortless deployment, adaptive altitude, agility, adjustability, and effective appraisal of real-world functions anytime and anywhere. Furthermore, from the technology perspective, UAVs are predicted to be a vital element of the development of advanced CPSs. Therefore, in this survey, we aim to pinpoint the most fundamental and important design challenges of multi-UAV systems for CPS applications. We highlight key and versatile aspects that span the coverage and tracking of targets and infrastructure objects, energy-efficient navigation, and image analysis using machine learning for fine-grained CPS applications. Key prototypes and testbeds are also investigated to show how these practical technologies can facilitate CPS applications. We present and propose state-of-the-art algorithms to address design challenges with both quantitative and qualitative methods and map these challenges with important CPS applications to draw insightful conclusions on the challenges of each application. Finally, we summarize potential new directions and ideas that could shape future research in these areas.

Cyber-Physical System (CPS) networks represent distributed systems characterized by command, communication, and control elements, acting over the environment in order to fulfill complex interactions with it. The CPS applications need to be robust, error prone and to own dynamically self-reconfigurable and self-maintainable capabilities. In this paper we propose a Linear Programming based approach for solving the computational, error prone detection and dynamical reconfigurable aspects which CPS applications needs to achieve. To illustrate the usage and benefits of this approach, we discuss the design of an aircraft fuel management system implemented using a CPS solution.

In Cyber-Physical Systems (CPS), cyber and physical components must work seamlessly in tandem. Runtime verification of CPS is essential yet very difficult, due to deployment environments that are expensive, dangerous, or simply impossible to use for verification tasks. A key enabling factor of runtime verification of CPS is the ability to integrate real-time simulations of portions of the CPS into live running systems. We propose a verification approach that allows CPS application developers to opportunistically leverage real-time simulation to support runtime verification. Our approach, termed B race B ind , allows selecting, at runtime, between actual physical processes or simulations of them to support a running CPS application. To build B race B ind , we create a real-time simulation architecture to generate and manage multiple real-time simulation environments based on existing simulation models in a manner that ensures sufficient accuracy for verifying a CPS application. Specifically, B race B ind aims to both improve simulation speed and minimize latency, thereby making it feasible to integrate simulations of physical processes into the running CPS application. B race B ind then integrates this real-time simulation architecture with an existing runtime verification approach that has low computational overhead and high accuracy. This integration uses an aspect-oriented adapter architecture that connects the variables in the cyber portion of the CPS application with either sensors and actuators in the physical world or the automatically generated real-time simulation. Our experimental results show that, with a negligible performance penalty, our approach is both efficient and effective in detecting program errors that are otherwise only detectable in a physical deployment.

Cyber-Physical Systems (CPS) intrinsically combine hardware and physical systems with software and network, which are together creating complex and correlated interactions. CPS applications often experience uncertainty in interacting with environment through unreliable sensors. They can be faulty and exhibit runtime errors if developers have not considered environmental interaction uncertainty adequately. Existing work in verifying CPS applications ignores interaction uncertainty and thus may overlook uncertainty-related faults. To improve verification accuracy, in this article we propose a novel approach to verifying CPS applications with explicit modeling of uncertainty arisen in the interaction between them and the environment. Our approach builds an Interactive State Machine network for a CPS application and models interaction uncertainty by error ranges and distributions. Then it encodes both the application and uncertainty models to Satisfiability Modulo Theories (SMT) formula to leverage SMT solvers searching for counterexamples that represent application failures. The precision of uncertainty model can affect the verification results. However, it may be difficult to model interaction uncertainty precisely enough at the beginning, because of the uncontrollable noise of sensors and insufficient data sample size. To further improve the accuracy of the verification results, we propose an approach to identifying and calibrating imprecise uncertainty models. We exploit the inconsistency between the counterexamples’ estimate and actual occurrence probabilities to identify possible imprecision in uncertainty models, and the calibration of imprecise models is to minimize the inconsistency, which is reduced to a Search-Based Software Engineering problem. We experimentally evaluated our verification and calibration approaches with real-world CPS applications, and the experimental results confirmed their effectiveness and efficiency.

Cyberphysical systems (CPSs) are new class of engineered systems that offer close interaction between cyber and physical components. The field of CPS has been identified as a key area of research, and CPSs are expected to play a major role in the design and development of future systems. In this paper, we survey recent advancements made in the development and applications of CPSs. We classify the existing research work based on their characteristics and identify the future challenges. We also discuss the examples of prototypes of CPSs. The aim of this survey is to enable researchers and system designers to get insights into the working and applications of CPSs and motivate them to propose novel solutions for making wide-scale adoption of CPS a tangible reality.

Cyber-physical systems (CPSs) represent a new generation of control systems where distributed local control systems are connected not only physically, but also computationally by means of communication networks. CPSs target introducing intelligence beside traditional monitoring and control functionalities in a way that optimize the performance of the overall system. However, the realization of many CPS applications requires reliable communication systems that provide quality of service (QoS) control. In this domain, Long Term Evolution (LTE) standard offers a comprehensive QoS frame work. Nevertheless, commercial implementations of the standard provide only best effort type of service. In this paper, we demonstrated the benefits of using LTE networks with QoS support for CPSs by comparing the performance of a CPS application over LTE network with and without QoS support. The results clearly indicate the benefit to enable the QoS features in commercial implementations of LTE in order to realize reliable CPS applications.

Cyber-Physical Systems (CPS) refer to systems where some intelligence is embedded into devices that interact with their environment. Using wireless technology in such systems is desirable for better flexibility, improved maintainability, and cost reduction, among others. Moreover, CPS applications often specify deadlines; that is, maximal tolerable delays between the execution of distributed tasks. Systems that guarantee to meet such deadlines are called real-time systems. In the past few years, a technique known as synchronous transmissions (ST) has been shown to enable reliable and energy efficient communication, which is promising for the design of real-time wireless CPS.We identify at least three issues that limit the adoption of ST in this domain: (i) ST is difficult to use due to stringent time synchronization requirements (in the order of μs). There is a lack of tools to facilitate the implementation of ST by CPS engineers, which are often not wireless communication experts. (ii) There are only few examples showcasing the use of ST for CPS applications and academic works based on ST tend to focus on communication rather than applications. Convincing proof-of-concept CPS applications are missing. (iii) The inherent variability of the wireless environment makes performance evaluation challenging. The lack of an agreed-upon methodology hinders experiment reproducibility and limits the confidence in the performance claims. This paper synthesizes recent advances what address these three problems, thereby enabling significant progress for future applications of low-power wireless technology in real-time CPS.

To investigate whether the type of movement cueing influences motor performance in patients with dystonia, we studied externally triggered (ET) and self-initiated (SI) sequential rapid arm movements in patients with generalized or focal dystonia and healthy control subjects. The ET task required subjects to initiate movements in response to consecutive visual cues; the SI task allowed them to start at will. To determine whether patients found sequential motor tasks more difficult than single tasks, we also analyzed single ET movements. Control subjects performed the SI task significantly faster than the ET task. Their single ET movements and first ET sequential submovements had similar speeds. Patients with generalized dystonia were slow in performing the single movement, the ET and the SI sequential tasks, and they executed the SI sequence more slowly than the ET. They made long pauses between SI sequential submovements, had longer reaction times during the ET sequences, and performed the first ET submovement more slowly than the single ET movement. Patients with focal dystonia had normal reaction times but they performed single and sequential tasks slowly, made long pauses during SI tasks, and also executed the first ET submovement more slowly than the single ET movement. Our findings indicate that patients with dystonia have a general impairment of sequential movements. The more marked slowness in executing SI than ET movements observed in patients with generalized dystonia shows that dystonia impairs internal cueing more than external cueing mechanisms. Overall, these findings imply abnormal activation of primary and nonprimary motor areas during movement in dystonia. The greater impairment of SI tasks as well as the delayed motor responses during ET task suggest predominant underactivity of the supplementary motor area.

A cause-effect chain is used to define the logical order of data dependent tasks, which is independent from the execution order of the jobs of the (periodic/sporadic) tasks. Analyzing the worst-case End-to-End timing behavior, associated to a cause-effect chain, is an important problem in embedded control systems. For example, the detailed timing properties of modern automotive systems are specified in the AUTOSAR Timing Extensions. In this paper, we present a formal End-to-End timing analysis for distributed systems. We consider the two most important End-to-End timing semantics, i.e., the button-to-action delay (termed as the maximum reaction time ) and the worst-case data freshness (termed as the maximum data age ). Our contribution is significant due to the consideration of the sporadic behavior of job activations, whilst the results in the literature have been mostly limited to periodic activations. The proof strategy shows the (previously unexplored) connection between the reaction time (data age, respectively) and immediate forward (backward, respectively) job chains. Our analytical results dominate the state of the art for sporadic task activations in distributed systems and the evaluations show a clear improvement for synthesized task systems as well as for a real world automotive benchmark setting.

This paper presents an analysis framework for correct system operation (i.e. system success) of Cyber-Physical Systems (CPS) that deploy binary sensors with possible faults. We discuss potential faults in the interface part of such systems and address solutions for those faults in order to build dependable and reliable CPS applications. As a practical tool, we present a set of models in SIMULINK to help system designers extend simulations of general CPS applications that deploy binary sensor networks. We provide methodologies to add well-defined fault behaviors and offer assessment tools to measure the effects of possible faults on the overall system success. We demonstrate the feasibility of our contributions using a CPS application and explore various architectures for fault mitigation in a holistic design space exploration environment. With the ability to help system designers analyze and assess a non-trivial design space, the presented approach contributes to the design of fault-tolerant CPSs.

The development of the legal framework for ensuring information security of cyber-physical systems in recent years is associated with their widespread use and equipment of industries and households. Various kinds of cyber attacks on cyber-physical systems bring benefits to the attackers in the form of data whose distribution is limited, as well as in the form of the failure of such systems. The article provides statistics on the most common attacks on cyber-physical information systems, as well as the consequences faced by a household or organization. The main stage of the research is the analysis of existing norms of legal regulation of the development and operation of cyber-physical systems. This analysis is the foundation for creating criteria on the basis of which a model for the development of legal support of information security in the field of the functioning of cyber-physical systems can be formed. The result of the research is a formed set of legal measures, the implementation of which will reduce both the number of attacks and the consequences of such attacks on cyber-physical systems.

Cloud computing and its related virtualization technologies have become one of dominant trends to deploy software, compute difficult problems, store different types of data, and stream real-time video and audio. Due to its benefits from cost-efficiency and scalability to maintain server solutions, many organizations are migrating their server applications running on physical servers to virtual servers in cloud computing infrastructures. Moreover, cloud computing has enabled mobile and battery-powered devices to operate without strong processing power and large storage capacity. However, it is not trivial to use this trendy technology for medical Cyber Physical Systems (CPSs) which require processing tasks’ requests to send instructions to the local actuator within specified deadlines. Since a medical CPS device monitoring a patient’s vital signs may not have a second chance to recover from an erroneous state, achieving cost-efficiency with higher resource utilization in cloud computing may not be the ultimate goal to configure the healthcare IT infrastructure with medical CPS devices. In this paper, we focus on private cloud infrastructures with the fair resource sharing mechanism in order to run medical CPS applications. First, we introduce our medical CPS device model used for designing our cloud infrastructure following the Integrated Clinical Environment (ICE) standard developed by the Medical Device Plug-and-Play (MDPnP) project. Second, we investigate limitations to deploy CPS applications using existing auto-scaling mechanisms. Finally, we propose our novel middleware with a virtual resource sharing mechanism inspired by autonomic computing, and present its performance evaluation results simulated in the OpenStack private cloud.

The focus of the current chapter is on humanoid robots as part of an inclusive education. It presents a brief overview of the main features of cyber physical systems which could be used as an advantage with children with special educational needs. Based on the specifics of the main types of special educational needs, a list of suggestions about the practical implications of educational robots to the classroom has been generated. A pilot study of the perception and attitude of children and teachers in a local Bulgarian school towards the application of cyber physical systems in education has been conducted. Based on previous research and the fundings of the pilot study, a few gaps of knowledge have been identified. First, the lack of empirical work on the application of technology to subjects, such as biology, chemistry, history, or to the development of social skills and creativity. Second, the scarce evidence of the long-term effects of interventions with children with special educational needs. Third, the lack of research on the attitudes of teachers with and without special educational needs children in the class towards educational robots. Last, but not least, the need for comparison of the perceptions and expectations of users of such technology across cultures.

The positioning navigation and timing (PNT) architecture was discussed in detail, whose history, evolvement, current status and future plan were presented, main technologies were listed, advantages and limitations of most technologies were compared, novel approaches were introduced, and future capacities were sketched. The concept of cyber-physical system (CPS) was described and their primary features were interpreted. Then the three-layer architecture of CPS was illustrated. Next CPS requirements on PNT services were analyzed, including requirements on position reference and time reference, requirements on temporal-spatial error monitor, requirements on dynamic services, real-time services, autonomous services, security services and standard services. Finally challenges faced by PNT applications in CPS were concluded. The conclusion was expected to facilitate PNT applications in CPS, and furthermore to provide references to the design and implementation of both architectures.