Reconfigurable Real-Time Middleware for Distributed Cyber-Physical Systems with Aperiodic Events

The Internet of Things (IoT) is transforming various domains, including smart energy management, by enabling the integration of complex digital and physical components in distributed cyber-physical systems (DCPSs). The design of DCPSs has so far been focused on performance-related, non-functional requirements. However, with the growing power consumption and computation expenses, sustainability is becoming an important aspect to consider. This has led to the concept of energy-aware DCPSs, which integrate conventional non-functional requirements with additional attributes for sustainability, such as energy consumption. This research activity aimed to investigate and develop energy-aware architectural models and edge/cloud computing technologies to design next-generation, AI-enabled (and, specifically, deep-learning-enhanced), self-conscious IoT-extended DCPSs. Our key contributions include energy-aware edge-to-cloud architectural models and technologies, the orchestration of a (possibly federated) edge-to-cloud infrastructure, abstractions and unified models for distributed heterogeneous virtualized resources, innovative machine learning algorithms for the dynamic reallocation and reconfiguration of energy resources, and the management of energy communities. The proposed solution was validated through case studies on optimizing renewable energy communities (RECs), or energy-aware DCPSs, which are particularly challenging due to their unique requirements and constraints; in more detail, in this work, we aim to define the optimal implementation of an energy-aware DCPS. Moreover, smart grids play a crucial role in developing energy-aware DCPSs, providing a flexible and efficient power system integrating renewable energy sources, microgrids, and other distributed energy resources. The proposed energy-aware DCPSs contribute to the development of smart grids by providing a sustainable, self-consistent, and efficient way to manage energy distribution and consumption. The performance demonstrates our approach's effectiveness for consumption and production (based on RMSE and MAE metrics). Our research supports the transition towards a more sustainable future, where communities adopting REC principles become key players in the energy landscape.

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This paper derives fundamental bounds on privacy achievable in future human-centric cyber-physical systems, where time-series sensor data are shared among individuals to compute aggregate information of mutual interest. For example, individual GPS-trajectories may be shared to compute average traffic speed at different locations. An optimal trade-off is explored between individual user privacy, achieved by perturbing data prior to sharing, and the corresponding accuracy of computed aggregate information. The work is motivated by an emergent category of cyber-physical applications that involves large-scale interaction between humans, networked engineered artifacts, and the physical world. These applications are brought about by the proliferation of personal sensing devices of everyday use, leading to unprecedented opportunities for sensory data collection and sharing. The collection of sensory data from large numbers of participants offers privacy as a major new cyber-physical system challenge. In this paper, we propose a novel privacy measure, based on mutual information, and derive a perturbation algorithm, to apply prior to data sharing, that guarantees a least upper bound on the privacy measure. The new algorithm effectively hides individual user data by optimally perturbing the time-series using knowledge of only the mean and the covariance of the original data. We evaluate it using both synthetic data and collected real application data. The results show that the method significantly improves the trade-off between privacy and the accuracy of reconstruction of aggregate information from shared perturbed data.

The recent deployment of Cyber-Physical Systems (CPS) has emerged as the most promising approach to provide an extensive computational capability for processing and controlling physical entities, which relies on reliable data exchanges among machines in CPS. However, for CPS exploiting public network infrastructures, links in CPS may suffer from a variety of vulnerabilities to harm real-time data exchanges. Providing network resilience for real-time communications consequently becomes the most critical requirement in CPS. Considering the support of multiple communication paths in state-of-the-art network infrastructures, in this paper, we develop a mathematical resource-optimal network resilience design for CPS. In our design, duplicates of timing sensitive data are simultaneously forwarded via multiple communication paths. Therefore, timing constraints are violated only if all communication paths fail to forward data to the destination on time. By analyzing the relationship among the probability of timing constraint violation, the time domain resource allocation, and the number of communication paths (the spatial domain resource allocation), our design leads to the minimum resource usage to support real-time data exchanges in CPS. Our mathematical resource-optimal design solves the most challenging issue of unreliable data exchanges in CPS in the most efficient fashion, to consequently support the maximum number of machines in CPS.

Current group communication services have mostly been implemented on a homogeneous, distributed computing environment. This limits their applicability because most modern distributed computing environment are heterogeneous in nature. This paper describes the design, implementation, and performance evaluation of a CORBA group communication service. Using CORBA to implement a group communication service enables that group communication service to operate in a heterogeneous, distributed computing environment. To evaluate the effect of CORBA on the performance of a group communication service, this paper provides a detailed comparison of the performance measured from three implementations of an atomic broadcast protocol and a group membership protocol. Two of these implementations use CORBA, while the third uses UDP sockets for interprocess communication. The main conclusion is that heterogeneity can be achieved in group communication services by implementing them using CORBA, but there is a substantial performance cost. This performance cost can be reduced to a certain extent by carefully choosing a design and tuning various protocol parameters such as buffer sizes and timer values.

Cyber Physical Systems are in charge of the control of physical processes characterized by their own dynamics. This control must comply with timing constraints - sometimes stringent ones-imposed by the Cyber Physical Systems. It is crucial to address these timing issues as early as possible in the development process to detect inconsistencies in the requirements or in the constraints and to capture changes in the system. This paper aims to apply the clock theory to the specification of Cyber Physical Systems. To illustrate the concept we develop three well-known case studies: the Steam Boiler Control System, Press and Railway Cross System.

The study aims to describe the implementation of a primary practitioner physiotherapy service within a large regional ED and to evaluate its impact on waiting time and length of stay. Integration and scope of practice of the physiotherapy service within the ED were described. Retrospective analysis of waiting time and length of stay data for the 3 years, 1 October 2008 to 30 September 2011, was performed. The performance of the physiotherapy service was compared with the Australasian College for Emergency Medicine (ACEM) waiting time guidelines, the Victorian Department of Health length of stay targets and to a similar group of patients seen by medical staff. The primary practitioner physiotherapy service saw 5641 patients of which 33% were less than 18 years old. The most common presentations seen by the service were limb fractures, soft tissue injuries and low back pain. Ninety-two per cent of patients were seen within the ACEM waiting time guidelines, and 91% of patients who went home were discharged within 4 h. Non-randomised comparisons with similar patients seen by medical staff indicated that patients seen by the physiotherapy practitioner service had shorter waiting times and length of stay. The current study found that patients with musculoskeletal problems seen by a primary practitioner physiotherapy service had improved waiting times and length of stay relative to ACEM and Victorian Department of Health targets, and though constrained by a retrospective non-randomised design, to a similar group of patients seen by medical staff. Further evaluation of the physiotherapy practitioner service is required.

With the increasing dependencies on Information and Communication Technologies (ICTs), the smart distribution system has similar characteristics to Cyber-Physical System (CPS) and is seen as the so-called “cyber-physical power system” (CPPS). However, the impact of upstream substation is becoming one of the main factors impacting on distribution reliability. To avoid the too optimistic conclusion, the Cyber-Induced Dependent Failures (CDFs) of upstream substation are important to be considered. Thus the cyber security risk brought by both the malfunction of ICT components and the cyber-attack should be taken into account. This paper provided a methodology to incorporate both the two sides of CDFs in upstream substation into cyber-enabled distribution system reliability assessment. In the sequential Monte Carlo simulation (MCS), the game process between attackers and defenders can be modelled as the semi-Markov Chain (SMP), and indices are calculated by the minimal path method. The effects of CDFs are quantified and converted onto the joint feeders, based on the Breadth-First-Search (BFS), as well. Some conclusions for the distribution and substation automation planning have been made and verified by the cyber-extended Roy Billinton Test System (RBTS).

Real-time CORBA is a middleware standard that has demonstrated successes in developing distributed, realtime, and embedded (DRE) systems. Customizing real-time CORBA for an application can considerably reduce the size of the middleware and improve its performance. However, customizing middleware is an error-prone task and requires deep knowledge of the CORBA standard as well as the middleware design. This paper presents ZEN-kit, a graphical tool for customizing RTZen (an RTSJ-based implementation of real-time CORBA). This customization is achieved through modularizing the middleware so that features may be inserted or removed based on the DRE application requirements. This paper presents three main contributions: 1) it describes how real-time CORBA features can be modularized and configured in RTZen using components and aspects, 2) it provides a configuration strategy to customize real-time middleware to achieve low-footprint ORBs, and 3) it presents ZEN-kit, a graphical tool for composing customized real-time middleware.

Wireless communications have been widely deployed to collect and disseminate data for industrial applications. However, to date the mostly accepted technologies for information collection and dissemination in power grid are still based on wired communications instead of wireless. To leverage the advantages of wireless communications for smart grid, proper wireless networks need to be designed to satisfy the specific service requirements of power grid. Considering the diverse service requirements in different applications of power grid, the design of a wireless network is usually application-specific. So far no systematic approach is available to guide the design of smart grid wireless networks. To this end, a systematic approach is developed in this paper to provide guidelines for smart grid wireless communications. It is based on the framework of cyber-physical system (CPS). Under this framework, a smart grid wireless communication system is categorized into either a loosely-coupled or closely-coupled CPS, considering different mechanisms of interaction between a wireless network and power grid. For either CPS, general procedures of wireless network design are proposed by considering the service requirements and unique features of such a CPS. To illustrate how these design procedures are applied in reality, two application scenarios are presented to demonstrate smart grid wireless communications based on loosely-coupled CPS and closely-coupled CPS, respectively.

Cyber physical systems have many non-functional requirements, which always crosscut the whole system modules. That may cause the code tangle and scatter, make the systems hard to design, reuse and maintain, and affect performance of systems badly. AOP is a new software development paradigm, which could attain a higher level of separation of concerns in both functional and non-functional matters by introducing aspect, for the implementation of crosscutting concerns. Different aspects can be designed separately, and woven into systems. In this paper, we propose a four-stage method of aspect-oriented MDA for non-functional properties to develop cyber physical systems. The model-based development, aspect-oriented approach and formal methods are integrated effectively for the development of the non-functional properties of distributed cyber physical systems. A case study illustrates the aspect oriented MDA development of cyber physical systems.

Recently, there has been a large-scale integration of renewable sources to keep pace with the enormous increment of consumers’ load demand. The integration of these devices on a large scale can violate the technical and regulatory constraints of the smart power grid. Therefore, a proper control system must be designed to increase their power output and maximize the system owners’ benefit while meeting power grid standards. This paper is a collection of information to provide its reader with a holistic view of the implementation of a cyber-physical system to aid in distribution system planning. The goal of this paper is to review the current literature and identify research gaps that have yet to be fully explored. This is followed by making proposals for areas to be researched in order to improve the knowledge bank surrounding this important topic. This paper will begin by addressing the concept of a cyberphysical system by elaborating on its structure through its various layers. It will also describe the role of the Internet of Things (IoT) in improving the monitoring and control abilities of cyber-physical distribution systems. Furthermore, a detailed literature review is given to highlight the current state of distribution system research being done surrounding the implementation of cyber-physical systems to improve system planning. Based on this review, an analysis is given to better explain how a successful cyber-physical based distribution system can be constructed to achieve automation. Finally, gaps in current research are discussed to provide an understanding on which aspects of cyber-physical based distribution system planning have not been fully explored yet and where more exploration needs to be done. A list of research questions are provided to help aid potential researchers dive deeper into the area of fully automating distribution systems that consist of both renewable and non-renewable sources of energy.

Cyber physical systems are envisioned to integrate computation, control and communication with the physical environment. Therefore, CPS requires strong interactions between the cyber and physical worlds in time. The design of cyber physical systems (CPS) poses many challenges because of their complexity, high safety requirements, distribution, and real time nature. We propose a novel paradigm, based on the idea of using simplicity of the aspect-oriented MDA design method to control complexity, to achieve highly correct CPS designs. The model-based development, aspect-oriented approach and formal methods are integrated effectively for the development of the non-functional properties of distributed cyber physical systems. A case study illustrates the aspect oriented MDA development of cyber physical systems.

The complexity of today's embedded and cyber-physical systems is rapidly increasing and makes the consideration of higher levels of abstraction during the design process inevitable. In this context, the impact of modeling languages such as UML and its profiles such as MARTE is growing. Here, CCSL provides a formal description of timing constraints which have to be enforced on the considered system. This builds the basis for many further design steps and can be used e. g. for checking the consistency of the specification, for code generation, or for proving whether the time constraints have correctly been implemented at lower abstraction levels. However, most of the approaches available thus far usually focus on sole design tasks only -- often even without an explicit consideration of the system's functional behavior. In this work, we are aiming for overcoming this drawback by providing a method to automatically generate a generic representation of a set of clock constraints in terms of a transition relation. Afterwards, the resulting transition relation can easily be utilized for the above mentioned design tasks. A discussion on the applicability of the generic description as well as an exemplary evaluation shows the promise of the proposed generic representation.

Bounded model checking for interval probabilistic timed graph transformation systems against properties of probabilistic metric temporal graph logic