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Special Issue "Cyber-Physical Systems"

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A special issue of Sensors (ISSN 1424-8220). This special issue belongs to the section "Sensor Networks".

Deadline for manuscript submissions: closed (30 June 2015)

Special Issue Editor

Guest Editor
Prof. Dr. Albert M. K. Cheng (Website)

Department of Computer Science University of Houston Houston, TX77004, USA
Interests: real-time and embedded systems, functional reactive programming, real-time virtualization, cyber-physical systems, power-aware computing, formal verification, real-time logic, rule-based systems

Special Issue Information

Dear Colleagues,

A cyber-physical system (CPS) is a tightly coupled integration and coordination of computing elements, communication components, and physical resources. A multitude of wired and/or wireless communication/sensor networks connect these computing elements and physical resources. It is insufficient to study each of the following in isolation since a CPS is not their union, but their intersection: embedded computers, control theory, sensor and communication networks, physical resources, decision theory, data fusion, and knowledge discovery. Their joint dynamics must be studied together and this is what set this emerging discipline apart from these individually established fields. Before deploying a CPS, a formal modeling, analysis, and verification must be performed on the entire system, as well as its components, to ensure the CPS's safety, performance, and resilience. This Special Issue is devoted to the latest research in CPS and solicits papers in the following (but not limited to) topics:

  • Real-Time and Embedded Systems
  • Design Space Exploration and Synthesis
  • Control and Optimization
  • Automatic Optimization of Specifications and in Compilers, and Code Generators
  • Timing and Performance Analysis
  • Timing Analysis of Functional reactive systems
  • Model-based Testing
  • Correct-by-Construction
  • Requirements Modeling and Analysis
  • Model-driven Engineering
  • Application of Formal Methods in the design and validation of embedded systems
  • Safety Analysis
  • Fault Tolerance and Resilience
  • Sensor Networks
  • Code Generator Verification
  • Machine Learning
  • Data Fusion and Mining
  • Security

Dr. Albert M. K. Cheng
Guest Editor

Submission

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Sensors is an international peer-reviewed Open Access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs).

Published Papers (21 papers)

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Open AccessArticle An Energy-Efficient Skyline Query for Massively Multidimensional Sensing Data
Sensors 2016, 16(1), 83; doi:10.3390/s16010083
Received: 29 September 2015 / Revised: 7 December 2015 / Accepted: 6 January 2016 / Published: 9 January 2016
Cited by 1 | PDF Full-text (1926 KB) | HTML Full-text | XML Full-text
Abstract
Cyber physical systems (CPS) sense the environment based on wireless sensor networks. The sensing data of such systems present the characteristics of massiveness and multi-dimensionality. As one of the major monitoring methods used in in safe production monitoring and disaster early-warning applications, [...] Read more.
Cyber physical systems (CPS) sense the environment based on wireless sensor networks. The sensing data of such systems present the characteristics of massiveness and multi-dimensionality. As one of the major monitoring methods used in in safe production monitoring and disaster early-warning applications, skyline query algorithms are extensively adopted for multiple-objective decision analysis of these sensing data. With the expansion of network sizes, the amount of sensing data increases sharply. Then, how to improve the query efficiency of skyline query algorithms and reduce the transmission energy consumption become pressing and difficult to accomplish issues. Therefore, this paper proposes a new energy-efficient skyline query method for massively multidimensional sensing data. First, the method uses a node cut strategy to dynamically generate filtering tuples with little computational overhead when collecting query results instead of issuing queries with filters. It can judge the domination relationship among different nodes, remove the detected data sets of dominated nodes that are irrelevant to the query, modify the query path dynamically, and reduce the data comparison and computational overhead. The efficient dynamic filter generated by this strategy uses little non-skyline data transmission in the network, and the transmission distance is very short. Second, our method also employs the tuple-cutting strategy inside the node and generates the local cutting tuples by the sub-tree with the node itself as the root node, which will be used to cut the detected data within the nodes of the sub-tree. Therefore, it can further control the non-skyline data uploading. A large number of experimental results show that our method can quickly return an overview of the monitored area and reduce the communication overhead. Additionally, it can shorten the response time and improve the efficiency of the query. Full article
(This article belongs to the Special Issue Cyber-Physical Systems)
Open AccessArticle TF4SM: A Framework for Developing Traceability Solutions in Small Manufacturing Companies
Sensors 2015, 15(11), 29478-29510; doi:10.3390/s151129478
Received: 20 July 2015 / Revised: 26 October 2015 / Accepted: 18 November 2015 / Published: 20 November 2015
Cited by 3 | PDF Full-text (1324 KB) | HTML Full-text | XML Full-text
Abstract
Nowadays, manufacturing processes have become highly complex. Besides, more and more, governmental institutions require companies to implement systems to trace a product’s life (especially for foods, clinical materials or similar items). In this paper, we propose a new framework, based on cyber-physical [...] Read more.
Nowadays, manufacturing processes have become highly complex. Besides, more and more, governmental institutions require companies to implement systems to trace a product’s life (especially for foods, clinical materials or similar items). In this paper, we propose a new framework, based on cyber-physical systems, for developing traceability systems in small manufacturing companies (which because of their size cannot implement other commercial products). We propose a general theoretical framework, study the requirements of these companies in relation to traceability systems, propose a reference architecture based on both previous elements and build the first minimum functional prototype, to compare our solution to a traditional tag-based traceability system. Results show that our system reduces the number of inefficiencies and reaction time. Full article
(This article belongs to the Special Issue Cyber-Physical Systems)
Open AccessArticle A Model-Based Approach to Support Validation of Medical Cyber-Physical Systems
Sensors 2015, 15(11), 27625-27670; doi:10.3390/s151127625
Received: 30 June 2015 / Revised: 11 October 2015 / Accepted: 16 October 2015 / Published: 30 October 2015
Cited by 1 | PDF Full-text (5759 KB) | HTML Full-text | XML Full-text
Abstract
Medical Cyber-Physical Systems (MCPS) are context-aware, life-critical systems with patient safety as the main concern, demanding rigorous processes for validation to guarantee user requirement compliance and specification-oriented correctness. In this article, we propose a model-based approach for early validation of MCPS, focusing [...] Read more.
Medical Cyber-Physical Systems (MCPS) are context-aware, life-critical systems with patient safety as the main concern, demanding rigorous processes for validation to guarantee user requirement compliance and specification-oriented correctness. In this article, we propose a model-based approach for early validation of MCPS, focusing on promoting reusability and productivity. It enables system developers to build MCPS formal models based on a library of patient and medical device models, and simulate the MCPS to identify undesirable behaviors at design time. Our approach has been applied to three different clinical scenarios to evaluate its reusability potential for different contexts. We have also validated our approach through an empirical evaluation with developers to assess productivity and reusability. Finally, our models have been formally verified considering functional and safety requirements and model coverage. Full article
(This article belongs to the Special Issue Cyber-Physical Systems)
Open AccessArticle A High Performance LIA-Based Interface for Battery Powered Sensing Devices
Sensors 2015, 15(10), 25260-25276; doi:10.3390/s151025260
Received: 22 June 2015 / Revised: 22 September 2015 / Accepted: 25 September 2015 / Published: 30 September 2015
Cited by 2 | PDF Full-text (1306 KB) | HTML Full-text | XML Full-text
Abstract
This paper proposes a battery-compatible electronic interface based on a general purpose lock-in amplifier (LIA) capable of recovering input signals up to the MHz range. The core is a novel ASIC fabricated in 1.8 V 0.18 µm CMOS technology, which contains a [...] Read more.
This paper proposes a battery-compatible electronic interface based on a general purpose lock-in amplifier (LIA) capable of recovering input signals up to the MHz range. The core is a novel ASIC fabricated in 1.8 V 0.18 µm CMOS technology, which contains a dual-phase analog lock-in amplifier consisting of carefully designed building blocks to allow configurability over a wide frequency range while maintaining low power consumption. It operates using square input signals. Hence, for battery-operated microcontrolled systems, where square reference and exciting signals can be generated by the embedded microcontroller, the system benefits from intrinsic advantages such as simplicity, versatility and reduction in power and size. Experimental results confirm the signal recovery capability with signal-to-noise power ratios down to −39 dB with relative errors below 0.07% up to 1 MHz. Furthermore, the system has been successfully tested measuring the response of a microcantilever-based resonant sensor, achieving similar results with better power-bandwidth trade-off compared to other LIAs based on commercial off-the-shelf (COTS) components and commercial LIA equipment. Full article
(This article belongs to the Special Issue Cyber-Physical Systems)
Open AccessArticle Self-Adaptive Strategy Based on Fuzzy Control Systems for Improving Performance in Wireless Sensors Networks
Sensors 2015, 15(9), 24125-24142; doi:10.3390/s150924125
Received: 30 June 2015 / Revised: 31 August 2015 / Accepted: 14 September 2015 / Published: 18 September 2015
Cited by 1 | PDF Full-text (2003 KB) | HTML Full-text | XML Full-text
Abstract
The solutions to cope with new challenges that societies have to face nowadays involve providing smarter daily systems. To achieve this, technology has to evolve and leverage physical systems automatic interactions, with less human intervention. Technological paradigms like Internet of Things (IoT) [...] Read more.
The solutions to cope with new challenges that societies have to face nowadays involve providing smarter daily systems. To achieve this, technology has to evolve and leverage physical systems automatic interactions, with less human intervention. Technological paradigms like Internet of Things (IoT) and Cyber-Physical Systems (CPS) are providing reference models, architectures, approaches and tools that are to support cross-domain solutions. Thus, CPS based solutions will be applied in different application domains like e-Health, Smart Grid, Smart Transportation and so on, to assure the expected response from a complex system that relies on the smooth interaction and cooperation of diverse networked physical systems. The Wireless Sensors Networks (WSN) are a well-known wireless technology that are part of large CPS. The WSN aims at monitoring a physical system, object, (e.g., the environmental condition of a cargo container), and relaying data to the targeted processing element. The WSN communication reliability, as well as a restrained energy consumption, are expected features in a WSN. This paper shows the results obtained in a real WSN deployment, based on SunSPOT nodes, which carries out a fuzzy based control strategy to improve energy consumption while keeping communication reliability and computational resources usage among boundaries. Full article
(This article belongs to the Special Issue Cyber-Physical Systems)
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Open AccessArticle Workload Model Based Dynamic Adaptation of Social Internet of Vehicles
Sensors 2015, 15(9), 23262-23285; doi:10.3390/s150923262
Received: 25 February 2015 / Revised: 31 August 2015 / Accepted: 4 September 2015 / Published: 15 September 2015
Cited by 3 | PDF Full-text (2283 KB) | HTML Full-text | XML Full-text
Abstract
Social Internet of Things (SIoT) has gained much interest among different research groups in recent times. As a key member of a smart city, the vehicular domain of SIoT (SIoV) is also undergoing steep development. In the SIoV, vehicles work as sensor-hub [...] Read more.
Social Internet of Things (SIoT) has gained much interest among different research groups in recent times. As a key member of a smart city, the vehicular domain of SIoT (SIoV) is also undergoing steep development. In the SIoV, vehicles work as sensor-hub to capture surrounding information using the in-vehicle and Smartphone sensors and later publish them for the consumers. A cloud centric cyber-physical system better describes the SIoV model where physical sensing-actuation process affects the cloud based service sharing or computation in a feedback loop or vice versa. The cyber based social relationship abstraction enables distributed, easily navigable and scalable peer-to-peer communication among the SIoV subsystems. These cyber-physical interactions involve a huge amount of data and it is difficult to form a real instance of the system to test the feasibility of SIoV applications. In this paper, we propose an analytical model to measure the workloads of various subsystems involved in the SIoV process. We present the basic model which is further extended to incorporate complex scenarios. We provide extensive simulation results for different parameter settings of the SIoV system. The findings of the analyses are further used to design example adaptation strategies for the SIoV subsystems which would foster deployment of intelligent transport systems. Full article
(This article belongs to the Special Issue Cyber-Physical Systems)
Open AccessArticle Optimization and Control of Cyber-Physical Vehicle Systems
Sensors 2015, 15(9), 23020-23049; doi:10.3390/s150923020
Received: 2 July 2015 / Revised: 10 August 2015 / Accepted: 27 August 2015 / Published: 11 September 2015
Cited by 1 | PDF Full-text (609 KB) | HTML Full-text | XML Full-text
Abstract
A cyber-physical system (CPS) is composed of tightly-integrated computation, communication and physical elements. Medical devices, buildings, mobile devices, robots, transportation and energy systems can benefit from CPS co-design and optimization techniques. Cyber-physical vehicle systems (CPVSs) are rapidly advancing due to progress in [...] Read more.
A cyber-physical system (CPS) is composed of tightly-integrated computation, communication and physical elements. Medical devices, buildings, mobile devices, robots, transportation and energy systems can benefit from CPS co-design and optimization techniques. Cyber-physical vehicle systems (CPVSs) are rapidly advancing due to progress in real-time computing, control and artificial intelligence. Multidisciplinary or multi-objective design optimization maximizes CPS efficiency, capability and safety, while online regulation enables the vehicle to be responsive to disturbances, modeling errors and uncertainties. CPVS optimization occurs at design-time and at run-time. This paper surveys the run-time cooperative optimization or co-optimization of cyber and physical systems, which have historically been considered separately. A run-time CPVS is also cooperatively regulated or co-regulated when cyber and physical resources are utilized in a manner that is responsive to both cyber and physical system requirements. This paper surveys research that considers both cyber and physical resources in co-optimization and co-regulation schemes with applications to mobile robotic and vehicle systems. Time-varying sampling patterns, sensor scheduling, anytime control, feedback scheduling, task and motion planning and resource sharing are examined. Full article
(This article belongs to the Special Issue Cyber-Physical Systems)
Open AccessArticle Model-Based Design of Tree WSNs for Decentralized Detection
Sensors 2015, 15(8), 20608-20647; doi:10.3390/s150820608
Received: 1 January 2015 / Accepted: 3 August 2015 / Published: 20 August 2015
PDF Full-text (1958 KB) | HTML Full-text | XML Full-text
Abstract
The classical decentralized detection problem of finding the optimal decision rules at the sensor and fusion center, as well as variants that introduce physical channel impairments have been studied extensively in the literature. The deployment of WSNs in decentralized detection applications brings [...] Read more.
The classical decentralized detection problem of finding the optimal decision rules at the sensor and fusion center, as well as variants that introduce physical channel impairments have been studied extensively in the literature. The deployment of WSNs in decentralized detection applications brings new challenges to the field. Protocols for different communication layers have to be co-designed to optimize the detection performance. In this paper, we consider the communication network design problem for a tree WSN. We pursue a system-level approach where a complete model for the system is developed that captures the interactions between different layers, as well as different sensor quality measures. For network optimization, we propose a hierarchical optimization algorithm that lends itself to the tree structure, requiring only local network information. The proposed design approach shows superior performance over several contentionless and contention-based network design approaches. Full article
(This article belongs to the Special Issue Cyber-Physical Systems)
Open AccessArticle Nano-Enriched and Autonomous Sensing Framework for Dissolved Oxygen
Sensors 2015, 15(8), 20193-20203; doi:10.3390/s150820193
Received: 18 June 2015 / Revised: 18 July 2015 / Accepted: 22 July 2015 / Published: 14 August 2015
Cited by 1 | PDF Full-text (1440 KB) | HTML Full-text | XML Full-text
Abstract
This paper investigates a nano-enhanced wireless sensing framework for dissolved oxygen (DO). The system integrates a nanosensor that employs cerium oxide (ceria) nanoparticles to monitor the concentration of DO in aqueous media via optical fluorescence quenching. We propose a comprehensive sensing framework [...] Read more.
This paper investigates a nano-enhanced wireless sensing framework for dissolved oxygen (DO). The system integrates a nanosensor that employs cerium oxide (ceria) nanoparticles to monitor the concentration of DO in aqueous media via optical fluorescence quenching. We propose a comprehensive sensing framework with the nanosensor equipped with a digital interface where the sensor output is digitized and dispatched wirelessly to a trustworthy data collection and analysis framework for consolidation and information extraction. The proposed system collects and processes the sensor readings to provide clear indications about the current or the anticipated dissolved oxygen levels in the aqueous media. Full article
(This article belongs to the Special Issue Cyber-Physical Systems)
Open AccessArticle CoAP-Based Mobility Management for the Internet of Things
Sensors 2015, 15(7), 16060-16082; doi:10.3390/s150716060
Received: 12 May 2015 / Revised: 19 June 2015 / Accepted: 29 June 2015 / Published: 3 July 2015
PDF Full-text (1153 KB) | HTML Full-text | XML Full-text
Abstract
Most of the current mobility management protocols such as Mobile IP and its variants standardized by the IETF may not be suitable to support mobility management for Web-based applications in an Internet of Things (IoT) environment. This is because the sensor nodes [...] Read more.
Most of the current mobility management protocols such as Mobile IP and its variants standardized by the IETF may not be suitable to support mobility management for Web-based applications in an Internet of Things (IoT) environment. This is because the sensor nodes have limited power capacity, usually operating in sleep/wakeup mode in a constrained wireless network. In addition, sometimes the sensor nodes may act as the server using the CoAP protocol in an IoT environment. This makes it difficult for Web clients to properly retrieve the sensing data from the mobile sensor nodes in an IoT environment. In this article, we propose a mobility management protocol, named CoMP, which can effectively retrieve the sensing data of sensor nodes while they are moving. The salient feature of CoMP is that it makes use of the IETF CoAP protocol for mobility management, instead of using Mobile IP. Thus CoMP can eliminates the additional signaling overhead of Mobile IP, provides reliable mobility management, and prevents the packet loss. CoMP employs a separate location management server to keep track of the location of the mobile sensor nodes. In order to prevent the loss of important sensing data during movement, a holding mode of operation has been introduced. All the signaling procedures including discovery, registration, binding and holding have been designed by extending the IETF CoAP protocol. The numerical analysis and simulation have been done for performance evaluation in terms of the handover latency and packet loss. The results show that the proposed CoMP is superior to previous mobility management protocols, i.e., Mobile IPv4/v6 (MIPv4/v6), Hierarchical Mobile IPv4/v6 (HMIPv4/v6), in terms of the handover latency and packet loss. Full article
(This article belongs to the Special Issue Cyber-Physical Systems)
Open AccessArticle On-Board Event-Based State Estimation for Trajectory Approaching and Tracking of a Vehicle
Sensors 2015, 15(6), 14569-14590; doi:10.3390/s150614569
Received: 1 April 2015 / Revised: 9 June 2015 / Accepted: 17 June 2015 / Published: 19 June 2015
Cited by 1 | PDF Full-text (648 KB) | HTML Full-text | XML Full-text
Abstract
For the problem of pose estimation of an autonomous vehicle using networked external sensors, the processing capacity and battery consumption of these sensors, as well as the communication channel load should be optimized. Here, we report an event-based state estimator (EBSE) consisting [...] Read more.
For the problem of pose estimation of an autonomous vehicle using networked external sensors, the processing capacity and battery consumption of these sensors, as well as the communication channel load should be optimized. Here, we report an event-based state estimator (EBSE) consisting of an unscented Kalman filter that uses a triggering mechanism based on the estimation error covariance matrix to request measurements from the external sensors. This EBSE generates the events of the estimator module on-board the vehicle and, thus, allows the sensors to remain in stand-by mode until an event is generated. The proposed algorithm requests a measurement every time the estimation distance root mean squared error (DRMS) value, obtained from the estimator’s covariance matrix, exceeds a threshold value. This triggering threshold can be adapted to the vehicle’s working conditions rendering the estimator even more efficient. An example of the use of the proposed EBSE is given, where the autonomous vehicle must approach and follow a reference trajectory. By making the threshold a function of the distance to the reference location, the estimator can halve the use of the sensors with a negligible deterioration in the performance of the approaching maneuver. Full article
(This article belongs to the Special Issue Cyber-Physical Systems)
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Open AccessArticle Guaranteeing Isochronous Control of Networked Motion Control Systems Using Phase Offset Adjustment
Sensors 2015, 15(6), 13945-13965; doi:10.3390/s150613945
Received: 22 April 2015 / Revised: 4 June 2015 / Accepted: 5 June 2015 / Published: 12 June 2015
Cited by 2 | PDF Full-text (5834 KB) | HTML Full-text | XML Full-text
Abstract
Guaranteeing isochronous transfer of control commands is an essential function for networked motion control systems. The adoption of real-time Ethernet (RTE) technologies may be profitable in guaranteeing deterministic transfer of control messages. However, unpredictable behavior of software in the motion controller often [...] Read more.
Guaranteeing isochronous transfer of control commands is an essential function for networked motion control systems. The adoption of real-time Ethernet (RTE) technologies may be profitable in guaranteeing deterministic transfer of control messages. However, unpredictable behavior of software in the motion controller often results in unexpectedly large deviation in control message transmission intervals, and thus leads to imprecise motion. This paper presents a simple and efficient heuristic to guarantee the end-to-end isochronous control with very small jitter. The key idea of our approach is to adjust the phase offset of control message transmission time in the motion controller by investigating the behavior of motion control task. In realizing the idea, we performed a pre-runtime analysis to determine a safe and reliable phase offset and applied the phase offset to the runtime code of motion controller by customizing an open-source based integrated development environment (IDE). We also constructed an EtherCAT-based motion control system testbed and performed extensive experiments on the testbed to verify the effectiveness of our approach. The experimental results show that our heuristic is highly effective even for low-end embedded controller implemented in open-source software components under various configurations of control period and the number of motor drives. Full article
(This article belongs to the Special Issue Cyber-Physical Systems)
Open AccessArticle Solving Energy-Aware Real-Time Tasks Scheduling Problem with Shuffled Frog Leaping Algorithm on Heterogeneous Platforms
Sensors 2015, 15(6), 13778-13804; doi:10.3390/s150613778
Received: 5 March 2015 / Revised: 21 May 2015 / Accepted: 5 June 2015 / Published: 11 June 2015
Cited by 3 | PDF Full-text (1181 KB) | HTML Full-text | XML Full-text
Abstract
Reducing energy consumption is becoming very important in order to keep battery life and lower overall operational costs for heterogeneous real-time multiprocessor systems. In this paper, we first formulate this as a combinatorial optimization problem. Then, a successful meta-heuristic, called Shuffled Frog [...] Read more.
Reducing energy consumption is becoming very important in order to keep battery life and lower overall operational costs for heterogeneous real-time multiprocessor systems. In this paper, we first formulate this as a combinatorial optimization problem. Then, a successful meta-heuristic, called Shuffled Frog Leaping Algorithm (SFLA) is proposed to reduce the energy consumption. Precocity remission and local optimal avoidance techniques are proposed to avoid the precocity and improve the solution quality. Convergence acceleration significantly reduces the search time. Experimental results show that the SFLA-based energy-aware meta-heuristic uses 30% less energy than the Ant Colony Optimization (ACO) algorithm, and 60% less energy than the Genetic Algorithm (GA) algorithm. Remarkably, the running time of the SFLA-based meta-heuristic is 20 and 200 times less than ACO and GA, respectively, for finding the optimal solution. Full article
(This article belongs to the Special Issue Cyber-Physical Systems)
Open AccessArticle Aperiodic Linear Networked Control Considering Variable Channel Delays: Application to Robots Coordination
Sensors 2015, 15(6), 12454-12473; doi:10.3390/s150612454
Received: 30 March 2015 / Accepted: 21 May 2015 / Published: 27 May 2015
Cited by 1 | PDF Full-text (9679 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
One of the main challenges in wireless cyber-physical systems is to reduce the load of the communication channel while preserving the control performance. In this way, communication resources are liberated for other applications sharing the channel bandwidth. The main contribution of this [...] Read more.
One of the main challenges in wireless cyber-physical systems is to reduce the load of the communication channel while preserving the control performance. In this way, communication resources are liberated for other applications sharing the channel bandwidth. The main contribution of this work is the design of a remote control solution based on an aperiodic and adaptive triggering mechanism considering the current network delay of multiple robotics units. Working with the actual network delay instead of the maximum one leads to abandoning this conservative assumption, since the triggering condition is fixed depending on the current state of the network. This way, the controller manages the usage of the wireless channel in order to reduce the channel delay and to improve the availability of the communication resources. The communication standard under study is the widespread IEEE 802.11g, whose channel delay is clearly uncertain. First, the adaptive self-triggered control is validated through the TrueTime simulation tool configured for the mentioned WiFi standard. Implementation results applying the aperiodic linear control laws on four P3-DX robots are also included. Both of them demonstrate the advantage of this solution in terms of network accessing and control performance with respect to periodic and non-adaptive self-triggered alternatives. Full article
(This article belongs to the Special Issue Cyber-Physical Systems)
Open AccessArticle Collaborative Localization and Location Verification in WSNs
Sensors 2015, 15(5), 10631-10649; doi:10.3390/s150510631
Received: 5 February 2015 / Revised: 21 April 2015 / Accepted: 24 April 2015 / Published: 6 May 2015
Cited by 3 | PDF Full-text (1038 KB) | HTML Full-text | XML Full-text
Abstract
Localization is one of the most important technologies in wireless sensor networks. A lightweight distributed node localization scheme is proposed by considering the limited computational capacity of WSNs. The proposed scheme introduces the virtual force model to determine the location by incremental [...] Read more.
Localization is one of the most important technologies in wireless sensor networks. A lightweight distributed node localization scheme is proposed by considering the limited computational capacity of WSNs. The proposed scheme introduces the virtual force model to determine the location by incremental refinement. Aiming at solving the drifting problem and malicious anchor problem, a location verification algorithm based on the virtual force mode is presented. In addition, an anchor promotion algorithm using the localization reliability model is proposed to re-locate the drifted nodes. Extended simulation experiments indicate that the localization algorithm has relatively high precision and the location verification algorithm has relatively high accuracy. The communication overhead of these algorithms is relative low, and the whole set of reliable localization methods is practical as well as comprehensive. Full article
(This article belongs to the Special Issue Cyber-Physical Systems)
Open AccessArticle Analyzing SystemC Designs: SystemC Analysis Approaches for Varying Applications
Sensors 2015, 15(5), 10399-10421; doi:10.3390/s150510399
Received: 30 December 2014 / Revised: 17 April 2015 / Accepted: 22 April 2015 / Published: 4 May 2015
Cited by 2 | PDF Full-text (280 KB) | HTML Full-text | XML Full-text
Abstract
The complexity of hardware designs is still increasing according to Moore’s law. With embedded systems being more and more intertwined and working together not only with each other, but also with their environments as cyber physical systems (CPSs), more streamlined development workflows [...] Read more.
The complexity of hardware designs is still increasing according to Moore’s law. With embedded systems being more and more intertwined and working together not only with each other, but also with their environments as cyber physical systems (CPSs), more streamlined development workflows are employed to handle the increasing complexity during a system’s design phase. SystemC is a C++ library for the design of hardware/software systems, enabling the designer to quickly prototype, e.g., a distributed CPS without having to decide about particular implementation details (such as whether to implement a feature in hardware or in software) early in the design process. Thereby, this approach reduces the initial implementation’s complexity by offering an abstract layer with which to build a working prototype. However, as SystemC is based on C++, analyzing designs becomes a difficult task due to the complex language features that are available to the designer. Several fundamentally different approaches for analyzing SystemC designs have been suggested. This work illustrates several different SystemC analysis approaches, including their specific advantages and shortcomings, allowing designers to pick the right tools to assist them with a specific problem during the design of a system using SystemC. Full article
(This article belongs to the Special Issue Cyber-Physical Systems)
Open AccessArticle Symphony: A Framework for Accurate and Holistic WSN Simulation
Sensors 2015, 15(3), 4677-4699; doi:10.3390/s150304677
Received: 5 June 2014 / Revised: 4 February 2015 / Accepted: 10 February 2015 / Published: 25 February 2015
Cited by 1 | PDF Full-text (1737 KB) | HTML Full-text | XML Full-text
Abstract
Research on wireless sensor networks has progressed rapidly over the last decade, and these technologies have been widely adopted for both industrial and domestic uses. Several operating systems have been developed, along with a multitude of network protocols for all layers of [...] Read more.
Research on wireless sensor networks has progressed rapidly over the last decade, and these technologies have been widely adopted for both industrial and domestic uses. Several operating systems have been developed, along with a multitude of network protocols for all layers of the communication stack. Industrial Wireless Sensor Network (WSN) systems must satisfy strict criteria and are typically more complex and larger in scale than domestic systems. Together with the non-deterministic behavior of network hardware in real settings, this greatly complicates the debugging and testing of WSN functionality. To facilitate the testing, validation, and debugging of large-scale WSN systems, we have developed a simulation framework that accurately reproduces the processes that occur inside real equipment, including both hardware- and software-induced delays. The core of the framework consists of a virtualized operating system and an emulated hardware platform that is integrated with the general purpose network simulator ns-3. Our framework enables the user to adjust the real code base as would be done in real deployments and also to test the boundary effects of different hardware components on the performance of distributed applications and protocols. Additionally we have developed a clock emulator with several different skew models and a component that handles sensory data feeds. The new framework should substantially shorten WSN application development cycles. Full article
(This article belongs to the Special Issue Cyber-Physical Systems)
Open AccessArticle Efficient Evaluation of Wireless Real-Time Control Networks
Sensors 2015, 15(2), 4134-4153; doi:10.3390/s150204134
Received: 31 December 2014 / Accepted: 31 January 2015 / Published: 11 February 2015
Cited by 3 | PDF Full-text (500 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we present a system simulation framework for the design and performance evaluation of complex wireless cyber-physical systems. We describe the simulator architecture and the specific developments that are required to simulate cyber-physical systems relying on multi-channel, multihop mesh networks. [...] Read more.
In this paper, we present a system simulation framework for the design and performance evaluation of complex wireless cyber-physical systems. We describe the simulator architecture and the specific developments that are required to simulate cyber-physical systems relying on multi-channel, multihop mesh networks. We introduce realistic and efficient physical layer models and a system simulation methodology, which provides statistically significant performance evaluation results with low computational complexity. The capabilities of the proposed framework are illustrated in the example of WirelessHART, a centralized, real-time, multi-hop mesh network designed for industrial control and monitor applications. Full article
(This article belongs to the Special Issue Cyber-Physical Systems)
Open AccessArticle Cyber Surveillance for Flood Disasters
Sensors 2015, 15(2), 2369-2387; doi:10.3390/s150202369
Received: 17 November 2014 / Accepted: 12 January 2015 / Published: 22 January 2015
Cited by 3 | PDF Full-text (1946 KB) | HTML Full-text | XML Full-text
Abstract
Regional heavy rainfall is usually caused by the influence of extreme weather conditions. Instant heavy rainfall often results in the flooding of rivers and the neighboring low-lying areas, which is responsible for a large number of casualties and considerable property loss. The [...] Read more.
Regional heavy rainfall is usually caused by the influence of extreme weather conditions. Instant heavy rainfall often results in the flooding of rivers and the neighboring low-lying areas, which is responsible for a large number of casualties and considerable property loss. The existing precipitation forecast systems mostly focus on the analysis and forecast of large-scale areas but do not provide precise instant automatic monitoring and alert feedback for individual river areas and sections. Therefore, in this paper, we propose an easy method to automatically monitor the flood object of a specific area, based on the currently widely used remote cyber surveillance systems and image processing methods, in order to obtain instant flooding and waterlogging event feedback. The intrusion detection mode of these surveillance systems is used in this study, wherein a flood is considered a possible invasion object. Through the detection and verification of flood objects, automatic flood risk-level monitoring of specific individual river segments, as well as the automatic urban inundation detection, has become possible. The proposed method can better meet the practical needs of disaster prevention than the method of large-area forecasting. It also has several other advantages, such as flexibility in location selection, no requirement of a standard water-level ruler, and a relatively large field of view, when compared with the traditional water-level measurements using video screens. The results can offer prompt reference for appropriate disaster warning actions in small areas, making them more accurate and effective. Full article
(This article belongs to the Special Issue Cyber-Physical Systems)

Review

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Open AccessReview Network Challenges for Cyber Physical Systems with Tiny Wireless Devices: A Case Study on Reliable Pipeline Condition Monitoring
Sensors 2015, 15(4), 7172-7205; doi:10.3390/s150407172
Received: 31 December 2014 / Revised: 5 March 2015 / Accepted: 5 March 2015 / Published: 25 March 2015
Cited by 4 | PDF Full-text (2440 KB) | HTML Full-text | XML Full-text
Abstract
The synergy of computational and physical network components leading to the Internet of Things, Data and Services has been made feasible by the use of Cyber Physical Systems (CPSs). CPS engineering promises to impact system condition monitoring for a diverse range of [...] Read more.
The synergy of computational and physical network components leading to the Internet of Things, Data and Services has been made feasible by the use of Cyber Physical Systems (CPSs). CPS engineering promises to impact system condition monitoring for a diverse range of fields from healthcare, manufacturing, and transportation to aerospace and warfare. CPS for environment monitoring applications completely transforms human-to-human, human-to-machine and machine-to-machine interactions with the use of Internet Cloud. A recent trend is to gain assistance from mergers between virtual networking and physical actuation to reliably perform all conventional and complex sensing and communication tasks. Oil and gas pipeline monitoring provides a novel example of the benefits of CPS, providing a reliable remote monitoring platform to leverage environment, strategic and economic benefits. In this paper, we evaluate the applications and technical requirements for seamlessly integrating CPS with sensor network plane from a reliability perspective and review the strategies for communicating information between remote monitoring sites and the widely deployed sensor nodes. Related challenges and issues in network architecture design and relevant protocols are also provided with classification. This is supported by a case study on implementing reliable monitoring of oil and gas pipeline installations. Network parameters like node-discovery, node-mobility, data security, link connectivity, data aggregation, information knowledge discovery and quality of service provisioning have been reviewed. Full article
(This article belongs to the Special Issue Cyber-Physical Systems)
Open AccessReview The Past, Present and Future of Cyber-Physical Systems: A Focus on Models
Sensors 2015, 15(3), 4837-4869; doi:10.3390/s150304837
Received: 31 December 2014 / Revised: 22 January 2015 / Accepted: 3 February 2015 / Published: 26 February 2015
Cited by 25 | PDF Full-text (298 KB) | HTML Full-text | XML Full-text
Abstract
This paper is about better engineering of cyber-physical systems (CPSs) through better models. Deterministic models have historically proven extremely useful and arguably form the kingpin of the industrial revolution and the digital and information technology revolutions. Key deterministic models that have proven [...] Read more.
This paper is about better engineering of cyber-physical systems (CPSs) through better models. Deterministic models have historically proven extremely useful and arguably form the kingpin of the industrial revolution and the digital and information technology revolutions. Key deterministic models that have proven successful include differential equations, synchronous digital logic and single-threaded imperative programs. Cyber-physical systems, however, combine these models in such a way that determinism is not preserved. Two projects show that deterministic CPS models with faithful physical realizations are possible and practical. The first project is PRET, which shows that the timing precision of synchronous digital logic can be practically made available at the software level of abstraction. The second project is Ptides (programming temporally-integrated distributed embedded systems), which shows that deterministic models for distributed cyber-physical systems have practical faithful realizations. These projects are existence proofs that deterministic CPS models are possible and practical. Full article
(This article belongs to the Special Issue Cyber-Physical Systems)

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