Flexible Node Research Articles

Topological Structure and Control Strategy of E-UPFC

This article proposes a unified power flow controller with energy (E-UPFC) installed at the renewable energy grid connection node of the transmission network. Compared with other unified power flow controllers (UPFCs), the proposed E-UPFC can not only regulate the power flow on its connected transmission lines, but also suppress the power fluctuations of grid-connected nodes injected with large-scale renewable energy. At the same time, with the installation position of E-UPFC transferred from the transmission line to the node, the original stiff node can be transformed into a flexible node that can regulate the injected power flexibly. First, the PV grid-connected system with E-UPFC is introduced, and its principle of power flow regulation is detailed. In addition, the topology, mathematical modeling, and control strategies of E-UPFC are discussed. Finally, the E-UPFC is applied to the IEEE 3-generator 9-bus system with large-scale renewable energy integration in Matlab/Simulink in order to verify the correctness and feasibility of E-UPFC and its control strategies.

Uncertainty Modeling of a Chemical System with a Flexible Node by Mapping the Fault Tree into the Response Surface Method

This paper elaborates three novel contributions in the field of chemical process safety. The first contribution is the identification and classification of chemical system variabilities into seven broad categories, namely, media, equipment, component, operator, procedural, management, and external (MECOPME). The identified variabilities lead to epistemic and aleatory types of uncertainties in the probabilistic safety analysis. To deal with the uncertainties caused due to the variabilities, a concept of the flexible node is proposed, which demands a failure probability in the flexible range of a lower level to a higher level instead of a fixed static probability. Since the existing techniques are not robust enough to handle the probability range, the classical fault tree is mapped into a statistically more reliable approach of the response surface method (RSM). The unique idea of using RSM in the failure analysis is demonstrated over the fault tree of an overtemperature scenario in a semipilot scale setup for the hydrogenation process and successfully evaluated over an industrial accident of the release prevention barrier scenario. The contour and surface plots of RSM reveal more information than the traditional approach of minimal cut sets. The statistical markers of RSM are a better substitute for the improvement index for sensitivity analysis. The proposed approach deals with chemical system variabilities and the lack of knowledge of exact occurrence probabilities more effectively.

Design, Assessment and Deployment of an Efficient Golf Game Dynamics Management System Based on Flexible Wireless Technologies.

The practice of sports has been steadily evolving, taking advantage of different technological tools to improve different aspects such as individual/collective training, support in match development or enhancement of audience experience. In this work, an in-house implemented monitoring system for golf training and competition is developed, composed of a set of distributed end devices, gateways and routers, connected to a web-based platform for data analysis, extraction and visualization. Extensive wireless channel analysis has been performed, by means of deterministic 3D radio channel estimations and radio frequency measurements, to provide coverage/capacity estimations for the specific use case of golf courses. The monitoring system has been fully designed considering communication as well as energy constraints, including wireless power transfer (WPT) capabilities in order to provide flexible node deployment. System validation has been performed in a real golf course, validating end-to-end connectivity and information handling to improve overall user experience.

Trustworthy Transaction Spreading Using Node Reliability Estimation in IoT Blockchain Networks

Blockchain network architecture is a promising technology for constructing highly secure Internet of Things (IoT) networks. IoT networks typically comprise various sensors and actuators. Blockchain network technology can be applied to secure control robots in smart factories or reliable drone deliveries in smart cities. The wide spread of transactions and shared smart contracts across blockchain networks guarantees ultimate network security. A typical wired blockchain network maintains sufficient redundancy within a stable configuration. However, IoT blockchain networks exhibit unavoidable instability. The dynamic configuration changes caused by flexible node membership make it impossible to achieve the same level of redundancy as a stable network. A trustworthy transaction spreading method provides practical transaction sharing for dynamic IoT networks. We propose a Q-learning framework and a graph convergence network (GCN) to search for the proper spreading path of each transaction. The proposed Q-learning framework determines the next spreading hop using node features. The GCN determines the reliable area based on the Q-learning results. The discovered reliable area guides the proper spreading path of transactions to the destination node. In addition, the proposed trustworthy transaction spreading was implemented over an InterPlanetary File system (IPFS). The IPFS-powered experiments confirmed the practicability of the proposed transaction spreading mechanism.

Distributed Target Tracking in Sensor Networks by Consistency Algorithm and Semantic Moving Computing of Internet of Things

The target tracking algorithm of mobile wireless sensor networks involves target motion trend prediction and subsequent node guidance. This study aims to solve the problems of global consistency of node information and significant errors in forecasting fast-moving targets’ trajectories through traditional distributed tracking methods in sensor networks. Initially, the average consistency algorithm is used to average the local measurements of each node to achieve global consistency. Then, semantic moving computing of the Internet of Things calculates and analyzes the node movement to support the subsequent movement guidance of nodes and target movement prediction. Finally, the simulation experiment is carried out to evaluate the commonly used target trajectory prediction model. The simulation results show that the node movement algorithm by average consistency can effectively improve the positioning accuracy of the network for moving targets. Besides, the positioning error decreases with the increase of the sensing radius R, the number of moving nodes nm, and the total number of nodes ns deployed in a particular range in a two-dimensional (2D) space. The positioning error after node movement in 2D space is about 20%–30%R lower than that in a static state. After node movement in a three-dimensional (3D) space, the positioning error is about 40%–50%R lower than in a dormant state. When the target moves at a speed greater than 7m/s, the consistency-based moving computing algorithm’s target loss rate and tracking errors are about 0~10% and 1.5%~2% lower than the target tracking algorithm via Kalman Filter. Therefore, the algorithm reported here can precisely track the high-speed moving target. The existing research on point target tracking has problems of insufficient accuracy and robustness. The algorithm proposed here has stronger robustness, reduced data error in multi-node, and more flexible node movements, providing a reference for the subsequent research on distributed point target tracking.

Efficient Flexible M-tree Bulk Loading Using FastMap and Space-filling Curves

Many database applications currently deal with objects in a metric space. Examples of such objects include unstructured multimedia objects and points of interest (POIs) in a road network. The M-tree is a dynamic index structure that facilitates an efficient search for objects in a metric space. Studies have been conducted on the bulk loading of large datasets in an M-tree. However, because previous algorithms involve excessive distance computations and disk accesses, they perform poorly in terms of their index construction and search capability. This study proposes two efficient M-tree bulk loading algorithms. Our algorithms minimize the number of distance computations and disk accesses using FastMap and a space-filling curve, thereby significantly improving the index construction and search performance. Our second algorithm is an extension of the first, and it incorporates a partitioning clustering technique and flexible node architecture to further improve the search performance. Through the use of various synthetic and real-world datasets, the experimental results demonstrated that our algorithms improved the index construction performance by up to three orders of magnitude and the search performance by up to 20.3 times over the previous algorithm.

Responsive Four-Coordinate Iron(II) Nodes in FePd(CN)4.

Metal node design is crucial for obtaining structurally diverse coordination polymers (CPs) and metal-organic frameworks with desirable properties; however, FeII ions are exclusively six-coordinated. Herein, we present a cyanide-bridged three-dimensional (3D) CP, FePd(CN)4 , bearing four-coordinate FeII ions, which is synthesized by thermal treatment of a two-dimensional (2D) six-coordinate FeII CP, Fe(H2 O)2 Pd(CN)4 ⋅4 H2 O, to remove water molecules. Atomic-resolution transmission electron microscopy and powder X-ray and neutron diffraction measurements revealed that the FePd(CN)4 structure is composed of a two-fold interpenetrated PtS topology network, where the FeII center demonstrates an intermediate geometry between tetrahedral and square-planar coordination. This four-coordinate FeII center with the distorted geometry can act as a thermo-responsive flexible node in the PtS network.

All-optical modulation format conversion from PSK to ASK based on phase-sensitive amplification

With the development of the optics communication system and optical signal modulation technology, the amplitude-shift keying (ASK) and phase-shift keying (PSK) are both used in different optical communication sub-networks. In this paper, a novel all-optical modulation format from PSK to ASK based on phase-sensitive amplification is proposed and demonstrated. Using the nonlinear interference of the single-pump phase-sensitive amplification, the signal wavelength can be preserved while the modulation format is conversed. The proposed scheme provides the flexible intermediate node interface transformation in future optical networks.

Design and implementation of a flexible node for IoT supporting 6LoWPAN and a sensor shield for home automation application

Abstract. The Internet of Things (IoT) and Industry 4.0 is evolving and has a high demand for reliable electronics. This work contributes to the creation of user-friendly and robust applications for the IoT. The topic is the development of a radio communication system regarding the requirements for the end user and concerning a high flexibility of the application. The result is a core board featuring USB programming capability to flash the user application, USB power delivery (USB-PD) for battery charging, a fuel gauge, as well as a Microcontroller Unit (MCU), and a Radio Frequency (RF) transceiver. This core board can be combined with different sensor or actor shields to increase the flexibility and re-usability. To ensure proper functionality of all crucial design blocks they are analyzed and simulated with state of the art techniques. First, the system requirements are laid out and explained in detail. The implementation that satisfies these requirements is presented and necessary simulations are discussed, the results are presented. To complete the work, measurements of the system are shown and compared with the simulation.

Twin-Ring Optical WDM-MAN Enabling Triple-Hierarchical Reconfigurations and Quadruple-Shared Protections

ABSTRACTAn optical wavelength division multiplexing metro access network is proposed in this paper. With the design of flexible distribution node (FDN), three kinds of reconfigurable networks can be flexibly built to achieve intra- and inter-optical network unit (ONU)-direct communications. With the adoption of multiple tangent twin-ring topologies, four-level shared protections covering both feeder and distribution fibers are also supported. Moreover, the network can be smoothly expanded by adding express ONUs connected to FDNs. Thus, the network can not only achieve capacity increasing but also support full-duplex reconfigurable communication. A reconfigurable transmission algorithm is also set to avoid wavelengths conflict.

Hardware-programmable optical networks

For future multi-dimensional optical networks, vast network resources provided by space division multiplexing and wavelength division multiplexing technologies, require new network architectures to scale up current network functions. The huge switch-granularity range requires a more dynamic way to deploy network resources. In this paper, we proposed a hardware-programmable optical network which deploys network resources according to incoming traffic requests. The proposed network supports node function programmability and node architecture adaptability, which are critical for dynamic function and resources deployments. Architecture-on-Demand based node architecture adapts node architectures and also enables network function programmability by incorporating with several flexible node functions. Other enabling technologies, such as ubiquitous power monitoring and dynamic optical power management, assures the programmable optical node work properly. Based on all these technologies, we established a hardware-programmable optical network testbed. Several use cases were demonstrated successfully, such as dynamic power equalization and optical debugging. These work verified the feasibility of hardware-programmable optical network, which dynamically allocate network resources for service provision. The proposed hardware programmable optical network will lead to a better hardware utilization and provide a possible solution for the future multi-dimensional optical network.

Remote Monitoring System of an Agricultural Tillage Machine Based on an Embedded ARM Technology Wireless Sensor

To solve the problems of monitoring system topology structure and joint ductility, as well as to improve the efficiency of agricultural planting, this study presents a greenhouse-monitoring system based on the advanced RISC machine (ARM) wireless sensor network. The design schemes of the hardware and software of the network nodes are presented, and the process of a ZigBee network coordinator is elucidated. The system uses ARM to control the wireless transceiver module for data transmission and reception as well to collect data through an inter-integrated circuit bus. The working-state data of the seeding machine are transmitted to the monitoring platform through the ZigBee network, which can achieve real-time data view. Test results show that the system has the advantages of a simple structure, a flexible node, and low power consumption. The effective monitoring of the agricultural seeding machine in a wireless environment is realized. This system can quickly monitor the agricultural seeding machine while working, and the data center allows reading the data for remote viewing and analysis. This system can also effectively reduce the workload of farmers, improve the efficiency of field sowing, and promote the rapid development of modern agriculture.

Novel Optical-Node Architecture Utilizing Asymmetric-Multiport Wavelength-Selective Switches

We propose a novel and highly scalable optical-node architecture utilizing MxN asymmetric-multiport wavelength-selective switches (WSSs), within which we implement subsystem-modular optical cross-connects (OXCs) and a transponder-bank-based add/drop part. Although the proposed add/drop part has a bank-based structure, it can realize flexible routing through the routing capability of the MxN WSSs. Numerical experiments verify that the proposed node architecture offers almost the same routing performance as the equivalent fully flexible node. Moreover, the proposed configuration attains substantial hardware reductions in terms of the number of WSS components in the OXC part, as well as that of optical amplifiers in the add/drop parts.

Techno-Economic Analysis of Fixed and Flexible Node Architectures in Multiperiod Scenarios [Invited

We analyze the capital expenditures (CapEx) and operational expenditures (OpEx) related to the power consumption and footprint requirements of fixed and flexible node architectures in a multiperiod scenario and under different traffic requirements. We consider fixed architectures based on muxponders, and nonblocking and partial nonblocking flexible architectures based on electrical cross connects (EXC) of different sizes. In flexible architectures, the impact of hitless traffic regrooming on the network CapEx and OpEx is also assessed. Results show that in spite of the initial higher investment required by flexible architectures, in the long term they tend to present lower CapEx and OpEx. Moreover, hitless regrooming can assist in postponing the need for increasing the footprint requirements in partial nonblocking EXCs.

Laissez-Faire : Fully Asymmetric Backscatter Communication.

Backscatter provides dual-benefits of energy harvesting and low-power communication, making it attractive to a broad class of wireless sensors. But the design of a protocol that enables extremely power-efficient radios for harvesting-based sensors as well as high-rate data transfer for data-rich sensors presents a conundrum. In this paper, we present a new fully asymmetric backscatter communication protocol where nodes blindly transmit data as and when they sense. This model enables fully flexible node designs, from extraordinarily power-efficient backscatter radios that consume barely a few micro-watts to high-throughput radios that can stream at hundreds of Kbps while consuming a paltry tens of micro-watts. The challenge, however, lies in decoding concurrent streams at the reader, which we achieve using a novel combination of time-domain separation of interleaved signal edges, and phase-domain separation of colliding transmissions. We provide an implementation of our protocol, LF-Backscatter, and show that it can achieve an order of magnitude or more improvement in throughput, latency and power over state-of-art alternatives.

Kinodynamic Planner Dual-Tree RRT (DT-RRT) for Two-Wheeled Mobile Robots Using the Rapidly Exploring Random Tree

We propose a new trajectory generation scheme called dual-tree rapidly exploring random tree (DT-RRT), which is designed on the basis of a rapidly exploring random tree (RRT) method. The DT-RRT is suitable for high-speed navigation of a two-wheeled differential mobile robot. The proposed dual tree is composed of a workspace tree and a state tree. The workspace tree finds near sets in the target workspace without considering robot kinematics. Robot trajectories are generated by the extension of the state tree under the consideration of kinematic and dynamic constraints. The proposed scheme allows for different topological structures between the workspace tree and the state tree. Owing to the different structures between two trees, flexible node extensions can be achieved. As a result, the success rate of the node extension can be increased, while the computational cost can be saved. In order to improve the quality of the trajectory, we propose a reconnect-tree scheme that can modify the generated tree structure. The advantage of the reconnect-tree scheme is that the repropagation of the conventional RRT structure is not required. From simulations, the superior performance of DT-RRT was clarified in terms of computing time and success rate. The experimental result supported high quality of the generated trajectory with fast and smooth motion of the robot.

Experimental Implementation of an All-Optical Interferometric Drop, Add, and Extract Multiplexer for Superchannels

We present the experimental implementation of an all-optical ROADM scheme for routing of an individual subchannel within an all-optical OFDM superchannel. The different functions required of optical node were demonstrated using interferometric technique with the extraction, drop, and addition of individual subchannel in a ten subchannels optically aggregated signal. The scheme we reported enables a fully flexible node compatible with future terabit per second superchannel transmission.

Virtual Network Provisioning Over Distance-Adaptive Flexible-Grid Optical Networks [Invited

In software-defined optical networks (SDONs), network services are provided in terms of virtual optical networks (VONs). VON provisioning requires additional considerations regarding their optical characteristics and constraints compared to virtual networks offered in the electrical domain. In this paper, we present a new VON provisioning procedure that is specifically designed for distance-adaptive flexible-grid optical networks. Simulations show up to three times increase in network capacity by leveraging the combined effect of flexible node mapping and distance-adaptive modulation.

Synchronous wearable wireless body sensor network composed of autonomous textile nodes.

A novel, fully-autonomous, wearable, wireless sensor network is presented, where each flexible textile node performs cooperative synchronous acquisition and distributed event detection. Computationally efficient situational-awareness algorithms are implemented on the low-power microcontroller present on each flexible node. The detected events are wirelessly transmitted to a base station, directly, as well as forwarded by other on-body nodes. For each node, a dual-polarized textile patch antenna serves as a platform for the flexible electronic circuitry. Therefore, the system is particularly suitable for comfortable and unobtrusive integration into garments. In the meantime, polarization diversity can be exploited to improve the reliability and energy-efficiency of the wireless transmission. Extensive experiments in realistic conditions have demonstrated that this new autonomous, body-centric, textile-antenna, wireless sensor network is able to correctly detect different operating conditions of a firefighter during an intervention. By relying on four network nodes integrated into the protective garment, this functionality is implemented locally, on the body, and in real time. In addition, the received sensor data are reliably transferred to a central access point at the command post, for more detailed and more comprehensive real-time visualization. This information provides coordinators and commanders with situational awareness of the entire rescue operation. A statistical analysis of measured on-body node-to-node, as well as off-body person-to-person channels is included, confirming the reliability of the communication system.

Flexible Power Flow Algorithm for Distribution Network Including Second-Order Items

For intelligent distribution system including Distributed Generations, we take the generator and load static characteristic into account and propose a flexible power flow algorithm for distribution network including second-order items. First, this algorithm modifies the distribution network power flow equations including second-order items in order to meet the static characteristic of generator and load. Moreover, we use the fsolve function of MATLAB to solve the power flow equations. This algorithm makes full use of the characteristic of high accuracy of the distribution network flow equations including second-order items and good convergence of the fsolve function. Compared with conventional distribution power flow algorithm, it does not need to set the trend flexible node type of each one. Not only the voltage amplitude, phase information of each node and the system frequency information can be calculated, as well as the actual power of generator and loads. The result of the algorithm is more in line with the practical electric power system engineering. Improved IEEE33 node system is chosen to verify the correctness of the algorithm.