In this paper, we analyze the physical and network layer error sources for distributed time synchronization of large-scale optical networks with time-varying topology, and compare the performance difference with that ...
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timesynchronization is a key issue in wireless ad hoc networks. Due to the dynamic characteristics of such networks, distributedsynchronization (DS) is preferred for its reliability and validity. However, one major ...
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timesynchronization is a key issue in wireless ad hoc networks. Due to the dynamic characteristics of such networks, distributedsynchronization (DS) is preferred for its reliability and validity. However, one major drawback of this synchronization mechanism is that nodes exchange timesynchronization messages with their neighbors, which can be very time-consuming. In order to reduce network synchronization overhead while maintaining synchronization quality, this paper presents a model-free reinforcement learning distributedsynchronization (RLDS) by evaluating the current network state and node synchronization level, adaptively deciding that the current node interacts with a certain portion of its neighbors instead of all of them for synchronization information. The simulation results indicated that during the initial network synchronization, RLDS achieves the same synchronization accuracy as the traditional DS, while reducing the total communi-cation overhead by 15%. The superiority of RLDS is more evident in the long-term maintenance of network synchronization, reducing the communication overhead by 48% during 500 rounds of synchronization. This is because the number of node neighbors in communication can be appropriately reduced, thus achieving an adaptive trade-off between ensuring timesynchronization and saving communication overhead. This study shows the latent capacity of reinforcement learning in improving the performance of traditional ad hoc networking technologies.
EtherCAT is a real-time Ethernet protocol and has been widely used in the field of motion control owing to its high speed (100 or 1000 Mbps), low processor occupancy, and good synchronization performance in slaves. Ho...
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EtherCAT is a real-time Ethernet protocol and has been widely used in the field of motion control owing to its high speed (100 or 1000 Mbps), low processor occupancy, and good synchronization performance in slaves. However, the master-slave synchronization method is blank in the EtherCAT protocol. The study proposes a novel master-slave synchronization method that relies on the stable sync0 of reference slave by adjusting the trigger moment of master interpolation period to settle packet loss caused by EtherCAT master-slave un-synchronization, adaptively and dynamically. Furthermore, the proposed method improved EtherCAT to a whole new level, indicating that the EtherCAT master no longer depended on the real-time operating system (RTOS). In addition, a synchronization predictive compensation mechanism was adopted to eliminate the compensation lag defect of existing synchronization methods. Compared with conventional studies, the synchronization method improved compensation efficiency, settled inaccurate compensation with evaluation derived from different working frequencies, and eliminated accumulative error in clock. Finally, the proposed method added almost no computation and communication load and only required eight or 16 bytes to modify the EtherCAT frame coding in the interpolation period. Experiments were carried out on machine tools to demonstrate the advantage of the proposed method in improving the synchronization performance, with an average communication jitter of only 32-71 ns.
timesynchronization is a fundamental problem in any distributed system. In particular, wireless sensor networks (WSNs) require scalable timesynchronization for implementing distributed tasks on multiple sensor nodes...
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timesynchronization is a fundamental problem in any distributed system. In particular, wireless sensor networks (WSNs) require scalable timesynchronization for implementing distributed tasks on multiple sensor nodes. We propose a temperature-compensated Kalman based distributedsynchronization protocol (TICDS) using a two-way sender-receiver synchronization scheme, to achieve high synchronization accuracy while modelling the clock skew change based on its physical characteristics. By asynchronously combining estimates from neighbours, TKDS achieves better performance than the spanning tree based protocols in a fully-distributed fashion. The synchronization performance is evaluated numerically and compared with that of other well-known synchronization protocols. (C) 2017 Elsevier B.V. All rights reserved.
time-driven and event-driven control models are two fundamental design paradigms applied in distributed control systems for synchronizing decentralized activities. This paper proposes a unified architecture for combin...
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time-driven and event-driven control models are two fundamental design paradigms applied in distributed control systems for synchronizing decentralized activities. This paper proposes a unified architecture for combining both approaches. The combination offers the best of both worlds' properties, such as the expressiveness of event-driven programming and the determinism of time-driven logic. The foundations of this symbiosis are the IEC 61499 Function Block standard providing event-driven distributed control architecture and the IEEE 1588 Precision time Protocol establishing the basis for highly-accurate timesynchronization. The proposed time-complemented event-driven distributed control model aims at improving the modularity and flexibility of automation software with satisfactory control performance. The new control model has been compared with conventional centralized and distributed control approaches analytically and by simulation. The comparison results reveal that the proposed control model is efficient and flexible. Finally, a reference example has been used to demonstrate merits of the new approach.
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