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Fieldbus Systems: Embedded Networks for Automation
Published in Richard Zurawski, Networked Embedded Systems, 2017
During the last few years, a number of industrial solutions appeared that tackled the real-time requirements, mostly on the basis of switched Ethernet. Still, as with fieldbus systems, they were tailored to specific needs. Not even the use of standard Ethernet is really a common denominator, and above the data link layer, the approaches are completely different. Some use standard TCP/UDP/IP mechanisms for transmitting data, maybe enhanced by additional software layers to support both real-time and non-real-time communication, and some use dedicated communication stacks that bypass the entire IP suite. Figure 20.30 sketches the various appearances of the protocol stack. Manifold differences are also possible on the physical layer. Some approaches foresee redundant media (VNET/IP, TCnet), PROFINET-I/O uses dedicated built-in switches to reduce the data transmission jitter [64], and EtherCAT [66] as well as SERCOS III [46] need dedicated controllers. Ethernet Powerlink uses the old shared Ethernet and places a master–slave scheduling system on top of it [67]. Common to many proposed networks is that they employ clock synchronization to support real-time applications. To this end, the recent standard IEEE 1588 [62], which originally emerged in the instrumentation area, was officially adopted also by IEC. The specific requirements in the automation domain have led to several suggestions for improvement of the standard [136, 137], and work on the next revision was already started.
Fieldbus System Fundamentals
Published in Richard Zurawski, Industrial Communication Technology Handbook, 2017
During the last years, a number of industrial solutions appeared that tackled the real-time requirements, mostly on the basis of switched Ethernet. Still, as with fieldbus systems, they were tailored to specific needs. Not even the use of standard Ethernet is really a common denominator, and above the data link layer, the approaches are completely different. Some use standard TCP/UDP/IP mechanisms for transmitting data, maybe enhanced by additional software layers to support both real-time and non-real-time communication, and some use dedicated communication stacks that bypass the entire IP suite. Figure 1.25 sketches the various appearances of the protocol stack. Manifold differences are also possible on the physical layer. Some approaches foresee redundant media (VNET/IP, TCnet), PROFINET-I/O uses dedicated built-in switches to reduce the data transmission jitter [73], and EtherCAT as well as SERCOS III need dedicated controllers [59]. Ethernet Powerlink uses the old shared Ethernet and places a master–slave scheduling system on top of it. Common to many proposed networks is that they employ clock synchronization to support real-time applications. To this end, the standard IEEE 1588 [74], which originally emerged in the instrumentation area, was officially adopted also by IEC. The specific requirements in the automation domain have led to several suggestions for improvement of the standard regarding performance or fault tolerance [75,76] that were taken into account in the subsequent revision.
Ethernet and Ethernet/IP
Published in Sunit Kumar Sen, Fieldbus and Networking in Process Automation, 2014
The main features of EtherNet/IP are as follows: (a) It offers producer-consumer services and a very efficient peer-to-peer communication between slaves. (b) It is deterministic in nature with limited real-time capability. It is time based and not cycle based. It implies that control commands should reach field stations in time. (c) Real-time delivery is based on UDP, prioritization (QoS), and IEEE 1588. (d) It is compatible with OPC Internet protocols like HTTP, SNMP, FTP, and DHCP. (e) Flexible installation options like copper, fiber, and wireless. (f) To realize real-time deterministic communication, it follows standard software/standard Ethernet architectural philosophy. (g) It has a response time of 1 ms, jitter less than 1 ms and data rate 100 Mbps. (h) Both half and full duplex operations possible. (i) UDP and TCP are respectively used for real and non-real time communication. (j) Cyclic with short update periods (controller to drive and vice versa and controller to controller) as well as long update periods (controller to output module) are supported. (k) Both unicast and multicast addressing supported. (l) It uses a CSMA/CD media access control (MAC) model that determines how networked devices share a common bus.
Performance Analysis of Reliability-Based Decoding Algorithm for Short Block Length Turbo Codes
Published in IETE Journal of Research, 2022
P. Salija, B. Yamuna, T. R. Padmanabhan, Deepak Mishra
The demand for communication with short data blocks is increasing in recent years. Real-time communication and low latency applications require communication with short block length codewords. Strong channel codes are required to ensure reliable transmission over dynamic channel conditions. The demand for communication with short block Turbo codes is increasing in applications like mobile communication, wireless sensor networks, and satellite communication. In this paper, the performance of the novel reliability-based algorithm has been analyzed for 3GPP LTE, and CCSDS Turbo codes. Simulation results show that the algorithm outperforms the conventional iterative Turbo decoder in terms of BER performance. The time complexity of the performance-enhanced reliability-based Turbo decoder shows a clear advantage as SNR increases. The performance flattening at high SNR region is completely eliminated with the proposed decoding algorithm. This is a clear advantage for applications requiring communications with short block length Turbo codes. The algorithm is an attractive solution to achieve reliable and timely transmission of short block length Turbo codes in mobile and satellite communication applications. The proposed algorithm has a coding gain of 2.45 dB at a BER of 10−3 over AWGN channel with BPSK modulation for a code rate of . The algorithm has a channel adaptive complexity and has shown nearly 82% reduction in the decoding time complexity for the rate Turbo code at 3 dB SNR. The performance analysis of the level based Turbo decoding algorithm gives an insight into an alternate decoding approach for Turbo codes.
Formation-containment control of heterogeneous linear multi-agent systems with adaptive event-triggered strategies
Published in International Journal of Systems Science, 2022
Chen Yuan, Huaicheng Yan, Yuan Wang, Yufang Chang, Xisheng Zhan
Considering the limitation of communication resources in reality, it is impractical for the whole system to maintain real-time communication. For the purpose of decreasing energy consumption on both computing and communication, the event-triggered mechanism (ETM) has been regarded as a rising control scheme for MASs. Some enlightening works on solving event-based feedback control problem of MASs include Cheng et al. (2017), Yang et al. (2016), Zhang et al. (2013) and Cheng and Ugrinovskii (2016). In these works mentioned above, the design of the controller and the triggering rule rely on the eigenvalue information of Laplace matrix. In Cheng and Li (2018) and Cheng et al. (2019), a fully distributed and scalable adaptive event-based protocol is put forward for the first time. A remarkable feature of this protocol is that the positive constant in the controller is replaced by a time-varying weight which is calculated without using any global information of the networks. Zhang et al. (2021) studied scaled consensus tracking for a class of high-order nonlinear MASs. A fully distributed consensus protocol was proposed to drive agents to achieve scaled consensus with preassigned ratios. However, those results revolved around the leaderless and leader–follower consensus problem and it is not applicable for containment control problem. To address this issue, research focusing on designing adaptive ETM for containment control has emerged (Xu et al., 2019) which relaxed the assumption of knowing the eigenvalue information of the corresponding Laplacian matrix when designing the triggering function and its controller. As we discussed before, it is of great value to study the ETM for a system with relatively complex structure. In Wang et al. (2020), for homogeneous MASs containing multiple leaders with inputs, a distributed observer-based containment control protocol with a hybrid ETM was presented. The control updates of agents occur only at their own event instants. However, continuous communication between agents are still required in that type of ETM, which is against with the purpose of saving communication resources (Ding et al., 2017).