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Reliability is extremely important for control systems of energy distribution and generation. The IEC 61850 standard specifies an open architecture and communication protocols for such applications. The standard defines an open control architecture for networked control systems composed by intelligent electronic devices, stating some requirements that must be accomplished when developing reliable controllers for such systems. In this paper, we present a systematic and formal methodology to be adopted to achieve the correct implementation of the communication requirements of this standard. The methodology consists in five steps: modeling of real-time communication requirements defined by the standard; simulation of the obtained model; formal verification of the model, improved in the previous step; translation of the global model ( simulated and verified) into the input language of the real controller; and finally, application of conformance testing technique to the computational routine implemented in the real controller. Presented research deals with the proposition of a strategy to synthesize and validate models of systems developed under IEC61850 real-time requirements ( GOOSE and SMV) through simple operational conditions cases that, once validated, can be used in performance and conformance testing of more complex systems. The proposed methodology allows designers to synthesize reliable systems under IEC61850 real-time communication requirements., info:eu-repo/semantics/publishedVersion

Recent technological advances have enabled distributed control systems to be implemented via networks. This allows feedback control loops to be closed over communication channels. This paper develops a control system with high-speed and real-time communication links. Two-degrees-of-freedom control is utilized in this servo control system, and sigma-delta modulation is employed to compress data and to transmit the signal over the transmission channels between the controller and the controlled plant. Simulation results show that the controller can compensate the possible existing noise in the transmission channels. In addition, the developed system is implemented in field-programmable gate arrays. We developed a real-time closed-loop control system that has a communication channel whose control-sampling period is 600 ns and can reduce the sampling period of the controller module to hundreds of nanoseconds.

The WorldFIP protocol is one of the profiles that constitute the European fieldbus standard EN-50170. It is particularly well suited to be used in distributed computer-controlled systems where a set of process variables must be shared among network devices. To cope with the real-time requirements of such systems, the protocol provides communication services based on the exchange of periodic and aperiodic identified variables. The periodic exchanges have the highest priority and are executed at run time according to a cyclic schedule. Therefore, the respective schedulability can be determined at pre-run-time when building the schedule table. Concerning the aperiodic exchanges, the situation is different since their priority is lower and they are bandied according to a first-come-first-served policy. In this paper, a response-time-based schedulability analysis for the real-time traffic is presented. Such analysis considers both types of traffic in an integrated way, according to their priorities. Furthermore, a fixed-priorities-based policy is also used to schedule the periodic traffic. The proposed analysis represents an improvement relative to previous work and it can be evaluated online as part of a traffic online admission control. This feature is of particular importance when a planning scheduler is used, instead of the typical offline static scheduler, to allow online changes to the set of periodic process variables.

For an in-depth analysis of the delay characteristics and to demonstrate the feasibility of a reduced architecture, a pilot implementation based on the token bus was performed in the author's laboratory. The theoretical and measurement results of this work are reported. It is shown that using the immediate response option in all situations within the intended field of application leads to greater delays. Problems such as the mapping of the application services-manufacturing message standard (MMS)-onto logical line control (LLC) services are discussed. >

Industrial wireless sensor networks (IWSNs) have the potential to contribute significantly in areas such as cable replacement, mobility, flexibility, and cost reduction. Nevertheless, the industrial environment that the IWSNs operate in is very challenging because of dust, heat, water, electromagnetic interference, and interference from other wireless devices, which make it difficult for current IWSNs to guarantee reliable real-time communication. In this paper, we present a novel method based on the segmented slot assignment, fast slot competition, and free node concept that will improve the reliability and real-time communication significantly so that more advanced applications can be enabled. The main purpose of the algorithms is to improve the retransmission efficiency for time-division-multiple-access-based multihop IWSNs by using limited shared slot resources more efficiently. More importantly, the proposed algorithms support efficient slot rescheduling caused by link or node failure. We evaluate the proposed methods by using simulations and a real implementation targeting monitoring of welder machines. Our obtained results show that the proposed method outperforms the first published and most widely used IWSN standard called WirelessHART.