Abstract-The distributed computer systems applied in industry are usually of the real-time type. In those systems the maximal system response time has to be always well known in order to ensure the functional as well as the safety parameters of the system. However, the system response time may be subject to change as a result of system development during its life cycle. As the given system grows, the response time lengthens. So it happens that in order to satisfy the real-time constraints, the response time T RES has to be reduced after the system development. One of the factors that have an influence on the T RES time, is the automata cycle of the communication system nodes. The shorter the automata cycle is, the more frequent is the data exchange between the CPU module and the communication module of the given system node, which improves the T RES value. However, having the node's application well implemented, shortening of the automata cycle may seldom be done by the application optimization. Then, the only solution would be to temporary shorten the automata cycle by execution of some of the most crucial parts of the user application. In this paper, a method for shortening the automata cycle is described.
Dedicated fieldbuses were developed to provide temporal determinisms for industrial distributed real-time systems. In the early stages, communication systems were dedicated to a single protocol and generally supported a single service. Industrial Ethernet, which is used today, supports many concurrent services, but usually only one real-time protocol at a time. However, shop-floor communication must support a range of different traffic from messages with strict real-time requirements such as time-driven messages with process data and event-driven security messages to diagnostic messages that have more relaxed temporal requirements. Thus, it is necessary to combine different real-time protocols into one communication network. This raises many challenges, especially when the goal is to use wireless communication. There is no research work on that area and this paper attempts to fill in that gap. It is a result of some experiments that were conducted while connecting a Collaborative Robot CoBotAGV with a production station for which two real-time protocols, Profinet and OPC UA, had to be combined into one wireless network interface. The first protocol was for the exchange of processing data, while the latter integrated the vehicle with Manufacturing Execution System (MES) and Transport Management System (TMS). The paper presents the real-time capabilities of such a combination—an achievable communication cycle and jitter.
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