First of all, it is necessary to describe what an industrial communications network consists of. We could say that it is the sum of the means of transmission that allow the communication of the different elements that are connected to said network to information exchange. In this way, there can be a connection between the different layers that make up a generic factory, from the offices that manage the company to the machines that manufacture the product. In the upper layers (offices and first levels of the factory) large volumes of data, and hardly any control is carried out, admitting longer transmission times. At the levels closest to the interaction with the manufactured product, few volumes of data are transmitted and practically all the work is done. control, requiring less transmission time, although with determinism (It must be guaranteed that the transmission is carried out in a maximum time, which is usually called real-time control).
The figure represents the MIC pyramid (Computer Integrated Manufacturing), where the different levels of the ideal fully automated factory are established:
- Factory level (management): it is the furthest from the production processes, its elements being computers and servers. Information from lower levels arrives at this level, making it possible for company managers to make decisions, and similarly, orders are sent from the higher level to lower levels. this communication does not have to be especially robust or fast, but it must be suitable for the transmission of large amount of data. For this reason, standard Ethernet networks are often used (EthernetTCP/IP). Computer applications such as ERP (Enterprise Resource Planning), MONTH (Manufacturing Execution Systems), CAD/CAM/CAE (Computer Aided Design/Manufacturing/Engineering), Etc.
- plant level: is the level at which the different control systems and supervision. In order to carry out an adequate monitoring of the different processes, a communication is established between these systems and the supervision elements (visualization screens or HMI, SCADA, etc.). Networks are usually of the type EthernetTCP/IP.
- cell level: at this level, the orders that come from higher levels are received and are broken down into easier operations that are transferred to the lower level (transport, manufacturing, assembly, quality control...). From this level it is necessary to have a robust communication in harsh environments (interferences, extreme temperatures, dust and dirt), deterministic (ensures that the information has been transmitted in a maximum time) to be able to work in real time, and with high reliability and availability (with redundancy and/or error detection mechanisms). Hence the networks of Industrial Ethernet, based on Ethernet TCP/IP but with these new features for use in an industrial environment (Modbus TCP, EtherNet/IP, Profinet, EtherCAT, etc.).
- field level: at this level we have the elements of command and control that manage the sensors and actuators of the lower level. They are PLCs, numerical control systems, robots, control cards, etc. Between this level and the lower level there is capacity to do productive work on their own. Here we are already in control networks more than data (EtherNet/IP, Profinet, ControlNet, Profibus-FMS, etc.)
- Process or instrumentation level (sensors and actuators): is the level where the measure items (sensors) and command (actuators such as motors or valves) that interact with the product executing the orders of the control elements. Communication between these elements and higher level controllers is strictly real time (AS-i, DeviceNet, Profibus-DP, Profibus-PA, FieldBus, etc.).
We will continue talking about industrial networks in successive posts.