在工业自动化领域，选择合适的系统架构对于效率、成本和未来保障来说至关重要。 如果在 PLC 与驱动器、传感器、阀岛等自动化部件之间实现智能通信，不但能大幅降低总成本，还可为系统的灵活性和可扩展性提供有力保障。 如今，用户有大量设计方案可以选择：从离散接线到具有远程 I/O 的现场总线系统，再到集中式和分布式气动连接，不一而足。 在本博文中，我们着重从成本和灵活性出发，介绍不同架构方式的应用领域及优缺点。
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With discrete wiring, each individual component, such as sensors and actuators, is connected directly to the central control unit in the control cabinet. Each input and output requires its own line. Although this eliminates the need for expensive and complex communication protocols and bus nodes, the architecture quickly reaches its limits. And as the size increases, cabling costs go up and more space is needed in the control cabinet. Once it gets extended, the system quickly becomes extremely complex and error-prone. However, this system is sufficient for small machines or systems with manageable inputs and outputs, as long as costs and space requirements are kept within limits.
Fieldbus systems are digital networks that connect several devices to the control unit via a single communication line. Examples are ProfiNET, EtherNet/IP or EtherCAT®. These are relevant for medium to large systems with a large number of inputs and outputs. This is because a fieldbus significantly increases the flexibility and scalability of a system; fewer cables are required, as a single data cable now reduces the number of discrete connections. New devices can be easily integrated into the network and different components can communicate through the same bus. Diagnostics are also simplified, as malfunctions can now be identified more easily.
At the same time, the necessary fieldbus nodes are very cost-intensive and compatibility becomes an important issue, since not every device can communicate with every fieldbus. The architecture is dependent on the fieldbus protocol used in the PLC.
Remote IO relocates IO modules with protection class IP65 and higher to remote locations close to sensors and actuators. These modules communicate with the central controller through fieldbus systems. Remote I/O is essential for large and extensive systems if the modules are to be placed outside the control cabinet and close to the components. The wiring work is minimised even further, the data rates increased and the control cabinet capacity significantly reduced. Placing the machine in the field also makes it much easier and cheaper to scale and simplifies servicing, as faults can be diagnosed and rectified directly on site.
The use of remote I/O has become an integral part of modern automation architecture and represents a major benefit for automation. However, this technology comes with the highest initial price tag. The system becomes much more dependent on a stable network connection and requires a great deal of expertise in planning and integration.
Integrating valve terminals and pneumatic components into an automation system offers great potential. Yet,it can also pose a risk of oversizing as tubing tends to be long and complex, while the need for more interfaces pushes up costs. But it is also possible to create a decentralised or hybrid (modular and decentralised) connection by using the right components and a communication language that is as uniform as possible. This reduces the number of bus nodes and IP addresses and simplifies diagnostics.