Why is DCS called a distributed control system?

Well, in my opinion, only a bus-based control system can be considered a true distributed control system – in such a system, each instrument can function as a control unit, with control functions being distributed among these instruments. As a result, even if one component of the system fails, it does not affect the overall operation. If we are talking about ordinary DCS systems, they can be considered as partial distributed control systems; their role is to integrate other subsystems. For example, there may be several small devices or units, each controlled by its own PLC, and these are brought together under a DCS for centralized control, thereby establishing connections between the various smaller systems.

Multiple control stations can be distributed across different locations; if there is only one control station, in addition to local I/O, remote I/O can also be connected to it, allowing for a distributed setup. The operation stations are mainly arranged centrally to facilitate centralized monitoring. That’s why it is also called a distributed control system, featuring centralized monitoring and decentralized control.

I’ll just stay quiet, continuing to wait patiently for in-depth and thorough discussions from everyone!

In fact, DCS (Distributed Control System) has two meanings: one is a control system with a distributed structure, and any system that possesses such a structure can be called a distributed control system； One is the products (such as certain products from Yokogawa, Zhejiang Zhongkong, and HollySys), which are an architecture used for production process control. The former is not necessarily a product from a specific company; as long as it complies with certain communication protocols, any hardware product can be connected to it. Emphasized distributed structure. Its software generally includes control software, monitoring software, and management software; these can be products from various manufacturers. Typically, such a system is an open system ； The latter is a certain product, usually a closed system; that is to say, its hardware and software are both developed by that company, and the communication protocols may also be proprietary protocols. If products from other manufacturers are to be integrated into such a system, specialized technologies are required (software via OPC, hardware via specific interfaces). Therefore, the so-called DCS (Distributed Control System) is commonly referred to in Chinese as a centralized-distributed system, which emphasizes the decentralization of control functions (to achieve risk dispersion) and centralized monitoring.

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Put simply: the control system has N loops distributed throughout the facility, but all of these loops can be monitored and controlled from the operator station display

I excerpted it from the Internet: A distributed control system evolved from computer-based supervision and control systems, direct digital control systems, and computerized multi-level control systems; it represents a relatively sophisticated control and management system for production processes. In distributed control systems, microprocessors are installed near the measuring devices and control actuators according to different regions, so as to distribute control functions as much as possible while keeping management functions relatively centralized. This decentralized control method improves the reliability of control, preventing the entire system from losing control due to computer failures. When the management level fails, the process control level (control loops) still retains its independent control capability, and the failure of individual control loops does not affect the overall system. Can it be understood in this way: 1. The distribution and the extent of that distribution are relative to the existing technical approaches (computerized supervision and control systems, direct digital control systems, and computer-based multi-level control systems); even though the current distribution is not as ideal as before. 2. The distribution is reflected in the fact that control functions are allocated to different operation stations and control stations; even if an operation station fails, the control functions remain in their original effective state. 3. The distribution of various card components, that is, the distribution of the measurement circuits and control circuits.