A distributed control system (DCS) is a computerized control system for a process or plant, in which autonomous controllers are distributed throughout the system, but there is a monitoring control center operator. This contrasts with non-distributed control systems that use centralized controllers; Whether discrete controllers located in a central control room or inside a central computer. The DCS concept increases reliability and reduces installation costs by locating control functions near the process plant, but allows monitoring and supervisory control of the process remotely.
The distributed control systems first emerged in large process industries high critical value for safety, and were attractive because the manufacturer DCS would provide the level of local control and central monitoring equipment as an integrated package, thus reducing the risk Of integration of the design. Today, the functionality of SCADA and DCS systems is very similar, but DCS tends to be used in large plants continuous process where reliability and security are important and the control room is not geographically remote.
A distributed control system (DCS) is a specially designed automated control system consisting of control elements geographically distributed over the plant or control area. It differs from the centralized control system in which a single controller in the central position control function handles, but each element DCS process or machine or group of machines is controlled by a dedicated controller. DCS consists of a large number of local controllers in various sections of the plant control area and are connected through a high-speed communication network.
In the DCS system control functions data acquisition and control are carried out through a number of controllers DCS are microprocessor-based distributed functionally and geographically on the ground and are located near the area units where functions are performed Control or data collection as shown in the previous figure. These controllers can communicate with each other and also with other controllers such as monitoring terminals, operator terminals, historians, etc.
The distributed individual controllers are connected to field devices such as sensors and actuators. These controllers ensure the exchange of collected data to other hierarchical controllers through different field buses. Different fieldbus or standard communication protocols are used to establish communication between controllers. Some of them include Profibus, HART, arc network, Modbus, etc.
DCS is best suited for large-scale processing or manufacturing plants where a large number of continuous control loops must be controlled and controlled. The main advantage of splitting control tasks for distributed controllers is that if any part of DCS fails, the plant can continue to operate regardless of the failed section.