Distributed Control System
- distributed control system
DCS initially introduced to the public on 1975. There were two big companies in Automation Control Engineering, Yokogawa and Honeywell, those who introduced the Distributed Control System (DCS) in separate places independently. Yokogawa introduced their DCS first, the CENTUM system, and then followed by Honeywell to introduced their TDC2000 no longer after CENTUM system launching.
From that time, the technology development in Automation Control System especially in Distributed Control System (DCS) has been so rapid. Nowadays, the world recognizes the big five players in the Distributed Control System (DCS) OEM and Engineering Services, they are Emerson, Yokogawa, ABB, Honeywell and Invensys. Each OEM has their own strength and core value that may differ with the other DCS OEM.
Align with the information technology revolution, the influence of this IT advancement also impacted the DCS framework. The modern DCS now has using the the COTS system, computer, software and also using the common protocol such as the Ethernet.
The Core Function of Distributed Control System (DCS)
Some of the core function of DCS in the production operations environment such as:
1. Data acquisition from field devices
2. Data processing and management
3. Plant performance and operations monitoring, surveillance and control
4. Data storage management
DCS can be integrated with the other system such as SCADA, DMC, PI in order to expand the function, such as for the corporate reporting by using PI integration, remote area monitoring and control by using SCADA, etc.
The Core Components of Distributed Control System (DCS)
Following are the core components of Distributed Control System (DCS):
1. Operator Station
The operator station is the station that has the main function as the Human Machine Interface (HMI) between the DCS (Machine) and the Plant Operator (Human). The plant operator can interface with the DCS to monitor the plant, do some control action, bypassing parameter, inspecting the trending, etc. as the common activities that related closely to the plant daily operations. The current DCS system is using the common PC desktop (with some adjustment as per required) as the operator station.
2. Engineering Station
From hardware perspective, the engineering station typically the same with operator station, but from software perspective and privilege access the engineering station has more capability. The main function of engineer station is to provide the engineering/maintenance interface to access the DCS system to do some of the activities such as configuration changes, drawing chages, back-up and restore, software update, and some critical activities that require higher level privilege compare to operator station, such as for maintenance, engineering and administration purpose.
3. DCS Configuration Module
Contain the technical configuration data of DCS, such as the graphical setting and content, parameters setup related to control object, alarm management, critical operating parameter, etc.
4. Data Historian
The Historian has the function to store the process variables, set points and output values. The Historian also called the production database, which means the database of the DCS that contain processed data that can be stored for longer time period and can be used for the higher level purpose, such as financial reporting, surveillance performance analysis, etc.
5. Control Module
As the central of computation in the DCS. It has core functions such as running the control function (PID control, comparison control, ratio control), arithmatical operations, dynamic compensation and some other control actions.
6. I/O
This is the control module interface from/to the field devices. It handles the output of DCS action, capture the input from field devices, cover the analog and digital communication method for field device communication.
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