centralized decentralized discrete control systems
Post on 18-Jan-2017
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Distributed Control System
What is DCS?
• Centralised
• Decentralised
Centralized• Single Master - Slave(s)
system
• All Stations depend on single central controller to sent and receive information
• No direct contact between stations
Centralized• Disadvantages :
• Reliability .
• Wiring and installation costs.
• The complexity is high for a system handling very large number of variables simultaneously.
Decentralized• Hierarchical Control
Distribution
• Central Controller >Local Controller > Stations
• Different Local Controllers might not be connected together
• Also known as Layered or Hierarchical system
Decentralized• Advantages :
• Lower implementation and upgrading cost
• More reliable, flexible
• Less complex
• Lower cost of interfacing
Distributed Control System
• Customizable Decentralized System
• Hierarchy of Controllers are connected by Communication channels
• Generally designed with redundancy to handle safety-critical processes
DCS vs PLC vs SCADA• More Expensive• Control Continues
Process
• Critical Applications
• Process Oriented
• Maintains Constant Stream of Data for control
• High Speed Machine Control
• Data Gathering Oriented
• Maintains speed by Storing values and data for use during outrages
Direct Digital Control
Digital Control => Use of Computers
Direct Digital Control - A digital computer generates control signals which directly operate the control devices
Supervisory Control - A digital computer generates control signals used as reference values for conventional analog controllers
Distributed Process Control
Distributed Process Control System
i) Central Control Station
ii) Controlling portions
• Central Control Station
- Human Machine Interface
Display, Storage, I/O Devices, Control s/w• Controlling Area
- Measurement of analog & digital signals
- Generation of output to actuators• Communication: By individual channels or
shared data highways
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