Distributed Control
System
The Next Era of Factory Automation
[ Narrendar.R.C – 12MMT0007 ]
[ G.N.Abhilash – 12MMT0026 ]
Current Issues faced in Automation
• Integration and Long time Support
• System Upgrades
• Factory Support
• Enterprise Integration
Highlights of PLC
1. Low cost
2. Easy Design
3. Well Documented
4. Well supported by Industry
5. Faster Implementation
Why Does PLC Lag Behind..?
It doesn’t support the following characteristics:
• Peer to peer
• Single Database
• Security
• Alarms
• Advanced Math Functions
• Proprietary HMI
• Open Protocols
Inherent Features of DCS
1. Peer to Peer:
This benefit is seen by reduced wiring costs between controllers and with a reduction in
engineering time based on simplified mapping.
2. Single Database:
The accuracy of the initial build and the maintenance of the system are made far easier with
the single database. Transcription errors are minimized and changing tags in control schemes
is much simpler.
3. Security:
Most PLC packages don't include Security Management in the package. It must be purchased
and configured separately.
4. Alarms:
Most PLC packages don't include Alarm Management as part of the database which will add
extra time and complexity to the project.
5. Advanced Math Functions:
PID calculations are done in the CPU of the PLC so multiple and complex calculations will
slow down the process time. Additional costs may be required to do advanced math with
add on cards.
6. Proprietary HMIs:
Many PLC vendors use their own HMI which makes interface to other devices difficult and
training more expensive.
7. Open Protocols:
Some PLC vendors use proprietary protocols at the control level which makes
communication difficult.
PLC Architecture
DCS
• A distributed control system (DCS) refers to a control system usually
of a manufacturing system, process or any kind of dynamic system, in
which the controller elements are not central in location (like the
brain) but are distributed throughout the system with each
component sub-system controlled by one or more controllers.
• The entire system of controllers is connected by networks for
communication and monitoring.
• DCS is a very broad term used in a variety of industries, to monitor
and control distributed equipment
Components of DCS
1. Introduction
2. Architecture
3. CPU
4. Analog Input Module
5. Digital Input Module
6. Analog Output Module
7. Digital Output Module
8. Communication System
9. Human Interface system (HIS)
DCS Architecture
The CPU
• Model is chosen based on software to be used.
• The main memory is ensured of high reliability
by error correction code (ECC).
• Addition of the new error detection and
protection functions.
• Other newly added functions include the
memory management unit (MMU) and write
protection which ensure data integrity, the
parity check of addresses and data, the ECC
memory, and a two wire signal self checker.
Analog I/O Module
• To input an analog voltage the
continuous voltage value must be
sampled and then converted to a
numerical value by an A/D converter.
• The data value sampled will be
somewhere between the voltage at the
start and end of the sample.
• The maximum (Vmax) and minimum
(Vmin) voltages are a function of the
control hardware. These are often
specified when purchasing hardware
Digital I/O Module
• The digital I/O module is configured by
the card unit and either the terminal
unit or connector unit.
• It inputs and outputs 16 or 32 signal
points and converts signals.
• Since the types or I/O signals are
software-set, no control switch or knob
is found on this module.
Communication Systems
• The communication cards are
used to realize the generalpurpose communication of
field control station and
subsystems via serial links, so
that the subsystem may be
controlled or monitored.
Human Interface Station
The human interface system programmed
for a project/plan is designed in such a way
that it would be easy for the operator to
understand all the operations occurred in the
plant.
HIS and Monitoring Windows
Nuclear Reactor Control Unit
SCADA Based Interface
Applications
1. Electrical power grids and electrical generation plants.
2. Environmental control systems.
3. Traffic signals.
4. Radio signals.
5. Water management systems.
6. Oil refining plants.
7. Metallurgical process plants.
8. Chemical plants.
9. Pharmaceutical manufacturing.
10.Sensor networks.
11.Dry cargo and bulk oil carrier ships
What’s Next..?