abstract on automation

Implementing a modern industrial application can present a
challenging mix of requirements. For example a typical control system must
interface with signals from simple sensors and actuators, yet for
many modern applications this is merely the starting point.Most PLCs are
programmed using ladder logic, which has its origins in the wiring
diagrams used to describe the layout and connections of discrete
physical relays and timers in a control system.Advanced control features, network connectivity, device
interoperability, and enterprise data integration are all capabilities
increasingly demanded in a modern industrial application. mathematically
complex applications such as proportional-integral-derivative (PID)
loops used for temperature control involve floating-point
arithmetic. PLCs must often be
added with separate”and separately programmed hardware cards to perform these calculations.To provide these capabilities in a
PLC-based application, additional processors, network gateways or
converters, middleware software running on a separate PC, and
special software for enterprise systems must often be integrated into
the system.

Examples:
Automation of Small Hydropower Station
Control & Operation system for SHP(small hydropower station) should be simple, reliable, cheap and with minimum interference of
operating personnel. And remote operations should be performed easily.

Operation of a system involves more than simply regulating a controlled variable. There are a many processes in SHP in which it is not a variable that has to be controlled but a sequence of events.To get electricity from water, many operations and steps are involved. Series, parallel, discrete setting of states, regulation of some continuous variable over time etc are required. With the help of PLC, use of hardwired relays is minimized. A large PLC has
enough number of relays to do all the operations.If there is
any need to change the control system, only the program is to be changed and it can be done easily and is is best suited for discrete control system Where the sequence of events are programmed to form a ladder diagram.

Following are the Major Role of PLC in Automation of SHP:
1)Automatic Start Sequence
2)Automatic Shutdown (Normal, Emergency).
3)Digital Governing using PLC
4)Speed Governing
5) Position Control
6) Excitation Control with PLC
7) Protection System with PLC
8) Alarm and Annunciation using PLC

In continuous processes we may need to convert the analog signal to the acceptable value to the PLC and
then with A/D converter it is converted to digital input to processor. For precise control a PID algorithm can be implemented using a PID module.Depending on the control action, speed and accuracy of system
response, the error signal may be amplified using any or combination of proportional, integral or derivative
action they can be combined to get desired control action.

Full report dowmload:
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