20-10-2012, 02:11 PM
CONTROL SYSTEM NOTES
13300541-Control-System-Notes-by-HPK-Kumar.pdf (Size: 8.11 MB / Downloads: 427)
Definitions:
1. Controlled Variable:
It is the quantity or condition that is measured & controlled.
2. Controller:
Controller means measuring the value of the controlled variable of the system & applying the
manipulated variable to the system to correct or to limit the deviation of the measured value to the
desired value.
3. Plant:
A plant is a piece of equipment, which is a set of machine parts functioning together. The
purpose of which is to perform a particular operation. Example: Furnace, Space craft etc.,
4. System:
A system is a combination of components that works together & performs certain objective.
5. Disturbance:
A disturbance is a signal that tends to affect the value of the output of a system. If a disturbance
is created inside the system, it is called internal. While an external disturbance is generated outside the
system.
6. Feedback Control:
It is an operation that, in the presence of disturbance tends to reduce the difference between the
output of a system & some reference input.
7. Servo Mechanism:
A servo mechanism is a feedback controlled system in which the output is some mechanical
position, velocity or acceleration.
8. Open loop System:
In an Open loop System, the control action is independent of the desired output. OR
When the output quantity of the control system is not fed back to the input quantity, the control
system is called an Open loop System.
9. Closed loop System:
In the Closed loop Control System the control action is dependent on the desired output, where
the output quantity is considerably controlled by sending a command signal to input quantity.
2 Introduction to Control System
By: Sheshadri.G.S.
HPK Kumar
Feed Back:
Normally, the feed back signal has opposite polarity to the input signal. This is called negative
feed back. The advantage is the resultant signal obtained from the comparator being difference of the
two signals is of smaller magnitude. It can be handled easily by the control system. The resulting signal
is called Actuating Signal This signal has zero value when the desired output is obtained. In that
condition, control system will not operate.