Concept control
system
- To sense deviation
of the output from the desired value and correct it, till the desired output is
achieved
- Desired value of the
output - reference output or set point
Controllers are
the controlling element of a control loop
- element which
accepts the error in some form and decided the proper corrective action - Their function is to maintain a process variable (pressure, temperature, level..) at some desired value
Plant
- system or process through which a particular quantity
or condition is controlled. This is also called the controlled system.
Controller - control
elements are components needed to generate the appropriate control signal
applied to the plant
Feedback elements
-
components needed to identify the functional relationship between the feedback
signal and the controlled output.
Reference point
-
external signal applied to the summing point of the control system to cause the
plant to produce a specified action. This signal represents the desired value
of a controlled variable and it also called “set point.”
Controlled output
-
quantity or condition of the plant which is controlled. This signal represents
the controlled variable.
Feedback signal
-
function of the output signal. It is send to the summing point and
algebraically added to the reference input signal to obtain the actuating
signal.
Actuating signal
-
the control action of he control loop and is equal to the algebraic sum of th reference input
signal and feedback signal. This is also called the “error signal.”
Manipulated variable
- process acted upon to maintain the plant output(controlled variable) at the
desired value.
Disturbance
-
undesirable input signal that upset the value of the controlled output of the
plant.
