Manual PIDM01
MA 1311-A001 EN
22
6.1 Terms for PID Control
According to the simplified block diagram as it is often used in control engineering, a
control loop consists of the main parts
controller
and
controlled section
:
Fig. 9: Block diagram
Controller
It is the part of the control loop that takes the corrective measures for correction from the
control deviation, taking into account the dynamic properties of the controlled section.
Controlled section
This is the part of the control loop that is to be controlled by the controller.
Reference variable (set point) w
Default value at which the controlled variable is to be maintained by the control system. It
is a variable that is not influenced by the control and is supplied from the outside.
Controlled variable (actual value) x
Controlled variable is the output variable of the controlled system that is recorded for the
purpose of control and feedback for comparison. In many cases, a measuring device
(sensor) is drawn in the feedback, which records the actual value. In Fig. 9: omitted for
simplicity.
Control deviation e
Difference between reference variable and controlled variable
e = w - x
that forms the
actual input variable of the controller.
Manipulated variable y
Output variable of the control device and at the same time input variable of the system. It
transmits the controlling effect of the controller to the section.
Disturbance variable z
An externally acting variable that causes a change in the actual value of the controlled
variable and triggers a control process.