Siemens Module B3 ユーザーズマニュアル
Automation and Drives - SCE
T I A Training Document
Page 8 of 64
Module
2.2 Components of a Control Loop
Below, the basic terminology of control engineering is explained in detail.
First, an overview shown in the diagram below:
Measuring
Device
Device
Controlled
System
System
Final
Control
Element
Control
Element
Actuator
Controlling
Element
Element
Comparing
Element
Element
Controller
1. The Controlled Variable x
It is the actual “objective“ of the control process: the variable that is to be influenced or kept constant
is the purpose of the entire system. In our example, that would be the room temperature. The
momentary value of the controlled variable existing at a certain time is called "actual value“ at that
point in time.
2. The Feedback Variable r
In a control loop, the controlled variable is constantly checked in order to be able to respond to
unintended changes. The measured variable proportional to the controlled variable is called
feedback variable. In the example "furnace“, it would correspond to the measured circuit voltage of
the inside thermometer.
Preface Fundamentals Discontinuous Action Controller Controller Block (S)FB41 Setting the System Appendix
B3
Issued: 02/2008 Control Engineering with STEP 7