Siemens Module B3 ユーザーズマニュアル

 

 

 

 

 

 

 

   

 

 

 

 

T I A  Training Document 

Page 9 of 64 

  Module 

 

The disturbance variable is the variable that unintentionally influences the controlled variable, and 

moves it from the current setpoint value.  A fixed setpoint control is necessary, for example, because 

a disturbance variable exists.  For the heating system considered here, this would be the outside 

temperature, for example, or any other variable that changes the room temperature from its ideal 

value.  

The setpoint value at a point in time is the value that the controlling variable should ideally have at 

that time. It should be noted that the setpoint value can change continuously under certain 

circumstances if there is a slave value control. The measured value that the measuring device used 

would establish if the controlled variable would have exactly the setpoint value is the instantaneous 

value of the reference variable. In the example, the setpoint value would be the room temperature 

desired at that time. 

This is the point where the current measured value of the controlled variable and the instantaneous 

value of the reference variable are compared. In most cases, both variables are measured circuit 

voltages. The difference of both variables is the “control deviation“ e.  It is passed on to the 

controlling element, and evaluated there (see below).   

The controlling element is the actual center piece of a control system. It evaluates the system 

deviation -that is, the information about whether, how and to what extent the controlled variable 

deviates from the current setpoint- as input information, and derives from this the 

 which, ultimately, influences the controlled variable. The controller 

output variable would be, in the example of the heating system, the voltage for the mixer motor. 

The manner in which the controlling element determines the controller output variable from the 

system deviation is the main criterion of the control system.  Part II discusses this topic in greater 

detail.  

 

 

Preface     Fundamentals     Discontinuous Action Controller     Controller Block (S)FB41     Setting the System     Appendix 

B3 

Issued: 02/2008                                                                                                                                     Control Engineering with STEP 7