Siemens Module B3 ユーザーズマニュアル

 

 

 

 

 

 

 

   

 

 

 

 

T I A  Training Document 

Page 25 of 64 

  Module 

2.7.3.3  PI Controllers 
 

In practice, the PI controller is a controller type that is used very often.  It consists of the parallel 

connection of a P-controller and an I-controller. When laid out correctly, it combines the advantages 

of both controller types (stable and fast, no lasting system deviation), so that their disadvantages are 

compensated for at the same time.    

 

 

 

 

 

 

 

 

Block Diagram 

 

 

 

 

 

 

 

 

The trend is indicated with the proportional coefficient Kp and the reset time Tn. Based on the 

proportional component, the controller output responds immediately to each system deviation e, 

while the integral component has an effect only in the course of time.  Tn represents the time that 

passes until the I-component generates the same margin of the manipulated variable as it is 

generated immediately because of the P-component (Kp). As for the I-controller, the reset time Tn 

has to be reduced if you want to increase the integral component. 

Depending on the Kp and Tn dimensioning, the overshoot of the controlled variable can be reduced 

at the expense of control system dynamics. 

Applications for the PI controller: fast control loops that don’t permit lasting system deviations. 

Examples: pressure, temperature, ratio control.  

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

B3 

Issued: 02/2008                                                                                                                                     Control Engineering with STEP 7