Siemens Module B3 ユーザーズマニュアル

 

 

 

 

 

 

 

   

 

 

 

 

T I A  Training Document 

Page 22 of 64 

  Module 

 

2.7.3.1 Proportional Controllers (P-Controller) 
 

In the case of a P-controller, the controller output  y is always proportional  to the recorded system 

deviation (y ~ e). The result is that a P-controller responds to a system deviation without a delay, and 

generates a controller output only if there is a deviation e. 

The proportional pressure regulator sketched in the figure below compares the force FS of the 

setpoint spring with the force FB that pressure p2 generates on the spring-elastic metal bellows.  If 

the force is not in balance, the lever rotates around the pivot point D. The valve position 

ñ changes, and accordingly the pressure p2 to be controlled until a new power balance is 

established. The figure shows the behavior of the P-controller as a sudden system deviation occurs. 

The amplitude of the controller output step y depends on the extent of the system deviation e, and 

the amount of the proportional coefficient Kp:  To keep the system deviation low, a proportional 

factor has to be selected that is as large as possible. Increasing the factor accelerates the reaction 

of the controller;  however, a value that is too high may cause overshoot, and a considerable 

oscillatory tendency of the controller. 

 

 

 

 

 

Metal Bellows

 

 

 

 

Setpoint Spring 

 

 

 

 

 

 

 

 

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

B3 

Issued: 02/2008                                                                                                                                     Control Engineering with STEP 7