User's Manual

Automation and Drives - SCE

T I A Training Document Page 46 of 64 Module

12. Insert organization block. (→ Insert → S7 Block → Organization block)

Click on 'Organization

block’

13. Assign OB35 as name of block.( → OB35 → OK)

Note: OB35 is a so-called 'Time interrupt OB’ and ensures a

constant cycle for calling the PID controller block SFB41.

This is absolutely necessary so that the controller can be optimized by

setting the controller parameters KP, TN and TV (for (S)FB41 Gain, TI and TD).

A cycle that under certain circumstances would fluctuate -as in the case of OB1- would

cause the controlled system to fluctuate, and in the worst case, we would have a

controlled variable that would be oscillating in an unstable way.

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

Issued: 02/2008 Control Engineering with STEP 7