Siemens Module B3 manual Automation and Drives SCE

Automation and Drives - SCE

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
	T I A Training Document	Page 46 of 64		Module
				B3
Issued: 02/2008				Control Engineering with STEP 7