PID settings S7-313

[immelmann]

Hello!
I am doing a project with a servo based winder with a speed regulation. Since i am a newbie at Siemens S7 i ask your guys how the CONT_C PID block is configured. My problem is to get the PID to fast enough without being unstable. With other PLC brands i am used to set the I, D as constants togheter with time but the Siemens has only time values for the I and D part. Little confusing.

 

[kamenges]

This is a very basic, general answer because I don't know what you know (or don't know as the case may be). When adjusting integral and derivative times, larger values of integral time will yield slower integral response. Larger values of derivative time will yield larger derivative response.

However, if the winder software is designed carefully you won't need much PID correction. Most of the drive command should come from the known state of the winding roll and the current machine speed. This maked PID tuning much easier.

Finally, if this is a loadcell system you will not want to use any derivative correction unless you have a very stretchy web. If you have a very stiff web derivative contribution can be especially problematic. If this is a dancer system then you may need some derivative.

Keith

 

[immelmann]

It is a loadcell system and the target tension is around 200 N. The start diameter is 90 mm and around 700 at the end. I ramp down the base speed by a radius calculation and the PID value can vary the speed between 0 - 100 %.

The material i wind up will elongate at increased tension.