cascade control using siemens fb41_C - PLCS.net

tajammal · October 25th, 2010, 11:52 PM

dear friends!
i want to use output of one controller (PID siemens FB41_c)as setpoint of second controller.(cascade control?). how can i scale 1st. controller output to setpoint range of second controller.
thanks

KalleOlsen · October 26th, 2010, 10:47 AM

With LMN_HLM / LMN_LLM.

Try also to select FB41 and push the magical F1 button.

With your Step7 installation you will also find the CTRL-manual (pdf).

K

Jeff23spl · October 26th, 2010, 11:19 AM

i try to use 0-100% (0.0000 to 1.0000) as all input and output of my pid and the rescale it to engeneer units...i feel it easier this way.

I did few analog cascade to on-off reverse controling to save analog card for motorised valves....A first pid determine the output needed to get the sp asked and than another pid control output pulses to open or close the valve according to position setpoint

be aware of your scan time VS where you put the subroutine....The doc and help file about it is very good for pid controler

October 25th, 2010, 11:52 PM	#1
tajammal Member Join Date: Oct 2010 Location: Lahore Posts: 15	cascade control using siemens fb41_C dear friends! i want to use output of one controller (PID siemens FB41_c)as setpoint of second controller.(cascade control?). how can i scale 1st. controller output to setpoint range of second controller. thanks

October 26th, 2010, 11:19 AM	#3
Jeff23spl Member Join Date: Jan 2010 Location: Canada Posts: 600	i try to use 0-100% (0.0000 to 1.0000) as all input and output of my pid and the rescale it to engeneer units...i feel it easier this way. I did few analog cascade to on-off reverse controling to save analog card for motorised valves....A first pid determine the output needed to get the sp asked and than another pid control output pulses to open or close the valve according to position setpoint be aware of your scan time VS where you put the subroutine....The doc and help file about it is very good for pid controler __________________ Siemens Addict

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October 26th, 2010, 10:47 AM	#2
KalleOlsen Member Join Date: Oct 2008 Location: Middle of Norway Posts: 1,369	With LMN_HLM / LMN_LLM. Try also to select FB41 and push the magical F1 button. With your Step7 installation you will also find the CTRL-manual (pdf). K

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