Dear Experts,
In Cascade control loop, Is there any possibility to achieve the following functionality using Delta V PID controller?
Bypass secondary loop (Secondary PID Controller) in cascade control mode system and Primary (Primary PID) sends command directly to final control element as it passes set point to Secondary loop while working normally.
Thanks,
Mani
Why do you need to do this?
Anyway.. The bypass function of the PID function block of the slave controller could well be used, this simply passes the SP to output without any PID action. You need to set the bypass enable flag in the Control_opts parameter and then set the bypass parameter to true.
Hope this helps,
Regards,
Neil.
PID_Slave/CAS_IN=PID_Master/OUT
PID_Slave/TRK_IN_D=1 ---> For "Bypass" / =0 ---> For Cascade Control
PID_Slave/TRK_VAL=PID_Master/OUT ---> Check Scales
I think Roman has got it close, but what about bumpless switching of modes? Setting slave to cas must be accompanied by setting tracking to true (which will knock it out of cas, sending master into iman, right?). returning to single loop control, tracking is turned off, then slave mode is returned to auto. I'd be interested to see how the final out put transitions between modes.
In reply to Youssef.El-Bahtimy:
Mr Youssef, You are right.
We can prepare logic:
links:
CALC1/IN1=AO1/BKCAL_OUT
CALC1/IN2=PID_Slave/BKCAL_OUT
CALC1/IN3=PID_Slave/TRK_IN_D
PID_Master/BKCAL_IN=CALC1/OUT1
if IN3 then
OUT1:=IN1
else
OUT1:=IN2
endif;
What do You think about this?
In reply to Roman Kostuniak:
I wonder if a cascade is needed at all here. This is really a control select application. PID1 and PID2 output both feed into signal selector, and toggle control selects one or the other. Problem is, control select function block only lets you select based on min/max/median, not based on operator entry. When we have to do these types of applications, we usually use the input selector block, then write all the back calculated initialization via a calc block (yes, with .ST changes and everything to indicate the invited/limited/etc state of the back cal).
Mr Youssef, You are right. We can prepare logic: links: CALC1/IN1=AO1/BKCAL_OUT CALC1/IN2=PID_Slave/BKCAL_OUT CALC1/IN3=PID_Slave/TRK_IN_D PID_Master/BKCAL_IN=CALC1/OUT1 if IN3 then OUT1:=IN1 else OUT1:=IN2 endif; What do You think about this?