Contrologix PID software manual control

yam785

Lifetime Supporting Member
Join Date
Jul 2004
Location
pa.
Posts
153
I am using a PID instruction to control system speed reference to two drives, based on the end of line machine current load. The requirements are to:
1. Auto Mode-PID output controls speed reference based on machine load%.
2. Manual Mode-Software manual mode holds output, and allows set output to be entered.
3. Back to Auto Mode-PID output starts controlling from the set output entered.

The problem:
I have the panel set-up here in office, doing testing. In Auto, the PID controls as it should when I vary the process variable.

I can put the 'SPEED_CONTROL_PID.SWM' bit in the tag database to a '1', the PID does go into Software manual mode, and allows me to enter a value into 'SPEED_CONTROL_PID.SO' in the tag database. When I put a '0' in 'SPEED_CONTROL_PID.SWM' bit in the tag database, the PID goes back to Auto, and starts controlling from the set output entered in Software Manual Mode.

This is exactly how I need it to work. But when I try to put logic in the ladder file to access these parameters, it won't accept the tag type. I keep getting the error, 'argument does not match instructions.

Wait- what the hell? Now while trying to duplicate the problem, to allow me to explain the problem, it accepted it, and works perfect now.
pid2.JPG



Thanks for the help anyway. I hope this was at least a good discription of the problem, as I've seen the discussion going on about questions asked.



Thanks.
 
Last edited:
Hi,
I don't really understand why you are using intermediate tags such as SPEED_SELECT. If you are performing your control from some sort of HMI, you need to link .SO tag directly to a numerical data entry object. When loop is in auto, it will ignore your entry into this field. But when in manual - it will set loop output based on your input. When switching back to auto - it will pick from last entry.
 
val_99 said:
Hi,
I don't really understand why you are using intermediate tags such as SPEED_SELECT. If you are performing your control from some sort of HMI, you need to link .SO tag directly to a numerical data entry object. When loop is in auto, it will ignore your entry into this field. But when in manual - it will set loop output based on your input. When switching back to auto - it will pick from last entry.

Oooh Err !....somebody mention "bumpless transfer" !!
 

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