Need the Experts in PIDE Loop

Hey guys,
I'm in need of some expert knowledge to assist in some RsLogix 5000 programming, FBD.
I currently have PIDE Loop 1 and PIDE Loop 2 which have the same PV but different outputs. What I am in need of is a way to only enable PIDE Loop 2 when the output of PIDE Loop 1 reaches a certain value. I can do this by the enable pin but once PIDE Loop 1 falls then PIDE Loop 2 is disabled causing the output to be unchanged.
Once PIDE Loop 2 reaches a certain value then I would need PIDE Loop 1 'ramp' down back to 0 output.

Is there any way of doing this?

Thanks in advance.

Use CV compare instructions to change the setpoints of your PIDE loops...so when your CV1 >= setpoint mov new CV2 setpoint to PIDE2, and then once CV2 >= setpoint mov 0 setpoint to PIDE1

Im not sure if this is what you mean:
You can put the PID in software manual by latching the .SWM bit in the PID instruction.
By this way you can switch your PID On and Off.

This is how I use it in some of my programs. I'm not sure if it is the same for a FBD PIDE as I can only use Ladder.

Jack

Luke,
Can you explain a bit more please?
By setpoint do you mean the SPProg pin? I need this to only occur when I'm in Auto mode. I've tried moving 0 to PIDE 1 once the flag is raised for CV2, but it is not backing down to 0.

I've also tried setting a 0 to the PV but this dropping the CVEU too quickly (from 60 to 1.88 or so).

Nightline,
Can you add a screen shot, I'm a little lost.

Again thank you guys for the help.

Ricky,
Yes,
so PIDE2 will have 0 sent to the SPProg2 until CVEU1 from PIDE1 hits your target, then move whatever target you want PIDE2 to hit into SPProg2. Once PIDE2 hits target you can the n move 0 into SPProg1 allowing it to ramp back down. Keep in mind that PIDE2 will now also ramp back to 0 unless you don't want it to, in which case you have to create a latch and figure out what condition you want it to ramp back down.

rickyb said:

Luke,
Nightline,
Can you add a screen shot, I'm a little lost.

Again thank you guys for the help.

Click to expand...

As described before: I'm not sure if this is what you mean.
But I was talking about a PID controller as I have no rights for FBD programming, assuming the bits inside are the same.
Well this is isn't, the .SWM bit from the PID instruction is a ProgManualReq in a PIDE block.
So you can switch the PIDE on and off by the bits: ProgManualReq and ProgAutoReq.

Hope this helps.

Jack

No.
#1, Don't use "Enable" to toggle the PIDE on and off. There is almost no reason EVER to use the block enables for FBD elements, especially complex instructions like PIDE.

Make sure the PIDE is set for "PIDE_Data.ProgProgReq" (Just set the bit in the PIDE to 1).
Now, to enable the PIDE, set PIDE_Data.ProgAutoReq" to true. That will enable the PIDE to run in auto, controlling it's output. To disable it, set "PIDE_Data.ProgAutoReq" to False, then the PIDE will use the "PIDE_Data.CVProg" field to set the CV to whatever is set there.

Thank you everyone for the responses.
The 'ProgAutoReq' and 'ProgManualReg' pins are already in use since the PLC is connected to my DCS system and the operator can put the system in Manual mode if needed and enter his 'CVProg' to open or close the valve. The issue is when the loop is in Auto to reach the scenario that I need.

I'm not able to switch between auto and manual since the end-user will notice this and not be very happy that the system is switching even though its controlled.

Setting ProgAutoReq to 0 is the way disable PID control, without putting it in manual.