habbalmg

I'm using the FB41 for a PID temperature control application where thePV istemperature (0-100Deg) andthe manipulated variableis a centrifugal fanVSD speed (0 - 100%).

If the initial temperature is 60 Deg and the set-point is 50 Deg, the PID block is providing LMN = 100% all the time until PV reaches 50 Deg. Then when PVgoes below 50 Deg, LMN almost radically switches to 0%.

The PID block is only changing LMN when PV is reaching the set-point value, it is working like a simple ON/OFF: LMN = 100% when PV above SP and LMN = 0% when PV below SP.

1) Isn't there a way to make the PID anticipate what it should do and start reducing LMN (and hence VSD speed) before it reaches the SP value? This would eliminate overshoot and undershoot.

2) Isn't there a way to make the PID transitions smooth around the SP value? This would eliminate shock values to be forced on the system (LMN = 0%,100%) and operation would be smooth with no radical environment changes.

My current gain is5.0, Ti = 500ms and Td=100ms.

Your soonest feedback is appreciated.