rest windup ?

Hello all,

I am an operator at a Waste to Energy plant we burn house hold garbage. We use hydraulic rams to push the garbage into the combustion chamber. The combustion chamber sits on load cells. The DCS is an Emerson Ovation control system. The process variable is the combustor weight and the output controls the speed at which the rams stroke. I am new to control design but can handle something like simple tank filling but this one has me wiped. The problems is that it takes a long time for the weight to increase or decrease when the ram stroke speed is increased or decreased. I am using a PID controller with the reset set really high to minimize windup but it?s not working. The Ovation system has a controller called PIDFF (Feed Forward) can anyone explain how it works. Or can someone tell me how to set up a control loop that will ?anticipate? the process variable? Thanks for helping an ?Operator?

A Feed Forward controller uses some prediction of what output is=20 needed that usually does most of the short term control, with the PIC=20 algorithm working in parallel to essentially correct for the errors of=20 the model. If, in this case, the output of the controller sets the=20 feed rate, and the process input is the weight, you would need some=20 mathematical model that predicts the output needed for different=20 conditions, probably based on other information than the weight, but=20 related to the rate of fuel consumption. I often tune the feed=20 forward component to do about 70% of the output, leaving the other 30%=20 for the PID control.

What other variables are available that relate to fuel consumption or=20 requirement?