Bias and Droop?


 

Dave Casazza

TVWBB Fan
Hi All,

Working for a data historian/controls company, I had to put my hand into tuning my electric smoker by hand. Apparently I'm to tune for quarter amplitude decay, with just P (I and D set to 0).

I'm noticing that the center of the quarter amplitude decay wave is 5 degrees lower than the setpoint set.

I assume I am seeing droop.

Will the HM bias term correct this? How best to set this term when I see this behavior?

Thanks,

Dave
 
Isn't it normal for the oscillations to be below the setpoint when using proportional-only control? The key is to get a stable oscillation to find the right P value (your determined value divide by roughly 2). Then you add your I term to shift the oscillations to center around the setpoint. Finally use the D term to prevent overshoot. The B term is probably something you can leave 0 because it is a flat number added to to the result.
 

 

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