PID behavior

[Greg McKaskle]

I cannot reproduce the behavior.

The first thing I'd do is to insert a bundle node between the chart and the PID. Then grow it so you can also chart the setpoint and process variable alongside the output all against Time.

Next zero out the I and D terms and see if the behavior doesn't start making sense.

Finally, I'm confused as to why there are 32 million points on the chart. I suspect it is because there was no delay in the loop at some point. Perhaps that has something to do with it? There is no model to respond to the output, so your PID behavior should be described by the terms and the artifacts from the math.

You may also find it useful to open up examples using PID. Help>>Find Examples and search for PID. Many of those will have models to control against and UIs to look at while altering the parameters.

Note that the PID coefficients for the LV PID are in academic form, not the standard form. That sometimes causes confusion during tuning.

Greg McKaskle