Do Not Model Disturbance Driven Data for Controller Tuning

A fairly common stumbling block for those new to controller tuning relates
to step 2 of the controller design and tuning recipe. Step 2 says to
"collect controller output (CO) to process variable (PV) dynamic process
data around the design level of operation." But suppose disturbance
rejection is our primary control objective? Shouldn't we then step or pulse
(or "bump") our disturbance variable to generate the dynamic process test
data we require? The short answer is, no. Tuning a feedback controller
based on the disturbance to measured process variable dynamic relationship
is a certain path to failure...

Read the rest of the article at:
http://www.controlguru.com/2006/p121006.html