Why PID Is Hard to Tune
The frustrating part of PID tuning is not that there are three gains. It is that the same gains can behave differently on another device, another load, or another sampling period.
A thermal loop heats faster after increasing proportional gain, but starts overshooting. Integral action removes steady-state error, then makes the loop overshoot more. Filtering makes the reading smoother, but the controller reacts late. Replacing a valve, motor, or heater makes yesterday’s stable gains unusable.
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