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Absolutely the worst control systems of all time have been written by software engineers that don’t understand control theory. The second worst control systems are designed by those who only know the PID heuristic, and can’t be bothered to model a little non-linearity from motor drives saturating.

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The biggest problem with PID control is that the integral term performs double duty as both a signal that accumulates small errors to minimize the steady state error, but also as a signal that shows deviation from the target due to unmodeled constraints.

It should be pretty obvious that you cannot overcome constraints by moving even harder in the direction of the constraint, which is what the integral term does.

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