We are surrounded by errors. In control engineering errors are issue from the comparison between a target, that is required to be achieved, and what the system or device we are trying to control can actually deliver. The controller will then compute the required adjustment to ensure that targets are met by acting on the system to be controlled.
It is important to learn from error and control engineering does just that, however, beware…
In many cases we are keen to try to reduce errors as we detect them. This may not be the best course of action. Sometimes, it is better to wait a bit and see what happens before taking corrective action that could potentially be drastic.
In particular, if there is some delay between the time we observe an error and the time we can do something about it, then we do need to wait for that delay to pass. If we do not, we risk making things worse by overcompensating for error that may not be so large. This over compensation arises from the controller not seeing the effect of its action until the inherent delay has passed and wanting to make things happen now when they just cannot.