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Source changed 2026-10-23 07:41:16 UTC · snapshot created 2026-10-23 07:43:19 UTC · last check 2026-10-23 11:00:15 UTC

CAD.5:2 - Problem

An accurate observation of the past is not an accurate observation of the present. Between sampling and acting, the plant has evolved under known commands and unknown disturbances. Combining the latest values from several channels can therefore create a state that never existed. A point estimate can also hide alternatives that demand different actions.

Choosing the smallest estimation error does not by itself solve the control problem. Error in a harmless direction may cost more to remove than error in a direction that exhausts an actuator margin. Conversely, a low average error can coexist with an unacceptable possible trajectory.

The design problem is to obtain enough timely information for the required action and continuation, at an acceptable sensing, communication, memory and computation cost. Neither maximum observation nor minimum memory is the goal by itself.