Why Dead Zones and Static Friction Keep Small Errors from Disappearing
One of the most confusing closed-loop symptoms is a small error near the target that never disappears.
A valve command changes slightly, but flow does not change. A motor receives a small output, but the shaft does not move. A servo is almost at target, but remains stuck. A stage has a tiny position error, and the controller keeps correcting, but the mechanics do not respond.
The controller is computing. The output variable is changing. The device is not moving.
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