Set Point

Somewhere in the system resides the goal for the control system. This goal is the set point and is analogous to the set temperature for a thermostat. In the bomb analogy, the set point is the target's position. The controller observes the target, while continuously comparing its momentary representation with the internal set point of the target's coordinates. Seen from the controller, the loop begins with the controller's action that feeds back to create the controller's perception of what it just did. In a primitive control system no representation of the controlled system may exist distinct from the controlled system itself, as feedback flows directly from what's controlled back to the controller. When the controller's action on the system does not differ from the system's feedback to the controller, we have a harmonic oscillator.

Controllers respond to minimize the difference between what the controller observes and the set point. Analogously, a flying bee controls its temperature (Chapter 9).

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