SESKStuff Everyone Should Know
SESK: Stuff Everyone Should Know · sesk.info/eng-feedback-closed-loop

What makes a control system closed-loop?

It measures the output and feeds it back to adjust control.

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  1. It never measures output
  2. It uses output feedback ✔
  3. It runs a fixed timer

Why: A closed-loop controller repeatedly senses the process variable and adjusts an actuator. Feedback lets it respond to disturbances and model errors that an open-loop command cannot see.

Huh, didn't know that: Feedback can improve disturbance rejection, but poor tuning can also cause oscillation or instability.

The dad joke
The controller asked for feedback and actually used it.
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References

Answer: It uses output feedback. A closed-loop controller repeatedly senses the process variable and adjusts an actuator. Feedback lets it respond to disturbances and model errors that an open-loop command cannot see.

  1. NI, The PID Controller and Theory Explained www.ni.com/en/shop/labview/pid-theory-explained.html
    PID control operates within a closed loop system, or PID loop, which is a control mechanism that reads sensors to provide constant feedback
    Checked 2026-10-10.

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