ITPEC FE Subject A April 2024 Question 4

Keeping the output in line with the target value — feedback control measures the output and corrects its deviation from the target.

Feedback control is closed-loop: a sensor measures the controlled output, the controller compares it with the target value (set point), and the difference drives the correction. A thermostat that switches heating on and off to hold a room temperature is the classic example.

Answer (b)

Why not others:

• •(a) — control that follows a predetermined order of steps is sequence control, as in a washing machine program
• •(c) — acting on disturbances before they affect the output is feedforward control
• •(d) — control that never uses the output is open-loop control, the opposite of feedback

Key rule: Feedback control reacts to a measured deviation in the output, feedforward control acts on a disturbance before it reaches the output, and sequence control just follows fixed steps.

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