Control Systems and Feedback
Feedback makes systems behave predictably
Open-loop and closed-loop control
An open-loop system acts without measuring the output, while a closed-loop system measures output and adjusts the input to reduce error. Closed-loop control is central to thermostats, cruise control, robotics, and process automation.
Core feedback terms
A setpoint is the desired value, the measured output is the actual value, and the error is the difference between them. Controllers use this error to decide corrective action.
Common controller actions
Too much feedback can cause instability
A poorly tuned controller may oscillate or amplify disturbances instead of correcting them.
Designing a feedback loop
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Step 1: Define the variable to control.
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Step 2: Measure the output reliably.
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Step 3: Compare measured output to the setpoint.
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Step 4: Choose and tune the controller.
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Step 5: Test disturbance rejection and stability.
What is the main advantage of closed-loop control?
Closed-loop systems use feedback to reduce error.
Correct answer: It automatically corrects deviations from the target
What is the difference between the setpoint and the measured output called?
The controller acts to reduce this error.
Correct answer: error
Which controller term reacts to the rate of change of error?
Derivative action anticipates change by looking at the error slope.
Correct answer: Derivative