What are the five basic components of a closed-loop feedback control system?

A closed-loop feedback control system is composed of five fundamental elements that work together to maintain a desired output. These components are:1

• Input: The reference value or set point that represents the desired operating state of the system.1
• Process being controlled: The specific operation or physical system (such as a heater, engine, or manufacturing process) to which power is applied.1
• Output: The variable of the process that is measured and compared against the input.1
• Sensing elements: The measuring devices used to monitor the current value of the output variable.1
• Controller and actuating devices: The mechanisms that compare the measured output to the reference input and adjust the process to reduce any difference between them.1

While control theory often focuses on the mathematical modeling of these systems—such as defining the state of a plant and determining optimal control laws—these five components represent the practical, physical implementation of feedback control in automated systems.12