The controller in a closed loop system primarily does what?

In a closed-loop system, the controller plays a crucial role in maintaining desired output levels by continuously comparing the system's actual output with the desired reference input. This comparison is essential as it allows the controller to determine whether any adjustments need to be made to the system in order to minimize the difference, or error, between the output and input.

When the controller identifies a discrepancy, it calculates the necessary corrective actions and sends signals to the actuators or other components of the system to adjust the process. This feedback mechanism is what enables the system to self-regulate and maintain stability, thus ensuring that the output remains within set limits despite variations or disturbances.

The other options do not accurately reflect the primary function of the controller in this context. While output registration and alarm generation may be elements of a control system, they are not the fundamental purpose of the controller. The distinct focus of a controller in a closed-loop system is to compare and adjust based on error metrics, which underscores its critical role in maintaining the desired performance of the system.