What does tuning a controller involve?

Tuning a controller primarily involves adjusting the parameters for desired performance. This process is crucial in control systems as it enables the adjustment of the controller's response characteristics to achieve optimal performance. By modifying settings like proportional gain, integral time, and derivative time, the system can be fine-tuned to eliminate oscillations, reduce settling time, and improve overall stability.

The tuning process ensures that the control system responds appropriately to changes in input or load without overshooting or undershooting. This is essential for maintaining a consistent and stable output in various operating conditions, which is a critical requirement in many industrial applications.

The other options touch on important aspects of control systems but do not reflect the specific focus of tuning. Changing control signals may be a method of response but does not encompass the systematic adjustment of parameters. Replacing faulty components pertains to maintenance rather than tuning, and testing system efficiency, while related to overall performance evaluation, does not directly involve the tuning process itself. Thus, adjusting the parameters is the correct focus when discussing tuning a controller.