What type of control system maintains desired process variables by making continuous adjustments?

The correct choice for this question is closed loop control, which is designed to maintain desired process variables by continuously adjusting the system based on feedback. In a closed loop control system, sensors monitor the actual output and compare it to the desired setpoint. If discrepancies arise, the control system makes adjustments to the inputs in order to minimize the error and bring the system back to the desired state. This feedback mechanism is key to enhancing the stability and accuracy of the process being controlled.

In contrast, open loop control systems do not use feedback to adjust their functioning; they operate based on predefined settings and do not correct errors that may arise in the output. Therefore, they lack the responsiveness that closed loop systems possess. Feedforward control anticipates changes and adjusts inputs proactively before errors occur, rather than reacting to feedback after the fact. On the other hand, discrete control deals with systems that operate in distinct states rather than through continuous adjustments. Understanding these distinctions clarifies why closed loop control is the most appropriate type for maintaining continuous adjustments to achieve desired outcomes in a system.