Closed-loop systems are systems in which feedback is used to control the functioning of the system. In these systems, an output signal is measured, compared to a desired reference signal, and this error signal is used to adjust the system inputs in order to achieve the desired outcome. This feedback loop allows for continuous monitoring and adjustment of the system in real-time, resulting in improved performance, stability, and reliability. Closed-loop systems are commonly used in a wide range of applications, such as industrial control systems, autonomous vehicles, robotics, and medical devices. These systems are essential for maintaining control and ensuring optimal functioning in dynamic and unpredictable environments.