ABSTRACT
This chapter shows that control systems can be broadly classified into two basic categories: open-loop control systems and closed-loop control systems. In contrast to an open-loop control system, a closed-loop control system utilizes an additional measure and feedback of the controlled variable in order to compare the actual output with the desired output response. A measurement system will, therefore, be a part of a closed-loop system to provide this feedback. Compared to open-loop control systems, feedback systems or closed-loop systems are relatively complex and costly as expensive measurement devices such as sensors are often necessary to yield the feedback. Feedback systems have the desirable advantage of being less sensitive to inevitable changes in the parameters of the components in the control system. In many cases, feedback can reduce the effect of disturbance/noise on the system performance. Feedback control systems can be readily found in diverse applications and industries.
