ABSTRACT
This chapter presents a simple description of a closed-loop control system, and analyses some of the main properties of feedback. It discusses the concepts of steady-state error, disturbances and disturbance rejection. The chapter shows how component characteristics may be linearized about an operating point. It also analyses the broad features of feedback control using very simple models of control system components. The unity feedback model makes it particularly easy to relate closed-loop static gain to steady-state error. The error may be calculated easily from the closed-loop gain. One simplification of the unity feedback model can be made. The simplest form of general closed-loop controller is known as a proportional controller, and corresponds to a constant gain acting on the error signal. The amplifier may be thought of as a proportional contro1ler, producing a control action proportional to the error signal.
