Consider the standard feedback block diagram shown in Figure 6-1, where disturbance inputs have been neglected. Transfer functions (and block diagrams) are used to analyze the behavior of control systems, because the algebraic expressions are easy to manipulate.
We noted in Chapter 5 that the closed-loop transfer function could be used to determine, for example, the range of controller gains that assure closed-loop stability.
PID controller algorithms were developed in Chapter 5. Here we provide a concise review of the algorithms in common use.