The State Variable Approach

Design methods presented in Chaps. 4 and 5 constitute what is known now as Classical Control. One of the features of classical control is that it relies on what is known as the input–output approach, i.e., the use of a transfer function. This means that a transfer function is like a black box receiving an input and producing an output, i.e., nothing is known about what happens inside the black box. On the contrary, the state variable approach allows to study what happens inside the system.