REF615E-D HBFDACADANB1BNN1XD is contrary to the frequency domain analysis of classical control theory

In contrast to the frequence-domain analysis of classical control theory, modern control theory utilizes time-domain representation of state vectors in space, [citation needed] a mathematical model of a physical system consisting of a set of inputs, outputs, and state variables associated with first-order differential equations. In order to abstract from the number of inputs, outputs, and states, variables are represented as vectors, and differential and algebraic equations are written in matrix form (the latter is only possible if the dynamical system is linear). State-space representation (also known as the “time-domain approach”) provides a convenient and compact way to model and analyze systems with multiple inputs and outputs. With inputs and outputs, we’re going to have to write down the Laplace transform to encode all the information in the system. Unlike the frequency-domain approach, the use of state-space representations is not limited to systems with linear components and zero initial conditions. “State space” means the space with the state variable as the axis. The state of the system can be expressed as a point in that space.