145 Feedback controllers

The engineer Watt produced various controllers (governors) for steam engines and developed the principle of feedback control. The output is fed through a machine back into the input. Consider a plant given by a linear system $G$ $(m\times k)$ and a controller represented by a linear system $-K$ $(k\times m)$. The output from $G$ is fed back into the input. The minus sign indicates that we want negative feedback (if the engine goes too fast, the controller will slow it down).