The design of controllers utilizing state feedback is the subject of this chapter. We first present a system test for controllability and observability. Using the powerful notion of state variable feedback, we introduce the pole placement design technique.

Ackermann’s formula can be used to determine the state variable feedback gain matrix to place the system poles at the desired locations. The closed-loop system pole locations can be arbitrarily placed if and only if the system is controllable.

When the full state is not available for feedback, we utilize an observer. The observer design process is described and the applicability of Ackermann’s formula is established. The state variable compensator is obtained by connecting the full-state feedback law to the observer.

We consider optimal control system design and then describe the use of internal model design to achieve prescribed steady-state response to selected input commands. The chapter concludes by revisiting the Sequential Design Example: Disk Drive Read System.