ABSTRACT
Rapid advances in digital system technology have radically altered the control system design options. It has become routinely practicable to design very complicated digital controllers and to carry out the extensive calculations required for their design. These advances in implementation and design capability can be obtained at low cost because of the widespread availability of inexpensive and powerful digital computers and their related devices. A digital control system uses digital hardware, usually in the form of a programmed digital computer, as the heart of the controller. A typical digital controller has analog components at its periphery to interface with the plant. It is the processing of the controller equations that distinguishes analog from digital control. Analogous to the differential equations that describe continuous-time systems, the input-output behavior of a discrete-time system can be described by difference equations. A linear step-invariant discrete-time system is said to be input-output stable if its pulse response decays to zero asymptotically.
