ABSTRACT
This chapter deals with state-space models. A complete discussion of all types of input-output models would be virtually impossible. The chapter focuses on an exemplary subclass of input-output models, those that are linear and time-invariant (LTI). Even when LTI models are somewhat inaccurate, they have so many advantages over more accurate models that they are often still used, albeit cautiously. Transfer functions are very important in classical control theory and practice. They have the advantage of being directly measurable. That is, given a physical system that is approximately LTI, its transfer function can be determined experimentally. The chapter describes transfer function models of LTI systems. A simple generalization of the RC circuit example provides a large, and very useful class of input-output models for systems. The development of the continuous-time impulse response as an input-output model for LTI continuous-time systems is analogous to that for discrete-time.
