Reliable Computations

State Space

The state-space representation is the most reliable LTI model to use for computer analysis. This is one of the reasons for the popularity of "modern" state-space control theory. Stable computer algorithms for eigenvalues, frequency response, time response, and other properties of the quadruple are known [5] and implemented in this toolbox. The state-space model is also the most natural model in MATLAB's matrix environment.

Even with state-space models, however, accurate results are not guaranteed, because of the problems of finite-word-length computer arithmetic discussed in the last section. A well-conditioned problem is usually a prerequisite for obtaining accurate results and makes it important to have reasonable scaling of the data. Scaling is discussed further in the "Scaling" section later in this chapter.

Choice of LTI Model

Transfer Function