Introduction#
The aim of system modeling is to provide description methods for the evaluation of the performance of a system. These description methods should be as simple as possible, but adequate and sufficiently accurate for the investigation of a performance aspect of interest. Hence, different models may be used for the evaluation of different performance aspects.
Most real world systems can be considered to be time-variant, nonlinear dynamic and distributed, and such behavior can only be analyzed with complex models and computer-based numerical analysis. Because of their complexity, such models do not provide much design information. In fact, numerical analysis can only be performed on systems that have already been designed. Symbolic analysis techniques, however, can help us find design parameters that determine specific behavioral aspects of the system.
Most symbolic analysis techniques have a limited scope, and proper analysis techniques have to be selected for the investigation of specific performance aspects. Analysis of the influence of the dynamic behavior of a system requires a modeling technique other than the analysis of its nonlinear behavior. For this reason, we will start this overview of system modeling with a classification of systems and assign appropriate modeling techniques to each class of systems. This will be done in section Classification of systems. In the sections following this classification, we will give a short summary of the most commonly used modeling and analysis techniques. We will discuss the modeling of lumped continuous-time analog systems only.
Many idealized systems, e.g. ideal amplifiers, are considered linear, instantaneous and stationary for signals of interest.
Their ideal behavior will be described in section Linear stationary instantaneous systems. We also need techniques for modeling their non-ideal behavior: their nonlinear behavior, their dynamic behavior and time-variant behavior. Modeling of dynamic stationary linear systems is discussed in section Linear stationary dynamic systems. Modeling of nonlinear stationary and instantaneous systems will be discussed in section Fixed instantaneous nonlinear systems, and modeling of time-variant linear instantaneous systems in section Linear time-variant instantaneous systems. Some notes will be made on the modeling of combinations of non-idealities, that occur in nonlinear dynamic systems. This will be done in section Modeling of nonlinear dynamic systems.