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Classifications of dynamical systems

Dynamical systems are mainly represented by a state that evolves in time. The input as well as the current state of a dynamical system determine the evolution of the system. Typically an output is generated from the state of the system [72]. This is a rather general definition of a dynamical system, where many different systems fit into. For investigating dynamical systems it is necessary to specify some characteristics that provide a subdivision into special classes of dynamical systems. Specific methods are available for some of these classes, thus such a classification can help to simplify the analysis.

An important characteristic of a dynamical system is whether it is continuous or discrete. Continuous systems (often called flows) are given by differential equations whereas discrete dynamical systems (often called maps) are specified by difference equations [83]. Autonomous systems are characterized by the fact that input and output are omitted from the definition [72].

An important criterion for the analysis of a dynamical system is whether it is time-dependent or not [41,42]. For time-dependent dynamical systems the function that specifies $\dot{\mathbf{x}}$ (continuous case) or $\Delta\mathbf{x}_n$ (discrete case) depends on the time itself whereas for time-independent systems this function does not change over time.

For the analysis it is very important whether a dynamical system is linear or not. Linear dynamical systems are simple to analyze as opposed to non-linear systems, which typically do have intricate dynamical behavior [83]. Often linearization at specific locations is used to get insights into these complex non-linear dynamical systems.

Using linearization, another classification of dynamical systems is crucial to separate simple cases from more complex ones. Hyperbolic dynamical systems can be analyzed by linearization efficiently, whereas non-hyperbolic systems may cause major troubles in combination with linearization [1,27]. Hyperbolic systems are structurally stable, i.e., small perturbations of the system parameters do not change the qualitative behavior of the system. Non-hyperbolic systems are difficult to investigate, occur rarely and can be considered the transitional phase between two hyperbolic systems of different nature [72].


next up previous contents
Next: Differential geometry and terms Up: Notes on the local Previous: Introduction
Helwig Löffelmann, November 1998,
mailto:helwig@cg.tuwien.ac.at.