Hybrid system
From Free net encyclopedia
A hybrid system consists of both discrete signals and continuous signals. Often, the term hybrid dynamic system is used, to distinguish over hybrid systems such as those that combine neural nets and fuzzy logic, electrical and mechanical drivelines.
The term hybrid system refers to a mathematical representation and should not be contrued as a characterization of a physical system. The model of a physical system may be of a hybrid nature, but whether it is depends on the level of abstraction chosen for the design of the model.
So, whether a particular signal in a given system is seen as discrete or continuous, is ultimately a modeling question. A more accurate (still informal) description would then be: a hybrid model of a system consists of both discrete signals (or variables) and continuous signal or variables.
A canonical example of a hybrid model is an electronic thermostat, where the temperature, a physical quantity, is modeled as a continuous variable and the state of the heater switch (on/off) is modeled as a discrete variable.
Two basic hybrid system modeling approaches can be classified, an implicit and an explicit one. The explicit approach is often represented by a hybrid automaton or a hybrid Petri net. The implicit approach is often represented by guarded equations to result in systems of differential and algebraic equations (DAEs) where the active equations may change, for example by means of a hybrid bond graph.
External links
- IEEE CSS Committee on Hybrid Systems
- IEEE CSS CACSD Technical Committee Action Group on Hybrid Dynamic Systems
