On the role of context in hierarchical fuzzy controllers

This article analyzes the role of context in hierarchical fuzzy controllers based on the decomposition of the input space. The usual consideration in most hierarchical fuzzy systems is the reduction of dimensionality problems. This article will analyze how to profit from the qualities of context as a key question in the definition of a fuzzy controller, to reduce the design efforts by making it easier to introduce the expert knowledge in that process. The idea is to use the output of a level of the hierarchy as the method to define (or adjust) the normalization functions (considered as contextual information) applied to the variables of the following level of that hierarchy. Two different situations will be analyzed, including an application example for each case. In the first case the decomposition will affect variables placed at the same level of description (abstraction) regarding the problem to be solved. In the second case, the decomposition process works on variables placed at different levels of description of the problem (descriptions with a different level of abstraction).