Phase plane analysis tools for a class of fuzzy control systems

It is shown how linguistic system analysis can be extended to include fuzzy set definitions and can be applied to systems that are dominated by second-order process dynamics. This produces a graphical analysis tool, similar to the algebraic phase plane approach, for considering overall system performance. Using this technique the response of a rule-based system can be investigated and the influence of individual rules on overall performance can be determined, allowing a stability analysis to be carried out directly on the rule-based system. Two simple application examples show how this technique could be used. In particular, a controller design example demonstrates how trial and error methods can be removed from the controller design process and how stability analysis can be performed directly on the rule-based system