The main objective of this research is to provide a systematic stability analysis technique for
fuzzy systems using well-established results from robust stability of a family of polynomials.
The model-based Takagi-Sugeno (1985) fuzzy control system is considered and shown to
have a dependent coefficient structure involving firing strengths. Two Kharitonov regions via
overbounding are established to facilitate the extreme results for stability test in the space of
polynomials as well as the complex plane. The criterion obtained is a sufficient condition for …

The stability conditions for Takagi-Sugeno fuzzy systems suggested in the above mentioned
article by Lo-Chen (ibid. vol. 7 (1999)) are shown by a counterexample not to be sufficient. In
reply, Lo-Chen point out that the example also indicates the fuzzy stability problem is related
to the premise part of fuzzy rules.