Comments on “Exact Output Regulation for Nonlinear Systems Described by Takagi–Sugeno Fuzzy Models”

This letter considers the work entitled “Exact Output Regulation for Nonlinear Systems Described by Takagi-Sugeno Fuzzy Models,” published previously in the IEEE Transactions on Fuzzy S ystems, where the authors try to provide a fuzzy approach to the well-known problem of exact output regulation via a dynamic implementation of the nonlinear mapping between the state space and the steady-state zero error manifold. Two problems invalidate this methodology: 1) The results do not depend on the fuzzy structure, as claimed by the authors; and 2) the results have been obtained without properly taking into account the time-derivative of the aforementioned nonlinear mapping. Example B in the above paper is revised and corrected to illustrate these issues.