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.