A NEW METHOD OF SWITCHING SURFACE DESIGN FOR MULTIVARIABLE STRUCTURE-SYSTEM - COMMENT

This note points out some errors in the above paper.(1) It is argued t hat the proof in the main theorem is not mathematically rigorous. The control scheme requires the derivative of the sliding variable to be a vailable, which is equivalent to saying that the uncertainties of the system are measurable. This is highly impractical if not impossible to implement. The theorem also says that the proposed new switching surf ace and control scheme can guarantee robustness of the system from ini tial time to final time. This is also incorrect because the theorem on ly shows that the sliding variable tends to zero approximately, i.e., the sliding motion only occurs approximately at t=infinity. The paper also contains several misprints.