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An extended nonlinear disturbance observer (ENDOB)-based fuzzy sliding mode control approach is proposed for single-input and single-output systems with matched and mismatched uncertainties/disturbances, and it is extended to the general nth order systems. By integrating the mismatched disturbance estimation and its derivative into the sliding mode surface, an ENDOB-based SMC method is developed for these systems. A fuzzy control system is designed to adjust the gain of the sliding mode dynamically. Compared with the nominal SMC method, the proposed method has a stronger anti-disturbance ability in the presence of matched and mismatched uncertainties/disturbances. It can ensure a satisfactory system performance and reduce the chattering. The stability of the system is proved by using Lyapunov theory. The final simulation results of two examples are provided to verify the effectiveness of the proposed control method. INDEX TERMS Matched and mismatched, fuzzy sliding mode control (FSMC), extended nonlinear disturbance observer (ENDOB), permanent magnet synchronous motor (PMSM).