Indirect adaptive fuzzy output control for SISO nonlinear systems with unknown control direction

This paper presents an indirect adaptive fuzzy output control for a class of uncertain single-input single-output(SISO) nonlinear systems with unknown control direction. A state observer is designed to estimate the unmeasured state, the adaptive fuzzy controller is designed in the presence of only system output is available for measurement, and a robust controller is used to compensate for the lumped errors. The Nussbaum gain is incorporated in the robust controller to estimate the unknown control direction, and the parameter adaptive laws are designed by the fuzzy basis functions rather than its filtering. The proposed design scheme guarantees that all the signals in the resulting closed-loop systems are bounded and the tracking errors converge asymptotically to zero. A simulation example is used to demonstrate the effectiveness of the proposed scheme.