Observer-based direct adaptive fuzzy control for SISO nonlinear systems with unknown control direction

This paper presents observer-based direct adaptive fuzzy control for a class of uncertain single-input single-output(SISO) nonlinear systems with unknown control direction. With this scheme, 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. A state observer is designed to estimate the unmeasured state, the parameter adaptive laws are designed by the fuzzy basis functions rather than its filtering. Moreover, it does not require a priori knowledge of the control direction. 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.