Direct adaptive fuzzy control for nonaffine nonlinear systems with unknown control direction

This paper deals with direct adaptive fuzzy control for a class of uncertain nonaffine nonlinear systems with unknown control direction. Within this scheme, a fuzzy system is used to generate directly the control input signal without dynamic system estimation. The adjustable parameters in the used fuzzy system are updated using a gradient descent adaptation algorithm that incorporates a Nussbaum-type function to deal with the unknown control direction. The stability of the closed-loop system is performed using a Lyapunov approach. Simulation results are provided to verify the effectiveness of the proposed design.