Robust indirect adaptive fuzzy control using Nussbaum gain for a class of SISO nonlinear systems with unknown directions

This paper deals with indirect adaptive control using fuzzy systems for a class of uncertain SISO systems with unknown control gain sign. The uncertain nonlinearities of the systems are captured by fuzzy systems that have been proven to be universal approximators and the Nussbaum -type function is used to deal with the unknown control gain sign. The proposed control scheme completely overcomes the singularity problem that occurs in the indirect adaptive feedback linearizing control. Projection in the estimate parameters is not required and the stability analysis of the closed-loop system is performed using Lyapunov approach. Simulation results are provided to verify the effectiveness of the proposed design.