Adaptive Fuzzy Control for a Class of Multivariable Nonlinear Systems with Unknown Control Direction

In this paper, a direct adaptive fuzzy control scheme is presented for a class of uncertain MIMO nonlinear systems with unknown sign of the control gain matrix. Within this scheme, fuzzy systems are employed to approximate an unknown ideal controller which can achieve the control objectives. The free parameters of the used fuzzy systems are adjusted online using the error between the unknown ideal controller and the fuzzy controller. Unlike previous works, the Nussbaum function technique is not used to deal with the unknown sign of the control gain matrix. In fact, in this paper, the unknown control direction is considered as an unknown constant parameter and it is estimated online by an appropriate adaptation law. The stability of the closed-loop system is analyzed using a Lyapunov approach. Simulation results are given to demonstrate the effectiveness of the proposed control design. (C) 2017, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.