Research AritcleOutput feedback adaptive fuzzy control of uncertain MIMO nonlinear systems with unknown input nonlinearities

•The output feedback adaptive fuzzy control of nonlinear MIMO systems is considered.•The nonlinear systems have unknown nonlinear functions.•The nonlinear systems have unknown input nonlinearities and unknown input gains.•The states of the nonlinear systems are not available for measurement.•The semi-global asymptotic stability of the closed-loop system is guaranteed.

An adaptive fuzzy output feedback controller is proposed for a class of uncertain MIMO nonlinear systems with unknown input nonlinearities. The input nonlinearities can be backlash-like hysteresis or dead-zone. Besides, the gains of unknown input nonlinearities are unknown nonlinear functions. Based on universal approximation theorem, the unknown nonlinear functions are approximated by fuzzy systems. The proposed method does not need the availability of the states and an observer based on strictly positive real (SPR) theory is designed to estimate the states. An adaptive robust structure is used to cope with fuzzy approximation error and external disturbances. The semi-global asymptotic stability of the closed-loop system is guaranteed via Lyapunov approach. The applicability of the proposed method is also shown via simulations.