Control of state constrained nonlinear systems with unknown dead-zone nonlinearity: A unified fuzzy dynamic surface control approach

Abstract

In this paper, we focus on the tracking control issue of state constrained nonlinear systems with unknown dead-zone nonlinearity. The systems also take into account unknown virtual control coefficients as well as external disturbances. The utilization of feasibility nonlinear transformed functions not only converts original constrained nonlinear systems into unconstrained systems, but also eliminates the difficulty of parameter selection of the barrier Lyapunov function. Under the premise of relaxing the limitation of systems, the property of the hyperbolic tangent function and adaptive estimated parameters are used to design controller to improve the robustness of control strategy. Through the combination of dynamic surface control and adaptive backstepping technology, an adaptive fuzzy dynamic surface control strategy is developed so that all signals of the closed-loop unconstrained system and original system are bounded, and states of the original system do not break predetermined constraints. Two examples are provided to illustrate that control strategy is effective.