Observer based adaptive interval type-2 fuzzy sliding mode control for unknown nonlinear systems

摘要

In this paper, a novel observer based direct adaptive interval type-2 (IT2) fuzzy sliding mode control (SMC) method is proposed for a certain class of high order unknown nonlinear dynamical systems with unmeasured states. Firstly, a high-gain observer is designed to estimate the tracking errors of the system states. Then on the basis of the observer, an IT2 fuzzy logic system (FLS) is established to approximate the equivalent control law, in which the estimate of the sliding surface function is applied as the input. The sliding mode control law is developed to guarantee the robustness of the system, in which an adaptive switching control gain is designed to handle the chattering problem. The free parameters of the controller are adjusted online by the adaptive laws. Finally, the stability of the overall closed-loop system is proved in the Lyapunov sense based on Meyer-Kalman-Yakubovich (MKY) lemma. In the proposed control system, the constraints on the knowledge of mathematical model, disturbances, and state vector can be avoid completely, and the trajectory tracking control can be achieved only using the information of system output. Simulation results demonstrate the effectiveness and the high control performance of the proposed controller.