An adaptive nonlinear iterative sliding mode controller based on heuristic critic algorithm

Abstract

Aiming at the uncertainty nonlinear model influenced by the external disturbances, an adaptive nonlinear iterative sliding mode controller based on adaptive heuristic critic algorithm is presented. The proposed controller uses nonlinear hyperbolic tangent function to design the system output sliding mode function. The stability of the proposed controller can be proved via the strict boundedness of the hyperbolic tangent function and the constraint of the system input. To improve the adaptive property of the controller, the sliding mode parameters are optimized through a fuzzy system. Moreover, by defining a chattering variable and an adaptive heuristic critic function, the parameters of the fuzzy system structure can be adjusted on-line, therefore, good performance in restraining controller output chattering is achieved. Furthermore, numerical simulations were carried out on the heading control of the sail-assisted ship. The simulation results show that the controller can achieve good performance and it is robust against the perturbation from the uncertain parameters and disturbances.