Self-tuning control of autonomous underwater vehicles based on discrete variable structure system

This paper presents a discrete-time quasi-sliding mode controller and a self-tuning controller of autonomous underwater vehicles with parameter uncertainties and long sampling interval, which are based on the variable structure system. The proposed control systems are designed to track the desired path and each component of the switching gain can be determined separately one another. The discrete quasi-sliding mode controller is robust to the uncertainties, and reaching condition of the control system is satisfied for any initial condition. The self-tuning controller based on discrete VSS prevents the fluctuation of the estimated parameters which can occur during the parameter adaptation. These controllers with the reduced switching region are actually applicable to the tracking control of an AUV having discrete measurements and parameter uncertainties in deep sea environments. Simulation results for motion control of an autonomous underwater vehicle which acquires position informations with a discrete interval show the effectiveness of the proposed technique