H infinity robust controller comparison with PD like fuzzy logic controller for an AUV control

With the increasing usage of autonomous underwater vehicles in offshore applications, it has been important to have a controller that can satisfy a convincing performance throughout the mission. Due to non-linear and time varying dynamic, controlling this vehicle has some special difficulties. Modeling errors that may exist and Uncertainties which associated with the environment firstly evokes that the idea of a robust controller to control the underwater robot. For this purpose, after the linearization of underwater robot model with six degrees of freedom at the optimum operating point, then design H_infinity controller. Furthermore fuzzy logic controller which can works with nonlinear model and unpredictable uncertainty Such as sea currents which influence on autonomous underwater vehicle performance is designed. Finally compare obtained results in fuzzy logic controller with H_infinity robust controller. As shown in simulation results fuzzy logic controller has better performance in the presence of uncertainties in compare with H_infinity robust controller.