Robust position control with combining inner and outer Loop based on sliding mode for a Solar Powered Autonomous underwater vehicle (AUV)

Tracking the movement path is one of the most important factors of system control in intelligent subsurface robots. In this paper, the robust position control for a Solar Powered AUV is developed using nonlinear modeling. Because the used controller does not have the disadvantages of using a linear controller around a working point. Energy problems have been solved through the use of solar energy and will increase efficiency in a longer mission. That is, reducing the number of energy storage elements in these types of robots will increase other capabilities in these types of models. An attempt has been made to improve the movement path by relying on the combination of two Loops. In order to reduce the complexity of the controller, two models based on kinematics and dynamics of a Solar Powered AUV system with 6-DoF have been developed and generalized. In this modelling, the inner loop representing the system is used for virtual tracking with the back-stepping control technique and the outer loop representing the speed control, in convergence with the inner loop to oppose uncertainties and disturbances (internal-external) based on the sliding mode. A virtual reference input for robust nonlinear control is applied to the first part and then a real control input is applied to the second system. The closed-loop stability of the proposed subsystems is guaranteed so that it has a uniform final performance based on the Lyapunov stability criteria. Next, in order to guarantee the performance of the controllers, in addition to the different scenarios that have been introduced, in the simulation, external disturbances have also been applied to the system. The results of the outputs show the capability of the closed loop system in dealing with disturbances and the proper performance is in tracking the movement path and proves the feasibility and effectiveness.