Modeling and Designing Hierarchical Sliding Mode Controller for a 4-DOF Solar Autonomous Underwater Vehicles

—Autonomous Underwater Vehicles (AUV) are automatic equipment that can move in 6 degrees of freedom according to the motion in the water. Modeling accurately AUV is very difficult because of the influence of factors such as hydrodynamic forces, time error, and environmental noise, etc. It is important that the controller designing needs to meet the requirements of stability and suitability to specific diving equipment models. The hydrodynamic equations are established with the assumed conditions. Controlling self-propelled diving equipment is a major challenge for researchers because of the complex, and nonlinear correlation between diving and operating environments. Therefore, high-quality control systems for the AUV should exhibit the ability to update the variability of the device's hydrodynamic coefficients to achieve the desired control quality. In this study, the authors focus on building a Hierarchical Sliding Mode Controller (HSMC) for Solar Autonomous Underwater Vehicles (S-AUV), the kinematics and dynamics of the underactuated attitude control adjusting system are analyzed. More precisely, the controller is designed based on the hydrodynamic model of the S-AUV. By employing the propulsion speed, the position of the steering blades as design variables, the dive of the S-AUV is stably controlled in location, velocity, and depth. For a given set of operating parameters, the simulation result shows that the developed controller exhibits errors within the allowed range of values.