Robust depth control of a hybrid autonomous underwater vehicle with propeller torque's effect and model uncertainty

• Published in: Ocean engineering 2021-01, Vol.220, p.108257, Article 108257
• Main Authors: Tran, Huy Ngoc, Nhut Pham, Thanh Nguyen, Choi, Sik Hyeung
• Format: Article
• Language: English
• Subjects: Autonomous underwater vehicle (AUV); Backstepping; Depth control
• ISSN: 0029-8018; 1873-5258
• DOI: 10.1016/j.oceaneng.2020.108257

This paper presents a study of depth tracking controller design for a hybrid AUV in the presence of model uncertainty and propeller torque's effect. Firstly, the six degrees of freedom (6-DOF) nonlinear equations of motion, as well as the operating mechanisms and specific characteristics of the hybrid AUV, are described. Subsequently, the model for depth-plane is extracted by decoupling and linearizing the 6-DOF AUV model. Furthermore, a nonlinear disturbance observer (NDO) is constructed to deal with the linearization errors and uncertain components in the depth-plane model. A depth tracking controller is then designed based on the backstepping technique to guarantee the tracking error converges to an arbitrarily small neighborhood of zero. Besides, the robust stability of the proposed controller concerning the propeller torque's effect and the model uncertainty is analyzed. To ensure the objectivity and feasibility of the proposed method, the depth controller is applied to the 6-DOF model of AUV so that it maintains the coupling between roll, yaw, and pitch motion. Finally, the numerical simulation is carried out via MATLAB/SIMULINK to verify the controller's effectiveness, feasibility, and stability. •The depth tracking controllers in the presence of model uncertainty, propeller torque’s effect.•Applied to the nonlinear 6-DOF AUV model.•A depth tracking controller based on the backstepping technique.•The robust stability analysis concerning the propeller torque’s effect and the model uncertainty is analyzed.