Disturbance Estimation and Rejection in an Underwater Autonomous Vehicle

The smooth operation of an underwater autonomous vehicle requires proper navigation, which can be challenging due to the highly complex environment of the ocean. Unpredictable factors, such as fast-moving waves, underwater obstacles, and external phenomena, can negatively impact the system's overall performance. In this paper, the second-order dynamics of the underwater system was modelled and implemented for yaw control to reach a desired angle. To estimate the disturbances occurring in the system accurately, an integral observer was proposed and a PID controller was designed for proper disturbance rejection. A robustness analysis with the developed controller was also conducted. The simulated results show that the designed integral observer estimates the disturbances precisely, and the proposed PID controller is effective in proper rejection control in a second-order autonomous underwater system.