Simultaneous Stabilization of Pitch and Yaw of a Gliding Robotic Fish Using Sliding Mode Control

Oceanic sustainability has been a growing global concern due to the increase of potential threats to the integrity of aquatic ecosystems. As a result, more attention has been paid to the monitoring of such environments, leading to the need for autonomous aquatic robots that are capable of monitoring them in an efficient and accurate manner. A gliding robotic fish is a type of underwater robot that stems from combining the energy-efficient underwater glider with the highly maneuverable robotic fish. For accurate trajectory control and precise sensor measurement, stabilization of both pitch and yaw during gliding is of great importance. In this paper we propose a multi-input-multi-output sliding mode controller for simultaneous stabilization of pitch and yaw. In this design, the outputs of both actuators, tail angle and center of gravity, are determined by the errors in both pitch and yaw. The effectiveness of the proposed approach is demonstrated via simulation with comparison to several alternative designs, including a pair of sliding mode controllers dealing with yaw and pitch separately, and a PI controller.