Sliding Mode Observer-Based Heading Control for a Gliding Robotic Dolphin

This paper proposes a sliding mode observer (SMO)-based heading control method for the gliding motion of a dolphin-like gliding robot. A pair of flippers are employed to regulate gliding direction via differential actions, rather than actuators commonly used in traditional underwater gliders. The framework of the control algorithm is established based on a derived dynamic model, including an SMO, a backstepping controller, and a solver for action commands of the flippers. Considering gliding velocity is indispensable for heading control but difficult to measure practically, we design the SMO to estimate gliding velocity by data acquired from a depth sensor and an attitude and heading reference system. Afterward, the backstepping methodology is applied to derive the heading control law. Further, a solver is designed to convert the controller's instruction to deflection angles of the flippers, which can simultaneously eliminate coupled but undesired roll and sideslip. Simulation results obtained demonstrate the effectiveness of the proposed method.