Separate Control Strategy for a Biomimetic Gliding Robotic Fish

In this article, we present a novel separate strategy to control the pitch attitude and the gliding direction for a biomimetic gliding robotic fish by the coordination of the external and internal control surfaces. First, we derive the gliding dynamics and hydrodynamics within the framework of the extended angle of attack (AOA), based on which the gliding model is decomposed into pitch and velocity terms. Next, the backstepping and model predictive controllers are designed to regulate pitch angle using a movable mass and an AOA using pectoral fins based on their control features, respectively. Further, extensive simulations encompassing separate control and path following with desired pitch attitude are conducted to verify the feasibility and superiority of the proposed control strategy. More importantly, to capture the real-time gliding states in practical environment, we develop a gliding measurement and control system. Through the system, the aquatic experiments are carried out to further verify the effectiveness of the proposed separate control strategy. The obtained results offer valuable insight into the development of complex motion control of the gliding robots, laying a solid foundation for diversified underwater missions besides visual perception and autonomous docking.