Pitching stability modeling and analysis of robotic fish propelled by oscillating flexible pectoral fins

In the process of oscillation, longitudinal disturbance is produced when pectoral fins of robotic fish produce propulsion. The disturbance leads to pitching motion of the body of robotic fish, increasing the swimming resistance and reducing the efficiency of swimming. Pitching stability model of robotic fish propelled by oscillating flexible pectoral fins is established based on the third generation of robotic fish developed by the robotics institute of BUAA in current study. It is verified that the model is a second-order linear system. In addition, the relationship between natural frequency of pitching stability system and swimming speed of the robotic fish is obtained. Finally, the effectiveness of pitching stability model is testified by the experiment.