Design of a camera stabilizer system for robotic fish based on feedback-feedforward control

This paper presents a novel approach for a visual system of robotic fish to reduce the instability of camera image caused by the inherent periodic yawing of the fish head. In order to acquire the stable image from the camera located inside of the fish head, a camera stabilizer for the visual system is designed. Meanwhile, an Inertial Measurement Unit (IMU) with nine degrees-of-freedom (DoFs) is employed to maintain the attitude of the camera stable with respect to the inertial frame. To accurately describe the stabilizer system characteristics, a simple and effective system model is built. Moreover, a feedback-feedforward controller is proposed to mitigate the periodic swing effect and obtain stable and clear camera image when the robotic fish is swimming. Finally, the simulation and experiments both verified the effectiveness of the mechanism design for camera stabilizer and the corresponding feedback-feedforward control approach for enhancing the stability of images.