Real-Time Velocity Vector Resolving of Artificial Lateral Line Array With Fishlike Motion Noise Suppression

The past decade has seen the rapid development of the robotic fish in many aspects. However, the velocity measurement problem has not been fully addressed, which limits the autonomy of the robotic fish. To this end, an artificial lateral line (ALL) sensor, inspired by the sensory organs of fish, is developed in this article. By measuring the deformation of the sensitive element, the local flow field around the robotic fish is sensed. According to the characteristics of fishlike motions, a fairing structure is proposed to suppress the turbulence noise and yaw motion noise caused by fishlike oscillation of the tail. This structure ensure that the flow measured by the ALL sensor is closer to laminar flow under viscous effects. Furthermore, to measure the magnitude and direction of the robotic fish velocity, an ALL sensor array is assembled by mounting multiple sensors on the robot's surface to sense the flow field distribution. Next, a kinematic-based fusion method is proposed for the array system, which obtained the real-time velocity vector of the robotic fish by solving overdetermined motion equations. The proposed ALL array system is tested on a freely swimming robotic fish, and our method achieves a mean absolute error of 0.018 m/s, a linearity ( $R^{2}$ ) of 0.951, and a position tracking error of 0.085 m. Additionally, the fairing structure is found to improve the signal-to-noise ratio by 116%.