Design of a Miniature Underwater Angle-of-Attack Sensor and Its Application to a Self-Propelled Robotic Fish

This article proposes a miniature underwater angle-of-attack (AoA) sensor appropriate to self-propelled fin-actuated underwater robots, featuring real-time measurement of AoA relative to the incoming flow. Specifically, the developed sensor adopts a vane-rotating structure with a high-performance Hall chip that is responsible for detection of the angular deviation. Meanwhile, the Hall-effect-based acquisition scheme endows the device with several features, including low rotational damping, to satisfy underwater usage requirements. Another contribution is that an AoA model is derived to allow the real-time acquisition of AoA at the trailing edge of the caudal fin assumed in a quiescent flow. Based on this model, the AoA profile is obtained as theoretical reference with only the control laws required. Finally, the performance of the numerical model and the developed sensor are investigated through aquatic experiments assisted by a global visual measurement system. The experimental results demonstrate that the acquired AoA possesses over 0.97 Parson correlation coefficient with the theoretical data, verifying the effectiveness of the proposed mechatronic design. The developed AoA sensor and its application to robotic fish could provide potential assistance for the flow control and hydrodynamic optimization of fin-actuated underwater robots.