Underwater Surface Flow Velocity Sensor Based on Single Side Stray Field of Permanent Magnet

Flow perception, as unique for the underwater creature, is also the key component for underwater robots. However, due to strict limitations on power consumption, flow resistance, volume, and weight, achieving flow perception ability artificially is not easy in underwater robots. Different from the existing sensors, by using the stray field of the permanent magnet, a novel surface flow velocity sensor is proposed with zero excitation power consumption, nearly zero flow resistance, and considerable signal output. In this article, based on the derived formula of electromagnetic induction with the stray field, the relationship between the electrode output voltage, the permanent magnet stray field, the surface flow field boundary layer, and the electrode position is established, and the spatial sensitivity distribution of the sensor unit to surface flow field with optimal electrode position is studied. By using a flexible surface printed electrode, when the fluid flows through the magnetic field area on the electrode surface, induced voltage proportional to the velocity is generated. Finally, the flow velocity perception ability of the sensor is verified by finite element simulation and experiments, and the sensitivity coefficients of the sensor under different electrode positions are compared. The proposed sensor can be used for any underwater vehicle to realize the perception of the surface flow field without damaging the streamline shape. The intrinsic sensitivity of the sensor unit is
$1.6 \mathrm {mV}/(\mathrm {m}\cdot \mathrm {s}^{-1}) $
with the weight of 7.8 g.