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

Abstract

Flow perception, as unique for underwater creature, is also the key components for underwater robots. However, due to strictly limitation on power consumption, flow resistance, volume and weight, to achieve flow perception ability artificialy is not easy in underwater robots. Different from the existing sensors, by using the stray field of 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 paper, based on the derived formula of electromagnetic induction with stray field, the relationship between electrode output voltage, permanent magnet stray field, surface flow field boundary layer and electrode position is established, and the spatial sensitivity distribution of sensor unit to surface flow field with optimal electrode position are studied. By using 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 surface flow field without damaging the streamline shape. The intrinsic sensitivity of the sensor unit is 1.6 mV/(m∙ s^-1) with the weight of 7.8 grams.