Sensing capacitance of underwater objects in bio-inspired electrosense

Certain electric fish use a self-generated AC electric field to navigate and hunt. Thousands of sensors on the surface of the fish´s body detect the pattern of amplitude and phase distortions of the field caused by nearby objects. Prior research has suggested that phase distortions may be especially useful for recognition of live objects. Here we present the first study of the utility of phase information in a robotic implementation of active electrosense. Using our robotic implementation, we investigated how the phase information depends on the frequency of the emitted field, the conductivity of the surrounding water, and object properties. An analytical model was developed serving as qualitative explanation of the dependency. We show that in certain situations phase information enables discrimination between two objects that are otherwise very similar in the amplitude of their electric images. We also show the utility of probing objects with multiple frequencies.