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Amplitude information-frequency characteristics for multi-frequency excitation of underwater active electrolocation systems

Underwater active electrolocation technology is a new kind of technology for underwater detection and environmental perception, whose discovery was inspired by the active electrolocation systems of weakly electric fish. The amplitude information-frequency characteristics (AIFC) obtained by an underwater active electrolocation system (UAES) can effectively assess information about probed objects, such as their material composition, shape, and conductivity. Traditionally, single-frequency excitation has been employed in a UAES, which can make object detection inefficient and time-consuming. We employed multi-frequency signals for excitation in a UAES, to improve the efficiency of detection. We used three kinds of multi-frequency excitation signals—square wave, single pulse, and biphasic pulse, to detect objects under water. To improve the accuracy of measurements, we developed an AIFC recognition algorithm. The experimental results showed that the multi-frequency excitation detection method is effective and feasible. We demonstrated that the electrodes are strongly coupled to the UAES and can result in non-negligible errors that have often been previously ignored. In addition, graphite electrodes performed much better than titanium electrodes for multi-frequency signal detection, and bio-inspired multi-frequency pulse excitation signals gave more accurate results than the square-wave signal.