Volume 27 Issue 5 - Publication Date: 1 May 2008
Active Electrolocation for Underwater Target Localization
James R. Solberg, Kevin M. Lynch and Malcolm A. MacIver Department of Mechanical Engineering R. R. McCormick School of Engineering and Applied Science, Northwestern University, Evanston, IL 60208-3111, USA
We explore the capabilities of a robotic sensing system designed to locate objects underwater through active movement of an electric field emitter and sensor apparatus. The system is inspired by the biological phenomenon of active electrolocation, a sensing strategy found in two groups of freshwater fishes known to emit weak electric fields for target localization and communication. An analytical model for the observation of simple targets is used to qualitatively predict some characteristics of the sensor including the detection distance as a function of sensor noise. We characterize the performance of the robot using different automatic electrolocation controllers, objects and water salinities. We demonstrate successful electrolocation both in the conditions in which it is naturally observed (i.e. in low conductivity water) as well as in conditions in which it is not observed (i.e. in water of ocean salinity). For the electrolocation experiments using an active controller based on a probabilistic sensor model, the median positional estimation error for spheres is ~ 3% of sphere diameter. Spheres were detected at distances similar to the distance between the two field electrodes.
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