Underwater navigation based on passive electric sense: New perspectives for underwater docking

Abstract

In underwater robotics, several homing and docking techniques are currently being investigated. They aim to facilitate the recovery of underwater vehicles, as well as their connection to underwater stations for battery charging and data exchange. Developing reliable underwater docking strategies is a critical issue especially in murky water and/or in confined and cluttered environments. Commonly used underwater sensors such as sonar and camera can fail under these conditions. We show how a bio-inspired sensor could be used to help guide an underwater robot during a docking phase. The sensor is inspired by the passive electro-location ability of electric fish. Exploiting the electric interactions and the morphology of the vehicle, a sensor-based reactive control law is proposed. It allows the guidance of the robot toward the docking station by following an exogenous electric field generated by a set of electrodes fixed to the environment. This is achieved while avoiding insulating perturbative objects. This control strategy is theoretically analysed and validated with experiments carried out on a setup dedicated to the study of electric sense. Though promising, these results are but a first step towards the implementation of an approach to docking in more realistic conditions, such as in turbid salt water or in the presence of conductive perturbative objects.