Abstract
Emerging opportunities in the exploration of inland water bodies, such as underwater mining of flooded open pit mines, require accurate real-time positioning of multiple underwater assets. In the mining operation scenarios, operational requirements deny the application of standard acoustic positioning techniques, posing additional challenges to the localization problem. This paper presents a novel underwater localization solution, implemented for the ¡VAMOS! project, based on the combination of raw measurements from a short baseline (SBL) array and an inverted ultrashort baseline (iUSBL). An extended Kalman filter (EKF), fusing IMU raw measurements, pressure observations, SBL ranges, and USBL directional angles, estimates the localization of an underwater mining vehicle in 6DOF. Sensor bias and the speed of sound in the water are estimated indirectly by the filter. Moreover, in order to discard acoustic outliers, due to multipath reflections in such a confined and cluttered space, a data association layer and a dynamic SBL master selection heuristic were implemented. To demonstrate the advantage of this new technique, results obtained in the field, during the ¡VAMOS! underwater mining field trials, are presented and discussed.
Highlights
Underwater technologies constitute a major engineering topic, as exploration and exploitation tasks rely on unmanned underwater vehicles (UUVs) with some level of autonomy, capable of withstanding harsh environment conditions
As the calculation of slant ranges depends on the speed of sound, we developed our observation model to be able to estimate this parameter, in an indirect manner, which is estimated by the extended Kalman filter (EKF)
The results presented are based on real data acquired during the ¡VAMOS! field trials, conducted at Silvermines in the Republic of Ireland, during September and October of 2018
Summary
Underwater technologies constitute a major engineering topic, as exploration and exploitation tasks rely on unmanned underwater vehicles (UUVs) with some level of autonomy, capable of withstanding harsh environment conditions. Considering that the positioning measurement is computed at the array side, the iUSBL configuration makes the positioning references readily available on board the UUV, facilitating its integration into the data fusion stream, with minimal time delay [8,9] This overall configuration allows positioning references to be computed on both ends, i.e., the SBL array can track all underwater targets, while each underwater vehicle is able to localize itself with respect to the surface vessel using the iUSBL transponder. The CC constitutes the operations center, where pilots drive the MV and the LARV inside a virtual reality environment This virtual representation of the underwater scenario is constantly being updated, as the mining work progresses, based on information collected by the sensors on board the MV itself and further enriched with data provided by EVA, a surveying AUV
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