Mid-water current aided localization for autonomous underwater vehicles

Abstract

Survey-class Autonomous Underwater Vehicles (AUVs) typically rely on Doppler Velocity Logs (DVL) for precision localization near the seafloor. In cases where the seafloor depth is greater than the DVL bottom-lock range, localizing between the surface and the seafloor presents a localization problem since both GPS and DVL observations are unavailable in the midwater column. This work proposes a solution to this problem that exploits the fact that current profile layers of the water column are near constant over short time scales (in the scale of minutes). Using observations of these currents obtained with the Acoustic Doppler Current Profiler (ADCP) mode of the DVL during descent, along with data from other sensors, the method discussed herein constrains position error. The method is validated using field data from the Sirius AUV coupled with view-based Simultaneous Localization and Mapping (SLAM) and on descents up to 3km deep with the Sentry AUV.

Long-Term Inertial Navigation Aided by Dynamics of Flow Field Features

“…Such measurements can be obtained by using an acoustic Doppler current profiler (ADCP) or the current profiling function on some DVLs, which are nowadays becoming standard for small AUVs. With such a sensor suite, improved navigation performance, although with theoretically unbounded uncertainty, can be potentially achieved in mid-depth applications utilizing methods proposed by Stanway [34] or Medagoda et al [37] that overlap the consecutive current profiling measurements. We aim at providing long-term performance improvement to inertial navigation systems by taking advantage of the information contained in large-scale ocean current simulation.…”

“…In this work, we consider the relative flow velocity measurement to be obtained by an ADCP. It has been widely implemented in many marine engineering applications [53] including related current-aided navigation techniques for AUV descending [37]. Given the pre-loaded current velocity map Φ(p {n} , t), the measurement model can be described asẑ…”

“…This approach can also be implemented in conjunction with existing current-aided navigation schemes aiming at more accurate vehicle velocity tracking (e.g. [33] or [37]) to further improve the navigation performance of an AUV. In long-distance, mid-depth AUV missions where neither frequent surfacing nor constant bottom-tracking is available, the proposed current-aided navigation concept can be applied to improve the inertial navigation performance.…”

“…By closing this knowledge gap, researchers have been utilizing the background flow dynamics in various aspects of underwater robotics, including path planning and vehicle guidance [20]- [22], multi-vehicle cooperative control [23]- [25], optimal sensing [26]- [29], sensor network mobility analysis [30], [31], and mobile sensor allocation [32]. Nonetheless, to the best of our knowledge, the background flow dynamics has not been well exploited for underwater localization and navigation problems with only a few exceptions [33]- [37].…”

“…Their navigation scheme focuses on gliders that perform dead reckoning using depth and attitude sensors instead of initial navigation systems and requires the vehicles to resurface at regular intervals. Medagoda et al [34], [37] focused on the navigation performance during vehicle descent by utilizing the fact that ocean currents are approximately invariant within a short period of time. Similarly, Hegrenaes and Berglund [33] only considered their DVL water-tracking technique as an intermediate approach to bridge the gap between other more reliable global localization techniques involving GPS or USBL.…”