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oceans MTS/IEEE Washington (Conference)

作者： Clifford Pontbriand Norm Farr Johanna Hansen James C. Kinsey Leo-Paul Pelletier Jonathan Ware Dehann Fourie Advanced Ocean Physics and Engineering Department Woods Hole Oceanographic Institution MIT-WHOI Joint Program in Oceanography/Applied Ocean Science & Engineering CSAIL

ISBN: (纸本)9781467393744

The optical communications group at Woods Hole oceanographic Institution has demonstrated wireless optical transmission of data from a seafloor node to the Sentry AUV. This effort is based on the latest version of the optical modem under continual development at whoi, and it builds on fieldwork conducted in 2012 and 2013 during which we successfully transferred data from seafloor-deployed optical modem systems using a wire-lowered optical modem from a ship. While our previous work used a high-bandwidth optical modem for the data uplink and an acoustic modem "backlink" to control the file transfer, the optical modem described in this paper supports fully bidirectional optical communication - essentially subsea WiFi. A subordinate objective of our work was to literally map the operational space for an AUV-bottom node optical link. Armed with this spatial map, we can plan for future "connected" AUV operations in support of data mule, inspection, manipulation, and other underwater semi-autonomous tasks.

关键词： Underwater optical communications Freespace Optical modem Underwater wireless communications A UV Data mule

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Discovering Biological Hotspots with a Passively Listening AUV

Discovering Biological Hotspots with a Passively Listening A...

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IEEE International Conference on Robotics and Automation (ICRA)

作者： Seth McCammon Stewart Jamieson T. Aran Mooney Yogesh Girdhar Woods Hole Oceanographic Institution (WHOI) Woods Hole MA Department of Aeronautics and Astronautics MIT-WHOI Joint Program in Oceanography/Applied Ocean Science and Engineering Massachusetts Institute of Technology (MIT)

ISBN: (数字)9798350384574

ISBN: (纸本)9798350384581

We present a novel system which blends multiple distinct sensing modalities in audio-visual surveys to assist marine biologists in collecting datasets for understanding the ecological relationship of fish and other organisms with their habitats on and around coral reefs. Our system, designed for the CUREE AUV, uses four hydrophones to determine the bearing to biological sound sources through beamforming. These observations are merged in a Bayesian Occupancy Grid to produce a 2D map of the acoustic activity of a coral reef. Simultaneously, the AUV uses unsupervised topic modeling to identify different benthic habitats. Combining these maps allows us to determine the level of acoustic activity within each habitat. We demonstrated the system in field trials on reefs in the U.S. Virgin Islands, where it was able to autonomously discover the favored habitats of snapping shrimp (genus Alpheus).

关键词： Surveys Temperature measurement Visualization Array signal processing Habitats Marine vegetation Fish

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DESIGN OF DECISION DEVICE FOR THE ADAPTATION OF DECISION DIRECTED EQUALIZERS

DESIGN OF DECISION DEVICE FOR THE ADAPTATION OF DECISION DIR...

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IEEE International Conference on Acoustics, Speech, and Signal Processing

作者： Atulya Yellepeddi James C. Preisig Electrical Eng./Applied Ocean Physics and Eng. MIT-WHOI Joint Program Applied Ocean Physics and Engineering Woods Hole Oceanographic Institution

ISBN: (纸本)9781479903573

Adaptation of the coefficients of an equalizer usually takes place in the decision directed mode. The decision used for adaptation has a profound influence on the performance of the equalizer. In this work, we consider the influence of the probabilistic model used by a soft information decision device on the performance of the equalizer. It is shown that the equalizer output is distributed as a Gaussian Mixture, and these statistics are used to form a soft-decision device. We show that this is very near optimal in the sense of the Recursive Expected Least Squares algorithm introduced in prior work. Sub-optimal decision devices that are often more practical are also introduced and the loss of performance as a result of using these is considered.

关键词： Equalizers adaptive signal processing adaptive equalizers time-varying channels

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APPROXIMATE LEAST SQUARES PARAMETER ESTIMATION WITH STRUCTURED OBSERVATIONS

APPROXIMATE LEAST SQUARES PARAMETER ESTIMATION WITH STRUCTUR...

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IEEE International Conference on Acoustics, Speech and Signal Processing

作者： Atulya Yellepeddi James C. Preisig Electrical Eng./Applied Ocean Physics and Eng. MIT-WHOI Joint Program Applied Ocean Physics and Engineering Woods Hole Oceanographic Institution

ISBN: (纸本)9781479928941

The solution of inverse problems where the parameter being estimated has a known structure has been widely studied. In this work, we consider the situation where it is not appropriate to assume a structure for the parameter, but the observations on which the estimate are based are structured;specifically, when the observations are parametrized by a decomposable graphical model. This translates to structured sparsity of the inverse covariance matrix for Gaussian distributed observation vectors. We present an approximate least squares method which takes advantage of the structure to reduce the complexity of least squares. The approximate least squares method can be implemented recursively for even lower complexity. It is shown that the proposed method is asymptotically equivalent to least squares parameter estimation for a large number of observations. The properties of the algorithm are verified by simulation.

关键词： Least squares method variance covariance matrix Asymptotically equivalent Inverse method Parameter estimation Approximate

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A Low-Cost Entangling Drifter for Sargassum Tracking: Design and Experimental Evaluation

A Low-Cost Entangling Drifter for Sargassum Tracking: Design...

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oceanS

作者： Chase Pixa Kevin Manganini Alyson Myers Anna PM Michel MIT-WHOI Joint Program in Applied Ocean Science and Engineering Cambridge USA Applied Ocean Physics and Engineering Woods Hole Oceanographic Institution USA Fearless Fund Washington D.C. USA

Since 2011, Sargassum, a free-floating macroalgae, has been causing significant ecological and economic damage to coastal regions in the Northern Equatorial Atlantic due to its voluminous blooms. To better understand the fate and effects of Sargassum, approaches are needed to track its transport. Here we developed a low-cost drifter, designed to entangle with Sargassum, to aid in its tracking providing in situ movement data to ground-truth models and supplementing gaps in satellite imaging. The results of 27 drifter designs and five days of field trials are presented. The successful entanglement and tracking with the Sargassum demonstrated here can guide future studies to further our understanding of the movement of Sargassum in the great Atlantic Sargassum belt (GASB).

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Improved vehicle based multibeam bathymetry using sub-maps and SLAM

Improved vehicle based multibeam bathymetry using sub-maps a...

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2005 IEEE/RSJ International Conference on Intelligent Robots and Systems

作者： C. Roman H. Singh MIT/WHOI Joint Program in Applied Ocean Science and Engineering Massachusetts Institute of Technology Cambridge MA USA Department of Applied Ocean Physics and Engineering Woods Hole Oceanographic Institution Woods Hole MA USA

This paper presents an algorithm to improve sub-sea acoustic multibeam bottom mapping based on the simultaneous mapping and localization (SLAM) methodology. Multibeam bathymetry from underwater water vehicles can yield valuable large scale terrain maps of the sea door, but the overall accuracy of these maps is typically limited by the accuracy of the vehicle position estimates. The solution presented here uses small bathymetric patches created over short time scales in a sub-mapping context. These patches are registered with respect to one another and assembled in a single coordinate frame to produce a more accurate terrain estimate and provide improved renavigation of the vehicle trajectory. The mapping is implemented using a delayed state extended Kalman filter (EKF) and results are shown for a real world multibeam data set collected at the mid-Atlantic ridge using the JASON ROV.

关键词： Simultaneous localization and mapping Terrain mapping Marine vehicles Underwater vehicles Underwater acoustics Large-scale systems Yield estimation Assembly Delay Remotely operated vehicles

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Visually augmented navigation in an unstructured environment using a delayed state history

Visually augmented navigation in an unstructured environment...

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IEEE International Conference on Robotics and Automation (ICRA)

作者： R. Eustice O. Pizarro H. Singh MIT/WHOI Joint Program in Applied Ocean Science and Engineering Massachusetts Institute of Technology Cambridge MA USA Department of Applied Ocean Physics and Engineering Woods Hole Oceanographic Institution Woods Hole MA USA

This work describes a framework for sensor fusion of navigation data with camera-based 5 DOF relative pose measurements for 6 DOF vehicle motion in an unstructured 3D underwater environment. The fundamental goal of this work is to concurrently estimate online current vehicle position and its past trajectory. This goal is framed within the context of improving mobile robot navigation to support sub-sea science and exploration. Vehicle trajectory is represented by a history of poses in an augmented state Kalman filter. Camera spatial constraints from overlapping imagery provide partial observation of these poses and are used to enforce consistency and provide a mechanism for loop-closure. The multi-sensor camera + navigation framework is shown to have compelling advantages over a camera-only based approach by: 1) improving the robustness of pairwise image registration, 2) setting the free gauge scale, and 3) allowing for a unconnected camera graph topology. Results are shown for a real world data set collected by an autonomous underwater vehicle in an unstructured undersea environment.

关键词： Navigation Delay History Cameras Underwater vehicles Robot vision systems Sensor fusion Motion measurement Mobile robots Robustness

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Micro-bathymetric mapping using acoustic range images

Micro-bathymetric mapping using acoustic range images

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oceanS

This work focuses on the creation of high resolution micro-bathymetric maps using a high frequency pencil beam sonar. These maps typically cover areas of 10's to 100's of square meters. Data is collected using a sonar mounted to an underwater vehicle that can be positioned at discrete locations on the sea floor or flown in a survey pattern above the bottom. Specifically, we are focused on improving the accuracy of these terrain maps by merging sonar pings taken from multiple vantage points over the same location. This requires the adaption of data registration techniques to handle errors related to the sonar sensor. The registration can also be modified to incorporate the navigation data available from an instrumented underwater vehicle. A two axis scanning sonar was used to gather data in the form of densely sampled range images. The data registration works on the 3D projection of these range images in a scan-matching manner. Through this process regions occluded in a single scan are filled with data available from other scans and individual pings which show a poor return are removed. Refined estimates of the scan vantage points are also generated during the registration. The initial estimates of these locations are provided by navigation data. The practical application of this work complements photographic mapping when visibility is limited. It also provides additional measurements which can be used to improve vehicle navigation.

关键词： Sonar navigation Sonar measurements Remotely operated vehicles Underwater vehicles Sea floor Underwater acoustics Layout oceans Acoustical engineering Acoustic beams

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Corrigendum to “Non-linear singularity formation for circular vortex sheets”

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Quarterly of applied Mathematics 2024年第2期82卷 449-450页

作者： Murray, Ryan Wilcox, Galen Department of Mathematics North Carolina State University Raleigh NC 27607 MIT-WHOI Joint Program in Oceanography/Applied Ocean Science & Engineering Cambridge MA 02139 and Woods Hole MA 02543

Abstract: This paper serves as a short corrigendum, describing an error in the derivation of the linearized equation. The main theorems remain correct, but they are based upon an incorrect linearization of the Birkhoff-Rott equation and hence are not directly applicable to the original physical problem.

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Adaptive multi-altitude search and sampling of sparsely distributed natural phenomena

Adaptive multi-altitude search and sampling of sparsely dist...

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IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)

作者： Jessica E. Todd Seth McCammon Yogesh Girdhar Nicholas Roy Dana Yoerger Department of Aeronautics and Astronautics MIT-WHOI Joint Program in Applied Ocean Science and Engineering at the Woods Hole Oceanographic Institution (WHOI) Massachusetts Institute of Technology (MIT) Applied Ocean Physics and Engineering Department Woods Hole Oceanographic Institution Woods Hole MA USA Department of Aeronautics and Astronautics Massachusetts Institute of Technology

ISBN: (数字)9798350377705

ISBN: (纸本)9798350377712

In this paper, we propose a novel method for autonomously seeking out sparsely distributed targets in an unknown underwater environment. Our Sparse Adaptive Search and Sample (SASS) algorithm mixes low-altitude observations of discrete targets with high-altitude observations of the surrounding substrates. By using prior information about the distribution of targets across substrate types in combination with belief modelling over these substrates in the environment, high-altitude observations provide information that allows SASS to quickly guide the robot to areas with high target densities. A maximally informative path is autonomously constructed online using Monte Carlo Tree Search with a novel acquisition function to guide the search to maximise observations of unique targets. We demonstrate our approach in a set of simulated trials using a novel generative species model. SASS consistently outperforms the canonical boustrophedon planner by up to 36% in seeking out unique targets in the first 75-90% of time it takes for a boustrophedon survey. Additionally, we verify the performance of SASS on two real world coral reef datasets.

关键词： Surveys Adaptation models Monte Carlo methods Adaptive systems Marine vegetation Substrates Intelligent robots

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