Synchronous-clock range-angle relative acoustic navigation: a unified approach to multi-AUV localization, command, control, and coordination

© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Rypkema, N., Schmidt, H., & Fischell, E. Synchronous-clock range-angle relative acoustic navigation: a unified approach to multi-AUV localization, command, control, and coordination. Journal of Field Robotics, 2(1), (2022): 774–806, https://doi.org/10.55417/fr.2022026.This paper presents a scalable acoustic navigation approach for the unified command, control, and coordination of multiple autonomous underwater vehicles (AUVs). Existing multi-AUV operations typically achieve coordination manually by programming individual vehicles on the surface via radio communications, which becomes impractical with large vehicle numbers; or they require bi-directional intervehicle acoustic communications to achieve limited coordination when submerged, with limited scalability due to the physical properties of the acoustic channel. Our approach utilizes a single, periodically broadcasting beacon acting as a navigation reference for the group of AUVs, each of which carries a chip-scale atomic clock and fixed ultrashort baseline array of acoustic receivers. One-way travel-time from synchronized clocks and time-delays between signals received by each array element allow any number of vehicles within receive distance to determine range, angle, and thus determine their relative position to the beacon. The operator can command different vehicle behaviors by selecting between broadcast signals from a predetermined set, while coordination between AUVs is achieved without intervehicle communication by defining individual vehicle behaviors within the context of the group. Vehicle behaviors are designed within a beacon-centric moving frame of reference, allowing the operator to control the absolute position of the AUV group by repositioning the navigation beacon to survey the area of interest. Multiple deployments with a fleet of three miniature, low-cost SandShark AUVs performing closed-loop acoustic navigation in real-time provide experimental results validated against a secondary long-baseline positioning system, demonstrating the capabilities and robustness of our approach with real-world data.This work was partially supported by the Office of Naval Research, the Defense Advanced Research Projects Agency, Lincoln Laboratory, and the Reuben F. and Elizabeth B. Richards Endowed Funds at WHOI

Memory-efficient approximate three-dimensional beamforming

Author Posting. © Acoustical Society of America, 2020. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 148(6), (2020): 3467-3480, doi:10.1121/10.0002852.Localization of acoustic sources using a sensor array is typically performed by estimating direction-of-arrival (DOA) via beamforming of the signals recorded by all elements. Software-based conventional beamforming (CBF) forces a trade-off between memory usage and direction resolution, since time delays associated with a set of directions over which the beamformer is steered must be pre-computed and stored, limiting the number of look directions to available platform memory. This paper describes a DOA localization method that is memory-efficient for three-dimensional (3D) beamforming applications. Its key lies in reducing 3D look directions [described by azimuth/inclination angles (ϕ, θ) when considering the array as a whole] to a single variable (a conical angle, ζ) by treating the array as a collection of sensor pairs. This insight reduces the set of look directions from two dimensions to one, enabling computational and memory efficiency improvements and thus allowing direction resolution to be increased. This method is described and compared to CBF, with comparisons provided for accuracy, computational speedup, and memory usage. As this method involves the incoherent summation of sensor pair outputs, gain is limited, restricting its use to localization of strong sources—e.g., for real-time acoustic localization on embedded systems, where computation and/or memory are limited.This work was partially supported by the Office of Naval Research, the Defense Advanced Research Projects Agency, and Lincoln Laboratory.2021-06-0

Underwater & out of sight: towards ubiquity in underwater robotics

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2019.The Earth's oceans holds a wealth of information currently hidden from us. Effective measurement of its properties could provide a better understanding of our changing climate and insights into the creatures that inhabit its waters. Autonomous underwater vehicles (AUVs) hold the promise of penetrating the ocean environment and uncovering its mysteries; and progress in underwater robotics research over the past three decades has resulted in vehicles that can navigate reliably and operate consistently, providing oceanographers with an additional tool for studying the ocean. Unfortunately, the high cost of these vehicles has stifled the democratization of this technology. We believe that this is a consequence of two factors. Firstly, reliable navigation on conventional AUVs has been achieved through the use of a sophisticated sensor system, namely the Doppler velocity log (DVL)-aided inertial navigation system (INS), which drives up vehicle cost, power use and size. Secondly, deployment of these vehicles is expensive and unwieldy due to their complexity, size and cost, resulting in the need for specialized personnel for vehicle operation and maintenance. The recent development of simpler, low-cost, miniature underwater robots provides a solution that mitigates both these factors; however, removing the expensive DVL-aided INS means that they perform poorly in terms of navigation accuracy. We address this by introducing a novel acoustic system that enables AUV self-localization without requiring a DVL-aided INS or on-board active acoustic transmitters. We term this approach Passive Inverted Ultra-Short Baseline (piUSBL) positioning. The system uses a single acoustic beacon and a time-synchronized, vehicle-mounted, passive receiver array to localize the vehicle relative to this beacon. Our approach has two unique advantages: first, a single beacon lowers cost and enables easy deployment; second, a passive receiver allows the vehicle to be low-power, low-cost and small, and enables multi-vehicle scalability. Providing this new generation of small and inexpensive vehicles with accurate navigation can potentially lower the cost of entry into underwater robotics research and further its widespread use for ocean science. We hope that these contributions in low-cost underwater navigation will enable the ubiquitous and coordinated use of robots to explore and understand the underwater domain.This research was funded and supported by a number of sponsors; we gratefully acknowledge them below. Defense Advanced Research Projects Agency (DARPA) and SSC Pacific via Applied Physical Sciences Corp. (APS) under contract number N66001-11-C-4115. SSC Pacific via Applied Physical Sciences Corp. (APS) under award number N66001-14-C-4031. Air Force via Lincoln Laboratory under award number FA8721-05-C-0002. Office of Naval Research (ONR) via University of California-San Diego under award number N00014-13-1-0632. Defense Advanced Research Projects Agency (DARPA) via Applied Physical Sciences Corp. (APS) under award number HR0011-18-C-0008. Office of Naval Research (ONR) under award number N00014-17-1-2474

Dexcom & Other Continuous Glucose Monitors Impact Toward Diabetic Care Management & Convenience

Continuous glucose monitor devices, such as the Dexcom, plays a huge role in lowering A1C, advancing individual diabetic management, and preventing diabetic complications. Through the following research, connections have been made between the goal of continuous glucose monitoring devices being more convenient for patients and the positive impact towards managing glucose trends and hemoglobin A1C levels

Modeling seabird group size: implications for ecological impact assessments

The purpose of this project is to model seabird flock size data to provide recommendations to the Bureau of Ocean and Energy Management for offshore wind turbine placement. Our hypothesis is that ecological characteristics influence which statistical distribution will provide the best fit to seabird flock size data. To test this, seabird species can be grouped based on shared ecological traits, such as foraging mechanism or diet

The impact of heritage investment on public attitudes to place: evidence from the Townscape Heritage Initiative (THI)

This paper is concerned with public perceptions and attitudes to heritage townscapes, and how these might be influenced by investment in such places, focused on their public realm, and building restoration and improvement as a catalyst for urban regeneration. It draws on a ten-year study of the impact of the Townscape Heritage Initiative, funded by the Heritage Lottery Fund, on a sample of 16 cases across the UK. By comparing an analysis of changes in townscape quality over this period, with changes in public perceptions (captured through the use of a household survey in all 16 cases at three points in the ten-year period), it draws empirically grounded conclusions about the influence of heritage investment on attitudes and perceptions to the quality of the local environment. The findings from the research suggests that public attitudes are positively influenced by programmes of investment in the built heritage, but that this influence is complex and is not as robust as the physical regeneration itself. The paper also reflects on the relative influence of the post-2008 economic recession on public attitudes to place compared with the influence of heritage investment

Impacts of cultural dynamics on conservation of Suakin, Sudan

This article was published in the journal Proceedings of the ICE- Engineering Sustainability [http://www.icevirtuallibrary.com/content/serial/ensu]. Permission is granted by ICE Publishing to print one copy for personal use. Any other use of these PDF files is subject to reprint fees.The aim of this work was to explore the impact of local cultural dynamics on the conservation of the built heritage of Suakin, an abandoned historic port on the Red Sea coast of Sudan, through a collaborative stakeholder approach. Key representatives of local stakeholder groups attended a two-day workshop and took part in a series of collaborative activities. These encompassed the production of a rank-ordered list of the key local cultural dynamics impacting on the port's conservation, agreement to a number of actions to address obstacles to conservation, identification of local cultural values collectively determined by stakeholder and confirmation of the value of an integrated conservation approach. The workshop enabled a shared understanding and responsibility between stakeholders and established a commitment to further action to address the key local cultural dynamics impacting on the conservation. This collaborative stakeholder participation represented a new step in the port's conservation and invited the development of more formal protocols to enable the equal representation and participation of stakeholders in future conservation activities and initiatives

Historic Preservation as Sustainable Development

Bill Kennedy Memorial Lecture, presented on April 07, 2010 from 6:00 PM – 7:00 PM in the Reinsch-Pierce Family Auditorium, East Architecture Building on the Georgia Tech campus.Runtime: 56:47 minutesToday the phrases “sustainable development” and “green buildings” are too often used as synonyms in the United States. And while green building technology can be an important contributor to a comprehensive sustainability strategy, it is far from the only element. On an international level the broader concept of sustainable development includes not just environmental responsibility, but also economic and social/cultural responsibility. The rehabilitation and reuse of the historic built environment is perhaps the singular strategy that simultaneously advances all three of the responsibilities of sustainable development