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

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

Real-Time Passive Acoustic Tracking of Underwater Vehicles

Com o crescente interesse na exploração oceânica, sistemas de localização subaquática têm sido largamente usados pela industria e comunidade cientifica. Neste trabalho foi desenvolvido um sistema de localização acústica passiva em tempo real, com uma topologia idêntica ao do ultra-short baseline. Este sistema calcula a posição a duas dimensões de uma fonte acústica submersa conhecida, com base na integração de medições da direção do som ao longo do tempo. O ângulo de chegada da onda sonora é estimado pelo atraso de fase entre os sinais adquiridos por dois hidrofones colocados perto um do outro. Esta configuração permite atenuar as diferenças nos sinais recebidos devidas a perturbações do canal acústico subaquático. Este algoritmo foi implementado em tempo real numa plataforma SoC reconfigurável (CPU ARM + FPGA), e validado com ensaios de campo realizados no mar

CES-515 Towards Localization and Mapping of Autonomous Underwater Vehicles: A Survey

Autonomous Underwater Vehicles (AUVs) have been used for a huge number of tasks ranging from commercial, military and research areas etc, while the fundamental function of a successful AUV is its localization and mapping ability. This report aims to review the relevant elements of localization and mapping for AUVs. First, a brief introduction of the concept and the historical development of AUVs is given; then a relatively detailed description of the sensor system used for AUV navigation is provided. As the main part of the report, a comprehensive investigation of the simultaneous localization and mapping (SLAM) for AUVs are conducted, including its application examples. Finally a brief conclusion is summarized

Signal Absorption-Based Range Estimator for Undersea Swarms

Submitted in partial fulfillment of the requirements for the degree of Master of Science in Mechanical Engineering at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2020.Robotic swarms are increasingly complex above the waterline due to reliable communication links. However, the limited propagation of similar signals in the ocean has impacted advances in undersea robotics. Underwater vehicles often rely on acoustics for navigation solutions; however, this presents challenges for robotic swarms. Many localization methods rely on precision time synchronization or two-way communication to estimate ranges. The cost of Chip-scale Atomic Clocks (CSACs) and acoustic modems is limiting for large-scale swarms due to the cost-per-vehicle and communications structure. We propose a single vehicle with reliable navigation as a "leader" for a scalable swarm of lower-cost vehicles that receive signals via a single hydrophone. This thesis outlines range estimation methods for sources with known signal content, including frequency and power at its origin. Transmission loss is calculated based on sound absorption in seawater and geometric spreading loss to estimate range through the Signal Absorption-Based Range Estimator (SABRE). SABRE's objective is to address techniques that support low-cost undersea swarming. This thesis's contributions include a novel method for range estimation onboard underwater vehicles that supports relative navigation through Doppler-shift methods for target bearing. This thesis develops the theory, algorithms, and analytical tools for real-world data range estimation

Closed‐loop one‐way‐travel‐time navigation using low‐grade odometry for autonomous underwater vehicles

© The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Journal of FIeld Robotics 35 (2018): 421-434, doi:10.1002/rob.21746.This paper extends the progress of single beacon one‐way‐travel‐time (OWTT) range measurements for constraining XY position for autonomous underwater vehicles (AUV). Traditional navigation algorithms have used OWTT measurements to constrain an inertial navigation system aided by a Doppler Velocity Log (DVL). These methodologies limit AUV applications to where DVL bottom‐lock is available as well as the necessity for expensive strap‐down sensors, such as the DVL. Thus, deep water, mid‐water column research has mostly been left untouched, and vehicles that need expensive strap‐down sensors restrict the possibility of using multiple AUVs to explore a certain area. This work presents a solution for accurate navigation and localization using a vehicle's odometry determined by its dynamic model velocity and constrained by OWTT range measurements from a topside source beacon as well as other AUVs operating in proximity. We present a comparison of two navigation algorithms: an Extended Kalman Filter (EKF) and a Particle Filter(PF). Both of these algorithms also incorporate a water velocity bias estimator that further enhances the navigation accuracy and localization. Closed‐loop online field results on local waters as well as a real‐time implementation of two days field trials operating in Monterey Bay, California during the Keck Institute for Space Studies oceanographic research project prove the accuracy of this methodology with a root mean square error on the order of tens of meters compared to GPS position over a distance traveled of multiple kilometers.This work was supported in part through funding from the Weston Howland Jr. Postdoctoral Scholar Award (BCC), the U.S. Navy's Civilian Institution program via the MIT/WHOI Joint Program (JHK),W. M. Keck Institute for Space Studies, and theWoods Hole Oceanographic Institution

Acoustic system for ground truth underwater positioning in DEEC's test tank

Desenvolvimento de um sistema acústico de posicionamento capaz de estimar, em tempo real, a posição tridimensional de objetos dentro do tanque de ensaios do DEEC.A obtenção desta posição "ground truth" é fundamental para o apoio a ensaios de sistemas de navegação subaquáticos e para o controlo de veículos robóticos tais como AUV's e ROV's.Development of an acoustic positioning system, capable of estimating, in real time, the three-dimensional position of an object inside the DEEC's test tank. The ability to obtain this ground truth position is fundamental to support tests of underwater navigation systems, and to the control of robotic vehicles such as AUV's and ROV's

The autonomous underwater vehicle emergency localization system: an under ice AUV tracking technology for over-the-horizon operations

There is an inherent risk of loss that accompanies any operations of Autonomous Underwater Vehicle (AUV) technology. This complexity and risk are increased for AUV missions that are conducted beneath ice and in harsh environmental conditions (i.e. extreme cold, compromised visibility, etc.). Risk-based methodologies have been developed to quantify the risk of loss for specific AUV platforms prior to deployments. Their goal is to identify and mitigate where possible the significant contributors (technical or otherwise) to the overall risk of a specific operation. Not surprisingly, there is an abundant amount of literature related to successful AUV missions; however, there has been very little published work related to AUV loss. Specifically, this author is not aware of any examples of a developed procedure to employ during an AUV loss event to date, much less specific algorithms developed to locate a missing AUV. This is a subset of the AUV tracking or positioning that is rarely given specific treatment. The motivating problem is based on the loss event of an AUV during polar operations. For example, (i) the vehicle might navigate outside of its predefined spatial area through some fault or error, or, (ii) its mission involves over-the-horizon operations, i.e. beyond the range of standard acoustical tracking technologies. In either circumstance, at the end of its pre-programmed mission, the AUV fails to return to the base station. Such an eventuality defines the need for reliable, long-range acoustic tracking capability that is able to coarsely localize the AUV and subsequently enable communications and/or recovery of the AUV. The thesis describes a novel approach for an acoustic positioning system for AUV localization in harsh environments with non-standard acoustic challenges that can be implemented using only basic acoustic technology, a basic single-beacon, singlehydrophone (SBSH) system. Inversive geometric techniques are applied for source localization of a one-way traveling, asynchronous acoustic signal. This differs from the usual methods of spherical, two-way direct flight measurement based on time of arrival (TOA), or hyperbolic, one-way time difference of arrival (TDOA) target tracking for transmission based on a purely Euclidean geometry. This is a novel approach to the problem of localizing an AUV. A second method of solving the non-linear system of equations that arise from the problem using the SBSH approach is derived. Both methods, the novel Apollonian inversion geometry localization (AIGL) and the non linear system localization (NLSL), are evaluated in simulation and using live field data. It will be shown that the novel algorithm performs comparable to the standard method of solving the nonlinear systems resulting from a SBSH approach. Furthermore, in certain situations it improves the localization result