Collaborative Research: Persistent Presence in the Ocean Interior: Developing a Low-power, Autonomous System for Geo-referenced Navigation

促进深海内部准确导航的持续存在有可能改变海洋学的开展方式。现有技术目前没有提供这种能力；然而，如果发展起来，将改变水下机器人承担的项目的范围，其航程和耐力比目前在没有考察船支持的情况下可以部署的项目更长。本研究开发了一种新的低功耗导航系统，将导航精度从1000米提高到100米。这一进展将使多条新的海洋调查路线成为可能。例如，部署协调的滑翔机机队以调查复杂的物理-生物地球化学相互作用；深入研究地形引起的混合；在整个大洋盆地规模上对海底生境/生态系统进行长期描述；以及更好地分辨水下地形陡峭区域的底层边界层过程的规模。研究人员将参与外展活动，包括本科生参与我们的研究，以及继续与当地高中机器人和环境科学课程建立合作关系。这项研究开发并测试了一种低功率声学定位系统，该系统能够在深海中进行准确的外部辅助导航。滑翔机(或滑翔机机队)在深水中作业，而自主水面机器人(ASV)则在海面上跟随。ASV以固定的间隔将其地理参考位置传输给滑翔机。然后，每个滑翔机独立地使用精确的时基(由芯片级原子钟提供)和阵列处理来确定其相对于ASV的位置。每个ASV将该相对位置估计与在接收的分组中编码的ASV的位置相结合，以计算其地理参考位置。系统性能取决于许多因素，包括车辆姿态传感器的精度。使用已经在滑翔机上使用的低功率传感器，在5000米深的地方可以达到250-400米的精度。因此，对于深潜滑翔机，这种方法将使定位精度比目前的范例(即不频繁的GPS定位)提高10-100倍，并允许飞行器花更多的时间在深海进行相关观测。这项研究将使新的操作范例成为可能，提高观测能力，并促进比以前更密集的空间观测。此外，新系统还将提高估计平均深度洋流的能力。发展的能力也是多个深潜器协调运动控制的先决条件，进一步增加了深海观测的密度和节奏，提供了更加接近天气学的深海内部景象。开发的系统将首先在水箱中进行测试，然后在两次远洋航行中进行测试，包括在海滑器上进行第三年的部署。

Facilitating an accurately navigated persistent presence for the interior of the deep ocean has the potential to transform how oceanography is conducted. This capability is currently not provided by existing technologies; however, if developed would transform the scope of projects undertaken by underwater vehicles with longer range and endurance than can currently be deployed unsupported from research ships. This research develops a new low power navigation system that improves navigational accuracy from 1000s of meters to 100s meters. This advance will enable multiple new lines of oceanographic investigation. Examples include deployment of coordinated glider fleets to investigate complex physical-biogeochemical interactions; deep studies of topographically induced mixing; long-range characterization of seafloor habitats/ecosystems at the scale of entire ocean basins; and better resolution of the scales of bottom-boundary-layer processes in regions with steep underwater terrain. The researchers will engage in outreach activities including undergraduate participation in our research and continuation of established collaborations with local high school robotics and environmental science classes. This research develops and tests a low-power acoustic positioning system that enables accurate externally aided navigation in the deep ocean. A glider (or fleet of gliders) operates at depth while an autonomous surface robot (ASV) follows on the sea surface. The ASV transmits its geo-reference position to the gliders at a regular interval. Each glider then independently employs a precision time base (provided by chip-scale atomic clocks) and array processing to determine its position relative to the ASV. Each ASV combines this relative position estimate with the ASV's position encoded in the received packet to compute its geo-referenced position. System performance depends on a number of factors including the precision of vehicle attitude sensors. Accuracies of 250-400m are possible at 5000m depth using low-power sensors already in use on the glider. Hence, for deep-diving gliders, this method will provide a 10-100 fold improvement in positioning accuracy over the current paradigm (i.e., infrequent GPS fixes) and would allow vehicles to spend more time at depth making relevant observations. This research will enable new operating paradigms, advance observational capabilities and facilitate spatially denser observations than were previously possible. Furthermore, the new system will also improve the ability to estimate depth-averaged ocean currents. The developed capability is also a prerequisite for coordinated motion control of multiple deep-diving AUGs, further increasing the density and cadence of deep ocean observations, providing an ever closer-to-synoptic view of the deep ocean interior. The developed system will be tested first in the tank and then in two ocean cruises including a Year 3 deployment on a Seaglider.