iRobot Seaglider

About: iRobot Seaglider is a research topic. Over the lifetime, 176 publications have been published within this topic receiving 3279 citations.

A Seaglider-Integrated Digital Monitor for Bioacoustic Sensing

Abstract: An acoustic Digital MONitor (DMON) has been integrated into a Seaglider autonomous underwater vehicle to serve as a general-use tool for passive acoustic sensing of marine mammal vocalizations. The system is being developed as a complement to conventional ship-based cetacean survey methods. The acoustic system includes three omnidirectional hydrophones, one located on centerline of the aft payload hatch and one on each wingtip. An onboard real-time detector has been implemented to record an audio sample if ambient noise has risen above a user-prescribed signal-to-noise ratio (SNR) threshold level. The data size and the number of detections are available in semi-real time, and the acoustic data are retrieved upon recovery of the instrument. Because the DMON system interfaces with the Seaglider firmware, the glider pilot has the capability to modify several operational parameters governing the collection of acoustic data while the glider is deployed to tailor the data recording to the desired mission objectives. This implementation is referred to as the Seaglider Customizable Sampling Configuration (SCSC) DMON and has recorded a wide variety of cetacean vocal activity offshore the Hawaiian Islands.

Development of a Hovering-Type Intelligent Autonomous Underwater Vehicle, P-SURO

Abstract: P-SURO(PIRO-Smart Underwater RObot) is a hovering-type test-bed autonomous underwater vehicle (AUV) for developing various underwater core technologies (Li et al., 2010). Compared to the relatively mature torpedo-type AUV technologies (Prestero, 2001; Marthiniussen et al., 2004), few commercial hovering-type AUVs have been presented so far. This is partly because some of underwater missions of hovering-type AUV can be carried out through ROV (Remotely Operated Vehicle) system. But the most important reason is of less mature core technologies for hovering-type AUVs. To carry out its underwater task, hovering-type AUV may need capable of accurate underwater localization, obstacle avoidance, flexible manoeuvrability, and so on. On the other hand, because of limitation of present underwater communication bandwidth, high autonomy of an AUV has become one of basic function for hovering AUVs (Li et al., 2010). As a test-bed AUV, P-SURO has been constructed to develop various underwater core technologies, such as underwater vision, SLAM, and vehicle guidance & control. There are four thrusters mounted to steer the vehicle's underwater motion: two vertical thrusters for up/down in the vertical plane, and 3DOF horizontal motion is controlled by two horizontal ones, see Fig. 1. Three communication channels are designed between the vehicle and the surface control unit. Ethernet cable is used in the early steps of development and program/file upload and download. On the surface, RF channel is used to exchange information and user commands, while acoustic channel (ATM: Acoustic Telemetry Modem) is used in the under water. A colour camera is mounted at the vehicle's nose. And three range sonar, each of forward, backward and downward, are designed to assist vehicle's navigation as well as obstacle avoidance and SLAM. An AHRS combined with 1axis Gyro, 1-axis accelerometer, depth sensor consist of vehicle's navigation system. In this chapter, we report the details of to date development of the vehicle, including SLAM, obstacle detection/path planning, and some of vehicle control algorithms. The remainder of this chapter is organized as follows. In Section II, we introduce the vehicle's general specifications and some of its features. Underwater vision for P-SURO AUV is discussed in Section III, and the SLAM algorithm in the basin environment is presented in Section IV. In Section V, we discuss some of control issues for P-SURO AUV. Finally in Section VI, we make a brief summary of the report and some future research issues are also discussed.

Hydrographic observations of oxygen and related physical variables in the North Sea and western Ross Sea polynya : investigations using seagliders, historical observations and numerical modelling

Abstract: Shelf seas are one of the most ecologically and economically important ecosystems of the planet. Dissolved oxygen in particular is of critical importance to maintaining a healthy and stable biological community. This work investigates the physical, chemical and biological drivers of summer oxygen variability in the North Sea (Europe) and Ross Sea polynya (Antarctica). In particular, this work also focuses on the use of new autonomous underwater vehicles, Seagliders, for oceanographic observations of fine scale (a few metres) to basin-wide features (hundreds of kilometres). Two hydrographic surveys in 2010 and 2011 and an analysis of historical data dating back to 1902 revealed low dissolved oxygen in the bottom mixed layer of the central North Sea.We deployed a Seaglider in a region of known low oxygen during August 2011 to investigate the processes regulating supply and consumption of dissolved oxygen below the pycnocline. Historical data highlighted an increase in seasonal oxygen depletion and a warming over the past 20 years. Regions showing sub-saturation oxygen concentrations were identified in the central and northern North Sea post-1990 where previously no depletion was identified. Low dissolved oxygen was apparent in regions characterised by low advection, high stratification, elevated organic matter production from the spring bloom and a deep chlorophyll maximum. The constant consumption of oxygen for the remineralisation of the matter exported below the thermocline exceeded the supply from horizontal advection or vertical diffusion. The Seaglider identified cross-pycnocline mixing features responsible for reoxygenation of the bottom mixed layer not currently resolved by models of the North Sea. Using the data, we were also able to constrain the relative importance of different sources of organic matter leading to oxygen consumption. iii From November 2010 to February 2011, two Seagliders were deployed in the Ross polynya to observe the initiation and evolution of the spring bloom. Seagliders were a novel and effective tool to bypass the sampling difficulties caused by the presence of ice and the remoteness of the region, in particular they were able to obtain data in the polynya before access was possible by oceanographic vessels. Seagliders were able to survey the region at a fraction of the cost and inconvenience of traditional ship surveys and moorings. We present observations of a large phytoplankton bloom in the Ross Sea polynya, export of organic matter and related fluctuations in dissolved oxygen concentrations. The bloom was found to be widespread and unrelated to the presence of Ross Bank. Increased fluorescence was identified through the use of satellite ocean colour data and is likely related to the intrusion of modified circumpolar deep water. In parallel, changes in dissolved oxygen concentration are quantified and highlight the importance of a deep chlorophyll maximum as a driver of primary production in the Ross Sea polynya. Both the variability of the biological features and the inherent difficulties in observing these features using other means are highlighted by the analysis of Seaglider data. The Seaglider proved to be an excellent tool for monitoring shelf sea processes despite challenges to Seaglider deployments posed by the ice presence, high tidal velocities, shallow bathymetry and lack of accurate means of calibration. Data collected show great potential for improving biogeochemical models by providing means to obtain novel oceanographic observations along and across a range of scales.