R. Henthorn

A deliberative architecture for AUV control

Autonomous Underwater Vehicles (AUVs) are an increasingly important tool for oceanographic research demonstrating their capabilities to sample the water column in depths far beyond what humans are capable of visiting, and doing so routinely and cost-effectively. However, control of these platforms to date has relied on fixed sequences for execution of pre-planned actions limiting their effectiveness for measuring dynamic and episodic ocean phenomenon. In this paper we present an agent architecture developed to overcome this limitation through on-board planning using Constraint- based Reasoning. Preliminary versions of the architecture have been integrated and tested in simulation and at sea.

Mapping payload development for MBARI's Dorado-class AUVs

The Monterey Bay Aquarium Research Institute (MBARI) is developing an autonomous seafloor mapping capability for deep ocean science applications. The MBARI Mapping AUV is a 0.53 m (21 in) diameter, 5.1 m (16.7 ft) long, Dorado-class vehicle designed to carry four mapping sonars. The primary sensor is a 200 kHz multibeam sonar producing swath bathymetry and sidescan. In addition, the vehicle carries 100 kHz and 410 kHz chirp sidescan sonars, and a 2-16 kHz sweep chirp subbottom profiler. Navigation and attitude data are obtained from an inertial navigation system (INS) incorporating a ring laser gyro and a 300 kHz Doppler velocity log (DVL). The vehicle also includes acoustic modem, ultra-short baseline navigation, and long-baseline navigation systems. A single cylindrical pressure housing contains all of the mapping sonar electronics, and the main vehicle control and acoustic communications electronics are housed in a separate glass ball. The Mapping AUV is powered by three 2 kWhr Li-polymer batteries, providing an expected mission duration of 12 hours at a typical speed of 1.5 m/s. The assembled package is rated to 6000 m depth, allowing MBARI to conduct high-resolution mapping of the deep-ocean seafloor. Initial at-sea testing commenced in May 2004 using the subbottom profiler and 100 kHz sidescan. The sonar package will also be mountable on ROV Ventana, allowing surveys at altitudes < 10 m at topographically challenging sites. The MBARI Seafloor Mapping team is now working towards integration of the multibeam sonar and towards achieving regular operations during 2005.

Preliminary Results for Model-Based Adaptive Control of an Autonomous Underwater Vehicle

We discuss a novel autonomous system which integrates onboard deliberation with execution and probabilistic state estimation for an adaptive Autonomous Underwater Vehicle for deep sea exploration. The work is motivated by the need to have AUVs be goal-directed, perceptive, adaptive and robust in the context of dynamic and uncertain conditions. The challenges leading to deployment required dealing with modeling uncertainty and integrating control loops at different levels of abstraction and response for a dynamic environment. The system is general-purpose and adaptable to other ocean going and terrestrial platforms.

Ice profiling sonar for an AUV: experience in the Arctic

The harsh environment and limited resources available in the Arctic region make collection of most scientifically relevant data in the area difficult and/or expensive. The Monterey Bay Aquarium Research Institute (MBARI), along with other partners, has developed an autonomous underwater vehicle (AUV) specifically designed to withstand the difficult environment in the Arctic and capable of collecting a variety of scientific data. This tool has the potential to replace capabilities previously supported by the US Navy SCICEX cruises which used submarines for measuring and monitoring Arctic oceanographic properties. Scientific access to Navy submarines has been severely restricted over the last several years, with the future prospects for continued support uncertain. Ice draft data was one important piece of data historically collected by the submarines that MBARIs AUV now has the potential to provide. This ice draft data has particular value to climatologists and Arctic scientists who are striving to evaluate the impact of global climate on the thickness and extent of the Arctic ice sheet. This paper examines the ice draft data collected by the ALTEX AUV during its engineering test cruise in the Arctic in October 2001. A description of the experiments and the general performance of the vehicle are presented along with the scientific instrumentation layout of the AUV. Further, the modifications made to the ASL Environmental Sciences Ice Profiler/spl trade/ instrument to support vehicle operations in real-time are described. The use of this real-time data to drive vehicle decision making during missions is addressed as well. The data acquisition and processing techniques used to determine ice draft are then outlined, followed by samples of the ice draft data itself and estimates of its accuracy and repeatability. The conclusion include lessons learned and future plans for the ice profiling science payload.

MARS Benthic Rover: In-situ rapid proto-testing on the Monterey Accelerated Research System

The Benthic Rover is an autonomous, bottom-crawling vehicle being developed at the Monterey Bay Aquarium Research Institute (MBARI) to conduct long-term deep-ocean ecological research. In 2009 MBARI researchers deployed the Rover on the Monterey Accelerated Research System (MARS) cabled observatory for component and operational testing. MARS is located near-shore in the Monterey Bay near Monterey, CA, at a depth of approximately 900 meters, providing the power reliability and network accessibility similar to an on-shore laboratory. By enabling immediate feedback and the ability to quickly re-program control software and re-configure mission scripts, MARS facilitates a kind of “in-situ rapid proto-testing”. MBARI researchers were able to run numerous experimental procedures and analyze results in a relatively short timeframe, converging on desired operational profiles quickly and at very low cost. This paper will cover recent development work on the Benthic Rover with emphasis on the deployment and testing on MARS.

Initial Deployments of the Rover, an Autonomous Bottom-Transecting Instrument Platform for Long-Term Measurements in Deep Benthic Environments

Rover is a bottom-crawling, autonomous vehicle capable of making continuous time-series measurements at abyssal depths up to 6000 m for periods exceeding six months. The Rover control system and instrumentation suite are being designed at the Monterey Bay Aquarium Research Institute (MBARI), building on the earlier rover work of Smith and associates at the Scripps Institution of Oceanography. The vehicle weighs 68 kg in water and crawls on two wide tracks with a combined surface contact area of about one square meter; this provides good traction while minimizing the disturbance to benthic sediments. A typical mission scenario is to take measurements for a few days at each site before picking up the instruments and moving forward ~10 m to a new site. Up to fifty sites may be visited in a single mission. Engineering field tests have been performed with the Rover in the Monterey Bay in California (890 m depth), and at Station M, 220 km west of the central California coast (4200 m depth). Rover operations have been observed with the ROVs Ventana and Tiburon, and with the manned submersible DSV Alvin. Knowledge gained from these engineering deployments has resulted in numerous modifications and improvements to The Rover.

Precision underwater positioning for in situ laser Raman spectrographic applications

The Monterey Bay Aquarium Research Institute (MBARI) has developed and deployed a laser Raman spectrometer system (DORISS-Deep Ocean Raman In-Situ Spectrometer) for oceanic geo-chemical measurements of sea water specimens. Quality spectra have been obtained on standards carried to the seafloor. The next stage of this development involves the ability to obtain spectra from natural targets of interest in the deep ocean and to maximize signal return from the sample. To accomplish maximum signal return the DORISS probe head must be properly positioned and focused. In addition the probe head must be held steady for several minutes while spectra are being acquired. This is in contrast to laboratory work in which the sample is precisely positioned with respect to the probe head. This requirement has been the driver for a new device, the Precision Underwater Positioning system (PUP). The positioning system has strict requirements for motion about the target. The DORISS requires very exact and repeatable motions with positional accuracies in the <1 mm range over a large workspace. The device must also let the user see where they are focusing, be able to move without disturbing the base position, and to stay stable over a variety of terrains. In addition, the system must be adaptable to other vehicles. Another requirement is to return relative position from a known home position once the PUP is set in place. Moreover, the device has several operational constraints that impacted the design and operation of the system. This paper outlines the science drivers, the operational considerations, and the engineering trades that were made to build the first two stages of the PUP. The test results of this system are also included demonstrating the devices actual performance against the specifications. In conclusion the paper outlines the next tasks and the direction the program is taking to fulfill the complete precision underwater positioning system requirements.

Automating MBARI's midwater time-series video surveys: The transition from ROV to AUV

MBARI has been conducting remotely operated vehicle (ROV)-based video surveys of the upper 1000 meters of the water column in Monterey Bay, California for over 23 years. These surveys have produced a unique midwater time-series data set that has enabled MBARI scientists to observe changes in mesopelagic animal distribution and community structure in Monterey Bay over that time period. These changes can generally be associated with both short and long term changes in water mass structure, including some now being associated with climate change. This historical data set is becoming even more important as we begin to observe the effects of climate change on community structure and ecology in the midwater environment and try to predict the impact of future change. However, this data set comes at a high cost in ROV and support ship time required to conduct the surveys. In order to sustain these surveys into the future, a more cost effective approach is required. In an effort to reduce cost, improve methodology and develop a system that has the potential to be exported to other institutions, MBARI has developed a high definition video module to be deployed on its Dorado class autonomous underwater vehicle (AUV). This paper explores the challenges of this development, the chosen solutions, and presents early data derived from our initial inter-comparisons of video collected concurrently with MBARIs ROV and midwater imaging AUV.

Laser Raman spectroscopic instrumentation for in situ geochemical analyses in the deep ocean

Engineers and scientists at the Monterey Bay Aquarium Research Institute (MBARI) have successfully developed instrumentation for performing laser Raman spectroscopy in the deep ocean. Laser Raman spectroscopy is a form of vibrational spectroscopy that is capable of performing rapid, nondestructive, in situ geochemical analyses. The Deep Ocean Raman In Situ Spectrometer (DORISS) is based on a laboratory model laser Raman spectrometer from Kaiser optical systems, Inc. The sample is interrogated by a 532 nm laser and the Raman backscattered radiation passes through a holographic grating and is recorded on a CCD camera. Laser Raman spectroscopy is capable of analyzing a variety of solid, liquid and gaseous species. Due to the strict requirements for positioning the laser focal point when analyzing opaque samples, a Precision Underwater Positioning (PUP) system was built to position the DORISS probe head with respect to the sample. PUP is capable of translating the DORISS probe head in 0.1 mm increments with 1 mm repeatability. DORISS and PUP are deployed by MBARIs remotely operated vehicles - ROVs Tiburon and Ventana - and are controlled by a scientist aboard the surface ship. DORISS and PUP have been deployed a number of times in Monterey Bay, the Gulf of California, and Hydrate Ridge, Oregon for testing and analyses of natural targets of interest. The development of smaller, second generation systems will allow DORISS and PUP to be carried on other deep submergence vehicles for use by the wider oceanographic community.

Enabling new techniques in environmental assessment through multi-sensor hydrography

A suite of complementary survey tools aimed at producing 1-cm resolution bathymetric models co-registered with 2-mm pixel color photography has been assembled. The design goal is to produce quantitative documentation of both geological and biological features that will allow change over time to be assessed at vertical and lateral scales approaching one centimeter. The current suite of tools combines multibeam sonar, stereo cameras with dual xenon strobes, lidar, and an inertial navigation system (INS) aided by Doppler velocity log (DVL). This sensor package is mounted beneath remotely operated vehicles (ROV) and used to map the seafloor from low altitudes. A 100-m by 100-m survey can be accomplished in a single ROV dive. All surveys are conducted with scripted station-keeping control loops operating on the ROV, resulting in more efficient area coverage through tended automation. Fine scale surveys of a chemosynthetic biological community at 2850-m depth show that individual clams can be observed in both lidar bathymetry and photographic imagery. Repeat surveys over multiple years have been conducted in the morphologically active floor of Monterey Canyon. Comparison of these data resolve subtle transitions from depositional to erosional textures, and reveal the changes associated with frequent sediment transport events down the active canyon. The rocky, high relief environment of Sur Ridge offshore California hosts sponge and deep water coral habitats. Here the combination of acoustic and optic sensing proves particularly useful for quantitatively characterizing the benthic community. The multibeam sonar measures bathymetry without sensing soft animals, while the lidar measures a surface that includes these animals. Subtracting the multibeam bathymetry from the lidar bathymetry maps the locations and sizes of soft animals.