R. Stokey

REMUS: a small, low cost AUV; system description, field trials and performance results

A new generation of autonomous underwater vehicles are being successfully utilized to support a number of scientific and military objectives. Despite their small size and low cost, these new vehicles are versatile, reliable and require only a two person support staff. These features make the vehicles affordable and available for use by a broad segment of the oceanographic community. The vehicle operators must be confident that they can cost effectively use these new tools with a minimum of support staff for missions such as coastal ocean surveys, and pollution identification and source tracking. An effort to design and fabricate a low cost, small, and accessible vehicle resulted in REMUS, Remote Environmental Measuring UnitS. The vehicle is 19 cm in diameter by 134 cm long and weighs 31 kg. It has an operating and control system based on the PC-104 form factor of the IBM-PC which can be connected to a laptop computer for system configuration. With 400 watt-hours of conventional lead acid batteries the vehicle has a useful range of 25 nautical miles at 3 knots, and a top speed of 5 knots. REMUS is capable of navigating itself using a variety of techniques including long and ultra-short baseline acoustic navigation, bottomlock Doppler navigation and GPS reception. The major system design features are described in this paper including the electrical power plant, the vehicle control system, the acoustic navigation system, and the user interface to the vehicle. The mechanical design and system performance are presented along with recent results from field tests of navigating the vehicle around a pair of transponders.

Remote environmental measuring units

There are civilian and military justifications for the development and commercialization of free swimming survey platforms which may be carried and operated by one person. To be effective, these platforms must be capable of characterizing the spatial and vertical variability of the physical environment beneath the surface of the water. There is therefore a need to develop low risk, affordable, underwater vehicles which are easily reproduced and which provide effective solutions, but whose loss is not an economic catastrophe. Research aimed at quantifying cause and effect relationships and predicting long term trends in coastal, inland and global marine processes will benefit from such systems. One important aspect of such research is the development of coastal ocean modeling and data assimilation computer programs which permit hind-casting and forecasting of circulation patterns in coastal regions. An affordable system of vehicles, which will permit ground truthing of remotely sensed data and the rapid measurement of vertical distributions beneath the surface, will support the use of these computer programs in characterizing remote coastal regions with a minimum investment. Once operational, these models may be used in support of both military and civilian objectives. A system of remote environmental measuring unit(s) (REMUS) is intended to provide such a capability. The REMUS concept includes a number of small, low cost, free swimming vehicles which may be operated jointly or independently. They offer an appropriate technology for gathering data in the coastal and open ocean. Operations in the open ocean may be conducted from large or small ships of opportunity as well as from long term seafloor observatories such as Rutgers LEO-15, which operates at the end of an electro-optic cable buried in the seafloor. Coastal and inland, operations may be conducted from a shore station or a pier side location, as well as from a small boat. Since the vehicle weight will not normally exceed 40 kilograms, it is envisioned that the vehicle system may be transported to the site of interest in a compact car and set up and operated by one person.

Remote Environmental Monitoring Units: An Autonomous Vehicle for Characterizing Coastal Environments*

Abstract In oceanography, there has been a growing emphasis on coastal regions, partially because of their inherent complexity, as well as the increasing acknowledgment of anthropogenic impacts. To improve understanding and characterization of coastal dynamics, there has been significant effort devoted to the development of autonomous systems that sample the ocean on relevant scales. Autonomous underwater vehicles (AUVs) are especially well suited for studies of the coastal ocean because they are able to provide near-synoptic spatial observations. These sampling platforms are beginning to transition from the engineering groups that developed and continue to improve them to the science user. With this transition comes novel applications of these vehicles to address new questions in coastal oceanography. Here, the relatively mature Remote Environmental Monitoring Units (REMUS) AUV system is described and assessed. Analysis of data, based on 37 missions and nearly 800 km of in-water operation, shows that the...

Autonomous Docking Demonstrations with Enhanced REMUS Technology

As autonomous underwater vehicles (AUVs) become more pervasive and enter common usage, systems that expand their capabilities, extend their range, and/or permit operation in denied areas become essential. A dock is one method of achieving these goals. An autonomous dock for an AUV provides the capability to greatly increase the duration and extent of AUV operations, provided the dock has a substantially greater energy supply than the AUV. Other docking station applications include the possibility of installation onto a cabled Oceanographic observatory, thus providing unlimited power for battery recharge and continuous data communications. This paper presents the design, development, testing, and results of recent field demonstrations of a compact bottom-mounted docking station for a modified REMUS-100 series AUV. In addition to the dock development, the REMUS vehicle was enhanced with a new, modular endcap to facilitate the installation of modular sensors to the vehicle for the docking program. These sensors include a new digital ultra-short baseline (USBL) acoustic homing array and a periscope camera for sea-surface observations. The USBL homing array along with DVL velocity and altitude information provided the capability of the AUV to reliably navigate along a preprogrammed glidepath into an entrance nozzle of the dock. A unique challenge of this second generation docking system was the requirement for small size and near-bottom entrance into the dock

Development of the REMUS 600 autonomous underwater vehicle

The Oceanographic Systems Laboratory of the Woods Hole Oceanographic Institution has developed the REMUS 600, a new 12.75 inch (32.385 cm) diameter autonomous underwater vehicle that will be used to carry mine countermeasures sensors for the Office of Naval Research. Vehicle Control Technologies has been tasked by ONR to develop autopilot and simulation software for several REMUS 600 sensor configurations, with the objective of achieving enhanced platform steadiness to improve sensor performance in the shallow water and very shallow water environment. The most stringent motion steadiness requirements for the REMUS 600 vehicle are derived from the image forming specifications of a new side-looking synthetic aperture sonar developed for ONR by the Penn State Applied Physics Laboratory and the Coastal Systems Station, Panama City, Florida. This payload necessitated the use of a forward fin section for enhanced control authority. This forward fin section gives the vehicle the ability to command vertical and horizontal sideslips, in addition to roll, pitch, and yaw control, using independently commanded fins. This is a unique capability for a vehicle of this class. In addition, the 12.75 inch diameter vehicle class offers new capabilities for endurance and payload capacity. The REMUS 600 software architecture has been designed with the flexibility to accommodate various payloads and both the VCT autopilot and the Woods Hole autopilot. We present the VCT approach to autopilot design which makes use of a high-fidelity hydrodynamics model, software in the loop simulation test, vehicle motion steadiness performance predictions, and post-test validation. The REMUS 600 vehicle has collected extensive in-water data. We present performance results based on this data

A docking system for REMUS, an autonomous underwater vehicle

The future of autonomous underwater vehicles (AUVs) lies in making them affordable and easy to use. Ease of use must encompass not just the man-machine interface to the vehicle, but also address the requirements for vehicle launch and recovery. As long as ships and crews must be mobilized for each AUV mission, their utility will be limited. Development of a docking capability will allow these vehicles to remain on station as part of an autonomous ocean sampling network. This paper describes the docking system developed for REMUS (Remote Environmental Monitoring UnitS), a low cost AUV designed by the Oceanographic Systems Laboratory at the Woods Hole Oceanographic Institution. The paper discusses the solutions developed for enabling the vehicle to acoustically find and then home on the docking system; mechanically latching the vehicle to the dock; electro-mechanical techniques for power and data transfer from the docking system to the vehicle; remote data download from the vehicle and mission upload to the vehicle; and in situ battery recharge without opening the vehicle housing. Results from successful tests of the system are discussed.

A Compact Control Language for AUV acoustic communication

Acoustic communication with autonomous underwater vehicles (AUVs) implies low data rates and potentially high latency, depending on the range and the number of vehicles operating in one area. To efficiently use this limited resource the Compact Control Language (CCL) was developed for use with the WHOI REMUS AUV. CCL is a set of messages that includes commands for AUVs and data messages for typical sensors. Almost all of the messages are less than 32 bytes long. CCL commands include simple operations such as Abort Now and Abort to Mission End, but also complex commands such as re-direction with side scan sonar over areas of interest. When this simple command set is used with a telemetry system that includes network addressing (such as the WHOI Micro-Modem), sophisticated multi-vehicle operations may be carried out. The open nature of the specification allows vehicles developed at different research institutions or commercial companies to work together, thus promoting interoperability. CCL has been adopted by others working in the Office of Naval Research Very Shallow Water mine-countermeasure (VSW-MCM) program which includes multiple vehicles with different types of sensors.

Enabling technologies for REMUS docking: an integral component of an autonomous ocean-sampling network

A dock for an autonomous underwater vehicle (AUV) allows the vehicle to be left on station ready for deployment. However, it represents a significant engineering challenge, as docking requires an accurate navigation system so that the vehicle can find the dock, and complex mechanics to make the required underwater power and data connections. This paper describes the docking system built for the REMUS AUV. It outlines the basis for the design decisions, the as-built configuration, and its performance once deployed. It also delineates the lessons learned from the deployments, and the refinements in the vehicle that have been made since that time, that will improve the systems utility and reliability.

Under-ice operations with a REMUS-100 AUV in the Arctic

Use of a REMUS-100 AUV to obtain hydrographic observations beneath coastal sea ice offshore of Barrow, Alaska is described. The work is motivated by the desire to obtain cross-shore hydrographic transects that would provide estimates of the transport of relatively dense, salty water from the Chukchi Sea to the Arctic Ocean in winter. The horizontal scales (∼10 km), maximum water depths (∼100 m) and desired measurements (temperature, salinity and velocity vs. depth) in the study region match the capabilities of a small AUV such as the REMUS-100. It was recognized that achieving the science goals would require increasing the range of acoustic navigation and communication as well as developing a robust approach to through-ice deployment and recovery. These needs drove three modifications to the AUV: 1) Incorporation of a lower frequency (10 kHz) transducer and associated hardware for navigation and communication, 2) Addition of special-purpose sensors and hardware in a hull extension module, 3) Development of a homing algorithm utilizing an Ultra-Short Base Line (USBL) array in the AUV nose cap. In March 2010, eight days of field work offshore of Barrow provided successful demonstration of the system. A total of 14 km of track lines beneath a coastal ice floe were obtained from four missions, each successfully terminated by net-capture recovery.

Autonomous Underwater Vehicle Operations Beneath Coastal Sea Ice

Use of an autonomous underwater vehicle (AUV) to obtain environmental observations beneath coastal sea ice offshore of Barrow, AK, is described. This study is motivated by the desire to obtain cross-shore hydrographic transects (temperature, salinity, and velocity versus depth) that would provide estimates of the transport of relatively dense, salty water from the Chukchi Sea to the Arctic Ocean in winter. Although person-portable AUVs are well suited to the task, it was recognized that achieving the science goals would require increasing the range of acoustic navigation and communication as well as developing a robust approach to through ice deployment and recovery. These needs drove three modifications to the AUV: 1) incorporation of a lower frequency (10 kHz) transponder and associated hardware for navigation and communication; 2) addition of special-purpose sensors and hard- ware in a hull extension module; and 3) development of a homing algorithm utilizing Ultrashort Base Line acoustics. In March 2010, eight days of field work offshore of Barrow provided successful demonstration of the system. A total of 14 km of track lines be- neath a coastal ice floe were obtained from four missions, each successfully terminated by net-capture recovery.