B. Allen

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.

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.

Hunting for mines with REMUS: a high performance, affordable, free swimming underwater robot

Over the past five years, Remote Environmental Measuring Unit(s) (REMUS) [1] has proven itself to be a reliable and affordable means of performing minefield and hydrographic reconnaissance missions in very shallow water (3 to 12 in depths) and in shallow water (12-30 in depths). Navy sponsored field evaluations and participation in Naval Fleet Battle Experiments, sponsored by ONR, have demonstrated that fleet personnel can successfully operate the system and that it has significant logistical advantages over traditional diver operated, marine mammal, and larger vehicle systems. The advantages of REMUS include the ease of planning and executing operations, its high area coverage rate, its endurance, and an overall reduction in logistical issues due to the systems small size and inherent portability. In addition, REMUS systems provide a complete solution, from mission planning and execution to post-mission analysis, including the generation of reports that aid in decision making at the command level. Navy personnel who have been trained in the operation of REMUS quickly gain confidence in programming, maintaining, and operating the system; they are often ready to take the system on an operation within days of seeing REMUS for the first time. REMUS has also demonstrated its compatibility with MEDAL during two fleet battle experiments. The capabilities of REMUS have drawn interest from many Navies throughout the world. Consideration of existing and future Naval requirements and the demonstrated capabilities of the system indicate that there is an even greater scope of missions that a REMUS system may be used for in the future. This paper reviews emerging requirements and the demonstrated capabilities of REMUS.

New capabilities of the REMUS autonomous underwater vehicle

Autonomous underwater vehicle technology continues to advance at a rapid pace. REMUS (Remote Environmental Monitoring UnitS), developed by the Oceanographic Systems Laboratory at the Woods Hole Oceanographic Institution, is one of the most widely used autonomous underwater vehicles in the world. Each year REMUS vehicles participate in numerous field exercises in support of scientific and navy research objectives. Designed for coastal operations, REMUS is normally deployed with a CTD, light scattering sensor, side scan sonar and an up-and-down looking acoustic doppler current profiler (ADCP). Additional sensors are easily integrated in the vehicle and a bioluminescence instrument and a turbulence sensor package. Recent development efforts have improved the REMUS vehicle overall design and performance, and include integration of two new sensors. Vehicle improvements include lower drag, a new propulsion, new lithium-ion batteries and a new external interface. Maximum speed has been increased from 1.75 m/s to almost 3 m/s (6 knots) and mission length has increased to 22 hours at the 1.5 m/s (3 knots) cruising speed. REMUS has been used to demonstrate a new autonomous underwater vehicle application: plume mapping. A rhodamine fluorometer was installed to map a plume on a steep sloping sea floor. Results from the field test demonstrate the effectiveness of an AUV as a tool in this task. A second REMUS vehicle has been deployed with an optical sensor package. The instruments in the package include a chlorophyll fluorometer and up-and-down looking, seven channel radiometers. This package combined with the standard CTD and ADCP generates a significant scientific data set, which supports both physical and biological oceanographic research.

Propulsion system performance enhancements on REMUS AUVs

This paper details recent efforts on drag reduction, vehicle shape and propulsion system modifications, and propeller design for the REMUS class of autonomous underwater vehicles (AUV). Drag reduction was accomplished by tow-tank measurements of an existing design to itemize the sources of drag. The vehicle shape and main propulsion system were modified to use magnetic torque transfer through a seawater collar to eliminate a rotating shaft seal. Propeller design efforts consisted first of a trade-off analysis of blade number, RPM, vehicle speed and blade shape to determine an optimum design and then refinement of that design for production version. The combined effect of these efforts resulted in a four fold reduction in propulsion power at the same speed of the previous design, and an increase in maximum achievable speed by almost a factor of two. These propulsion system performance improvements combined with recent changes in energy capacity for the vehicle result in a total per mission range of 120 km at 1.5 m/s for an endurance of 20 hours.