C. von Alt

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.

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.

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.

Leo-15 An Unmanned Long Term Environmental Observatory

This paper presents a concept which invcilves the instal- lation of a series of instrumented seafloor platforms which are linked to shore by an electro-optic cable. The use of an electro-optic cable permits these ocean-based systems to gather data continuously, for a long period of time, and at extended distances from shore. A system life time exceeding 20 years is possible. The electro-optic cable will transfer continuous electrical power and will provide a means of establishing a broad bandwidth fiber-optic link to the seafloor sys- tems. The use of a broad bandwidth bi-directional fiber-optic link facilitates real time interactive control of ocean based experiments, instrumentation, and tethered and free swimming vehicle systems. Once data and control links are transferred to the shore station over the fiber-optic channel, they may then be made accessible for use in world wide education and research programs, through1 modem com- puting and communication technologies. Specifically, thii paper examines the design and installation of a Long Term Environmental Observatory which will be operated in 15 meters of water (LEO-15). LEO-I5 will be located approximately 9 kilometers off the New Jersey Coast at Little Egg Inlet. The observa- tory will be linked to Rutgers, The State University of New Jersey, Institute of Marine and Coastal Sciences shore station at Tuckerton by an electro-optic cable which will be buried in the seafloor. It has been determined that with some routine maintenance, a reli- able long term system may be developed and put into operation. The successful installation and operation of the LEO-I5 fzrcility should provide the engineering experience and scientific motivation neces- sary to install additional observatories, worldwide, in both coastal and deep water sites. order to understand the processes governing stability and change in the ocean, there is a need to make observations, in situ, over long periods of time. The ability to obtam experi- mental data, in real time, and to control and redirect undersea experiments, from a shore based laboratory, based on this real time data, will greatly enhance the quality of the data col- lected.

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.

RATS, a Relative Acoustic Tracking System developed for deep ocean navigation

Long baseline (LBL) acoustic navigation techniques have traditionally been used to find the position of vehicles or towed systems in the deep ocean. LBL techniques compute the vehicle position by triangulation, based on measured acoustic ranges to fixed acoustic transponders. There is a considerable motivation to develop an accurate relative navigation system, whereby the subsea vehicle position may be calculated with respect to the surface ship, based on a range and bearing measurement, thus eliminating the need for bottom transponders. The vehicles position may then be found in world coordinates, by adding the relative position of the vehicle to the GPS position found for the ship. The errors associated with relative navigation are primarily angular in nature, thus making it difficult to achieve sufficient accuracy at long ranges to satisfy the survey requirements. This paper describes RATS (Relative Acoustic Tracking System), which was developed by the Woods Hole Oceanographic Institution specifically for determining the position of the TOSS deep towed imaging vehicle system, operated by the Naval Oceanographic Office. RATS utilizes wide band signaling techniques with DSP (digital signal processor) implementation, combined with six axis motion compensation to obtain high accuracy relative positioning of the towed system with respect to the surface ship. A complete description of the system, as well as field results from deep ocean operations, is presented.

The LEO-15 Long-term Ecosystem Observatory: design and installation

The Long-term Ecosystem Observatory (LEO-15) provides scientists with power and telemetry for instruments deployed off the central coast of New Jersey for the Institute of Marine and Coastal Sciences at Rutgers University. The ability to read and control a deployed instrument in real-time allows a researcher to modify experiments or to respond to events of interest as they occur. The observatory provides two nodes deployed in about 15 m depth with diver accessible connectors for guest instruments. The nodes are connected to a shore station through a 9-km, buried, electro-optic cable. The cable power wires and optical fibers are connected between a node base and a node instrument frame via diver mateable connections. This permits the instrument frame to be easily removed for repair or periodic maintenance. The node bases are designed and anchored to withstand anticipated storms that occur in this coastal area. Various means have been employed to limit corrosion and bio-fouling. Each node provides a vertical profiler for making a variety of oceanographic measurements from a buoyant frame attached to a winch deployed cable. Additional guest instruments can connect to one of eight standard ports, or to one of several specialized interfaces. The telemetry system provides unbuffered serial data connections at various speeds between a users instrument(s) and shore equipment. One video channel is also available from each node. Power and data wires for each instrument are switched under the direction of a computer in the shore station. This computer monitors the instruments for various faults, can disconnect faulted instruments, and will send notification to operators and scientists when problems occur. Several means are provided for a user to request the central computer to turn an instrument on or off, or to report an instruments status.

The Martha's Vineyard Coastal Observatory: a long term facility for monitoring air-sea processes

The desire to gain a better understanding of coastal processes over the past decade has led to an increased focus on coastal research in the scientific community. As an estimated 50% of humanity lives within 100 miles of a coastline and as national defense initiatives shift towards littoral regions, this interest in coastal processes will continue to grow. The south shore of the island of Marthas Vineyard is an ideal location for the study of the near-shore environment, due to its uninterrupted, south-facing beach with open ocean exposure. This area is frequented by all types of weather systems, including winter storms, hurricanes, and calm summer conditions. The seasonal variations provide a wide range of biological activity as well. To support long-term research in these areas, the Woods Hole Oceanographic Institution (WHOI), supported by the National Science Foundation, is currently developing and installing a coastal observatory system on the south shore of the Vineyard in Edgartown, Massachusetts.