Showing papers on "iRobot Seaglider published in 2011"

Determining Vertical Water Velocities from Seaglider

Abstract: Vertical velocities in the world's oceans are typically small, less than 1 cm/s, posing a significant challenge to observation techniques. Seaglider, an autonomous profiling instrument, can be used to estimate vertical water velocity in the ocean to about half a centimeter per second. Using a Seaglider flight model and pressure observations, vertical water velocities are estimated along glider trajectories in the Labrador Sea before, during and after deep convection. Results indicate that vertical velocities in the stratified ocean agree with theoretical WKB-scaling of w, and in the turbulent mixed layer, scale with buoyancy and wind forcing. We estimate that accuracy is within 0.6 cm/s. Due to uncertainties in the flight model, velocities are poor near the surface and deep apogees, and during extended roll maneuvers. Some of this may be improved by using a dynamic flight model permitting acceleration, and by better constraining flight parameters through pilot choices during the mission.

Long-baseline acoustic localization of the Seaglider underwater glider

Abstract: This paper describes a long-baseline underwater acoustic localization system that was developed to provide three-dimensional position information for the Seaglider underwater vehicle The accurate inertial position of the glider can be used to estimate performance characteristics and to validate novel motion control and path planning strategies in future experiments The system consists of three acoustic transponders that are placed at known locations at the surface of the water An extended Kalman filter with RTS smoothing was used to obtain filtered estimates of the states The filtering methods have been tested both in simulations and in field experiments

Developing Tendency of Unmanned Underwater Vehicles

Abstract: With the fast pace of ocean exploitation,unmanned underwater vehicles,as the most important means of ocean exploration for human,gained unprecedented attention and development.In this article,the definition and classification of the unmanned underwater vehicles are given.The current status and developing tendency of unmanned underwater vehicles in recent years are introduced, and the key technologies and future development direction of autonomous underwater vehicle are analyzed.

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.

Physical oceanographic data from Seaglider trials in stratified coastal waters using a new pumped payload CTD

Abstract: The Seaglider, developed by the University of Washington with ONR (Office of Naval Research) funding and licensed to iRobot in 2008, is an autonomous underwater vehicle used for a wide variety of occeanographic research. Science payloads installed on gliders typically include temperature (T) and conductivity (C) sensors, or a CTD (Conductivity-Temperature-with-Depth profiler), in which the T and C measurements are used to derive salinity, density and other important physical parameters. Free-flushed CTDs by Sea-Bird Electronics, referred to here as the CT Sail, were the first science payload installed in the Seaglider. While these are still in use on many Seagliders, they are being phased out in favor of a modular, low-power pumped CTD, referred to as the GPCTD (Glider Payload CTD), also by Sea-Bird Electronics. Data gathered during field trials of the Seaglider integrated with the new GPCTD alongside Seagliders with the free-flushed CT Sails offer an opportunity to evaluate and compare the data quality between the two CTD types. Data provided by iRobot come from June 2011 mission trials conducted in the stratified waters along the coast off Massachusetts. Comparisons of dive profiles made simultaneously by pairs of Seagliders indicate the raw pumped GPCTD data show improved data quality with less salinity spiking and conductivity cell thermal mass errors compared to the free-flushed CT Sail data. Applying consistent corrections to the GPCTD data for sensor measurement alignment and time-dependent conductivity cell thermal mass errors further improves accuracy. Corrections to GPCTD data are simple in comparison to the unpumped CT Sail data, because the GPCTD pumped flow produces a steady T-C sensor response, and the GPCTD data acquisition system provides a constant sample-rate time series necessary for these time-dependent corrections.

An Overview of Autonomous Underwater Vehicle Systems and Sensors at Georgia Tech

Abstract: As the ocean attracts great attention on environmental issues and resources as well as scientific and military tasks, the need for the use of underwater vehicle systems has become more apparent. Underwater vehicles represent a fast-growing research area and promising industry as advanced technologies in various subsystems develop and potential application areas are explored. Great efforts have been made in developing autonomous underwater vehicles (AUVs) to overcome challenging scientific and engineering problems caused by the unstructured and hazardous ocean environment. With the development of new materials, advanced computing and sensory technology, as well as theoretical advancements, research and development activities in the AUV community have increased.

Passive‐acoustic monitoring of odontocetes using a Seaglider: First results of a field test in Hawaiian waters.

Abstract: In fall 2009 the University of Washington, Applied Physics Laboratory conducted in collaboration with the Oregon State University, a comprehensive field test of a passive‐acoustic Seaglider along the western shelf‐break of the island of Hawaii. During the 3 week mission, a total of approximately 170 h of broadband acoustic data [194 kHz sampling rate] were collected. The recordings were manually analyzed by an experienced analyst for beaked whale (Ziphiidae), dolphin (Delphinidae), and sperm whale (Physeter macrocephalus) echolocation clicks as well as echo sounder pings emitted by boats in the area. Here we present and discuss first results of these data analysis, which revealed that more than 50% of the recorded files (each of 1‐minute duration) contain bioacoustic signals. Furthermore the recorded data and the results of the manual analysis are used to validate and optimize an automated classifier for odontocete echolocation clicks, which was developed in a collaborative effort with San Diego State Uni...

Automatic Detection of Beaked Whales from Acoustic Seagliders & Passive Autonomous Acoustic Monitoring of Marine Mammals with Seagliders

Abstract: : The U.S. Navy's use of tactical mid-frequency active sonar has been linked to marine mammal strandings and fatalities (NMFS 2001). These events have generated legal challenges to the Navy's peacetime use of mid-frequency sonar, and have limited the Navy's at-sea anti-submarine warfare training time. Beaked whales may be particularly sensitive to mid-frequency sonar. A mobile, persistent surveillance system that could detect, classify and localize beaked whales will help resolve the conflict between the Navy's need for realistic training of mid-frequency sonar operators and the Navy s desire to protect marine mammal populations worldwide. Underwater gliders equipped with appropriate acoustic sensors, processing, and detection systems passive acoustic monitoring (PAM) gliders may offer a partial solution to the problem. The acoustically-equipped Seaglider from the Applied Physics Laboratory of the University of Washington (APL-UW) is one such platform. A Seaglider can travel about 20 km/day through the water for a period of weeks to months, dive from the surface to 1000 m and back in a few hours, and use two-way satellite (Iridium) telemetry for data and command transfer. This makes it potentially highly useful for the long-term goal of this project, mitigating impacts of Navy operations on marine mammals.

Vehicle for Automation Research and Underwater Navigation

Abstract: Vehicle for Automation Research and Underwater Navigation, VARUN is an autonomous underwater vehicle designed and developed by undergraduate students of Delhi Technological University, New Delhi. It is designed with a focus on shallow water applications in defense such as mine countermeasures, surveillance and reconnaissance and civilian applications at ports, in ship maintenance and in marine research. The development of the vehicle involves a multi-disciplinary approach with engineers from electronics, mechanical, information technology and production engineering.

Hydrodynamic characteristics of the main parts of a hybrid-driven underwater glider PETREL

Abstract: As a special type of AUV, underwater gliders have many advantages, such as long endurance, low noise and low energy cost. A glider can periodically change its net buoyancy by a hydraulic pump, and utilize the lift from its wings to generate forward motion. The inherent characteristics of a glider can be summarized as buoyancy-driven propulsion, sawtooth pathway, high endurance and slow speed. There exist three legacy gliders named respectively Seaglider, Spray and Slocum [1~6]. In spite that underwater gliders features low level of self noise and high endurance, they also have weaknesses like the lack of maneuverability and the inability to perform a fixed depth or level flight [7]. Driven by a propeller with carried energy source, autonomous underwater vehicles is preprogrammed to carry out an underwater mission without assistance from an operator on the surface. However, they can only cover a relatively short range after each recharge due to the high power consumed for propulsion and generate much more noise than the AUGs because of its propeller and motors [8~10]. The range of AUV’s is restricted by the amount of energy carried on board, can was not more than several hundreds kilometers in general [11]. The performances of the underwater vehicle are compared in Figure 2.

Overview of the development and advantages of new, larger fairings for the iRobot Seaglider

Abstract: iRobot has developed a new, larger set of fairings for Seaglider. The design of the new fairing significantly increases Seaglider's volume and mass payload capabilities while reducing total drag on the vehicle. Payload volume is increased by 6.5 times and payload mass is doubled over the original design. Development over the course of a year involved computational fluid dynamic (CFD) analysis, prototyping, and ocean testing to arrive at an optimized design solution.

Autonomous Underwater Vehicle Sampling System

Abstract: : The long-term goal of this project is to acquire a deep-diving autonomous underwater vehicle (AUV) for community use.

The Yellowfin Autonomous Underwater Vehicle Acoustic Communication Design and Testing

Abstract: Over the past two years, the Georgia Tech Research Institute (GTRI) has developed a new Unmanned Underwater Vehicle (UUV) called the Yellowfin. The purpose of the vehicle is to provide a platform for research and development of autonomous, multivehicle underwater technology. This paper documents the design of the vehicle with an emphasis on the acoustic communication system, including the hardware and software. The testing of the ACOMMS hardware and software system is also discussed.