A highly versatile autonomous underwater vehicle with biomechanical propulsion

In this chapter, the receding horizon Kalman filter is applied to underwater navigation systems. The ocean covers about two-thirds of the earth and has a great effect on human beings. However, the ocean is overlooked while we focus our attention on land and atmospheric issues; we have not been able to explore the full depths of the ocean, its abundant livings and non-living resources. For example, only recently we have discovered, by using manned submersibles, that a large amount of methane and carbon dioxide comes from the seafloor and extraordinary groups of organisms live in hydrothermal vent areas. However, a number of complex issues due to the unstructured and hazardous undersea environment make it difficult to survey in the ocean even though today’s technologies have allowed humans to land on the moon and robots to travel to Mars. Unmanned underwater vehicles (UUVs) can help us better understand marine and other environmental issues, protect the ocean resources of the earth from pollution, and efficiently utilize them for human welfare. The UUV is a platform for a variety of sensors: acoustic, magnetic, gravimetric and chemical ones. Most commercial UUVs are tethered and remotely operated, referred to as remotely operated vehicles (ROVs). Extensive use of manned submersibles and ROVs are currently limited to a few applications because of very high operational costs, operator fatigue and safety issues. The demand for advanced underwater vehicle technologies is growing and will eventually lead to fully autonomous and reliable underwater vehicles. Autonomous underwater vehicles (AUVs) were initially developed to perform missions that were not easy for ROVs and manned underwater vehicles. Since the autonomy allows AUVs to be used for risky missions such as a mine countermeasure (MCM) or under-ice operations, AUVs are replacing ROVs towed vehicles as well as manned underwater vehicles (Whitcomb, 2000). For detailed ocean surveys, an AUV acts as a more stable platform for precision sensors than ROVs or towed vehicles because an AUV is not subject to physical disturbances transmitted along the cable to the surface vessel. This absence of physical attachment also allows AUVs to measure ocean characteristics at specific depths and perform bottom-following missions as owing to its autonomy. In short, An AUV provides marine researchers with a new form of access to deeper ocean. For an AUV to successfully complete a typical survey mission, it must follow a path specified by the operator as closely as possible and arrive at a precise location for collecting data. When an AUV is not able to follow the path accurately during the mission, critical Source: Kalman Filter, Book edited by: Vedran Kordic, ISBN 978-953-307-094-0, pp. 390, May 2010, INTECH, Croatia, downloaded from SCIYO.COM

The Mechatronics and Dynamic Modelling Laboratory of the Department of Industrial Engineering, University of Florence, as a partner of THESAURUS (Italian acronym for ‘TecnicHe per l’Esplorazione Sottomarina Archeologica mediante l’Utilizzo di Robot aUtonomi in Sciami’) project, has developed an innovative low-cost, multirole autonomous underwater vehicle, called Tifone. This article deals with the adopted methodologies for the autonomous underwater vehicle design: in particular, the main focus of this study is related to its propulsion system. According to the expected performances and requirements of THESAURUS project, the vehicle has to maintain good autonomy and efficiency (typical features of an autonomous underwater vehicle), with high manoeuvrability and hovering capabilities, which are more common of remotely operated vehicles. Moreover, cooperative underwater exploration and surveillance involve the use of a swarm of vehicles. In particular, the optimization of costs versus benefits is achieved through the design of a fleet of three multirole vehicles. Each autonomous underwater vehicle has five controlled degrees of freedom, thanks to four thrusters and two propellers: in this article, the preliminary design criteria concerning the vehicle and the design and testing of its actuation system are described.

With a view to the difficulty of the traditional hydrodynamic parameters experiments and theoretical calculation methods for autonomous underwater vehicle(AUV) and the drawback of optimum results tending to local optimization of the ever identification methods,a genetic algorithm based hydrodynamic parameters identification method of AUV is presented. This method has better robustness and can find the globally optimal point without initial values of parameters. It can provide a dynamic model for motion control,condition prediction and control system exploitation of AUV. Aimed at an open-frame AUV prototype named by CRanger-01,the genetic algorithm is used to identify the horizontal plane hydrodynamic parameters based on the analysis of the dynamic modeling. Then nineteen horizontal plane hydrodynamic parameters of CRanger-01 are identified,compared with the actual values,the identification errors are in the allowable range. By the simulation of the dynamic model,it demonstrates that the method can identify the hydrodynamic parameters of AUV effectively and can provide a reference for engineering practice.

The underwater environment severely constrains robotic navigation and communications, making the use of traditional multi-robot control and coordination schemes very difficult. These challenges are exacerbated on a new generation of low-cost autonomous underwater vehicles (AUVs) that lack a Doppler velocity log, acoustic modem, or high-end inertial sensors typically used for underwater robotic navigation and communications.This letter demonstrates multi-robot operations for low-cost AUVs via a novel and user-friendly operating paradigm that allows intuitive command and control of an AUV group. Each vehicle is equipped with a low-power and inexpensive acoustic system for navigation and receipt of operator commands. This system consists of a passive array of hydrophones and a timed acquisition and data processing stack that allows each AUV to self-localize relative to a time-synchronized acoustic beacon. Switching between different operational “modes” on the beacon causes it to broadcast different acoustic signals which, when received by the AUVs, result in the vehicles switching between different autonomous behaviors. These behaviors are defined in a beacon-centric coordinate system using pre-defined parameters unique to each vehicle; as a result, the movement of the beacon itself allows the operator to control the group-wide movement of all vehicles concurrently. This letter presents field experiments with three SandShark AUVs in which operational mode and beacon movement were controlled by an operator. However, by installing the beacon on an autonomous vehicle, this paradigm would provide a method for remote command and control of an arbitrarily large number of miniature, low-cost AUVs, without the need for sophisticated navigational sensors or acoustic modems.

This work proposes a design method for the propulsion system of autonomous underwater vehicles (AUVs) based on the to be accomplished tasks or trajectories. The method adapts to AUVs involving both fixed and vector thrusters. It is based on the inverse kinematic and dynamic models of the AUV performing a task of trajectory tracking. We first determine the actuation requirement in terms of propulsion effort according to the required task. These efforts are thus used to generate propulsion capabilities in the form of a “Thrust configuration matrix” (TCM). This matrix depends on the positions and orientations of the thrusters, but also thrust controlled angles of vector thrusters. In general, this matrix is compatible with any desired Cartesian trajectory and may include fixed or vector thrusters. From this matrix can be extracted the number, the type, position and orientation of thrusters constituting the obtained propulsion system. Thus, the robot's propulsion capabilities will match the characteristics of the to-be-followed trajectory.

To improve the observation capability of the ocean, the combination of the static cabled ocean observatory network and the dynamic autonomous underwater vehicle has attracted more and more attention. In this paper, a non-contact docking system for the autonomous underwater vehicle is developed to combine the advantages of the cabled ocean observatory network and the autonomous underwater vehicle. The system includes both acoustic and optical navigation, underwater wireless communication, non-contact power transfer, and monitoring and controlling of the docking system. This docking system was verified by sea trials at depths of 50 and 105 m. The autonomous underwater vehicle successfully docked 11 times, during which non-contact power transfer and wireless communication were completed. The charging power reached 682 W, with a total efficiency of 78.5%, and the efficiency of the power transfer unit was 92%. The rate of wireless data transfer reached 3.1 MB/s. For the first time, this docking system has realized complete homing and docking navigation, wireless communication and charging in a water depth of more than 100 m, thus establishing a good foundation for the combination of the cabled ocean observatory network and autonomous underwater vehicles.

The rapid development of Autonomous Underwater Vehicles (AUVs) has increased the demand for propulsion systems that balance thrust density, hydrodynamic efficiency, and acoustic discretion. This study presents a comprehensive numerical investigation of the performance of the Blue Robotics T500 thruster, embedded within the RAS-HA-X25 AUV’s internal conduit. Using transient Computational Fluid Dynamics (CFD) within the OpenFOAM framework, this research assesses the propulsive characteristics of the thruster across six distinct outlet geometries, including convergent jet nozzles and multi-lobed “daisy” configurations. To improve computational efficiency for parametric design, a calibrated actuator disc model was developed and validated against resolved-rotor simulations, revealing a 15% discrepancy attributed to tip leakage and hub vortex effects. Results show that at the operational advance ratio (J=0.167), the 60 mm convergent nozzle is the optimal configuration for maximising thrust, achieving a peak net thrust of 42 N. In contrast, the daisy-type lobed geometries, while causing a 50% reduction in absolute thrust compared to a standard cylindrical pipe, significantly homogenise the exit-plane velocity distribution and reduce swirl intensity. These findings indicate that lobed terminations provide a viable mechanism for reducing hydroacoustic signatures, offering a strategic “stealth” advantage for low-observable underwater platforms where acoustic discretion is prioritised over pure thrust density. This study establishes a robust methodology for optimising embedded propulsion modules in next-generation autonomous and hybrid underwater vehicles.

The shrimpfish, Aeoliscus strigatus, is an Indo-Pacific marine fish with a highly unusual posture - vertical with its head down - and remarkable maneuvering capabilities. It can translate straight up and down, turn in place and hover. These capabilities enable the shrimpfish to maneuver through complex tropical marine environments such as coral reefs and eel grass beds, and insert itself between the spines of sea urchins. Shrimpfish also use their maneuverability to track and capture tiny mobile crustaceans within the water column. An autonomous underwater vehicle (AUV) with such capabilities would have a number of interesting and potentially important applications in underwater inspection, sensing and sensor deployment. It will also serve to push the field of marine robotics into a challenging new area. We present the first results of a two-pronged biology and engineering research effort with the ultimate goal of developing an AUV with shrimpfish-like maneuverability. Biological measurements on real shrimpfish were performed to determine its hydrostatic stability. On the engineering side, a simple shrimpfish-inspired vehicle was developed as a testbed to study how fin motion can generate the different swimming behaviors seen in living Aeoliscus.

On Kanda port construction in Fukuoka prefecture, no fewer than 2,800 harmful chemical bombs have been discovered beneath the sea bottom so far. In advance of dredging in the port, we have carefully carried out magnetic inspection for looking for chemical bombs. Since a true target often gets mixed in a lot of suspicious metallic objects, we must cautiously draw up detected objects one by one. Use of a magnetic sensor only is uneconomical and inefficient. On account of these, we started a new three-year project of developing a sub-bottom synthetic aperture imaging sonar (sub-bottom SAS) system by using an autonomous underwater vehicle (AUV) and an autonomous surface vehicle for tracking the AUV. The AUV Tri-Dog 1, which was developed by T. Ura and H. Kondo, is going to be used. The AUV will be installed with a new sub-bottom SAS system and could perform stable and suitable navigation for SAS imaging in shallow water. The surface autonomous tracking vehicle can compensate for positioning error of the AUV and monitor sub-bottom imaging. The synthetic aperture sonar technology for sub-bottom imaging is now in the worldwide limelight, and several projects are ongoing. Since most of chemical bombs were buried up to 5 meters beneath the sea bottom, operating frequency 10 kHz to 30 kHz is expected to be useful for sub-bottom SAS. At the beginning of the project, we measured acoustical characteristics of sub-bottom sediments in Kanda port in 2010 May using a 33kHz single beam echo sounder RESON-Navisound 410 and a parametric sub-bottom profiler Innomar SES2000 Compact. Based on the acoustical characteristics, we will design a sonar projector and hydrophone arrays and a new surface autonomous tracking vehicle in this year.

Human vs robot: Comparing the viability and utility of autonomous underwater vehicles for the acoustic telemetry tracking of marine organisms

Understanding the mechanics of aquatic locomotion has been an active field of research for decades and continues to inspire technological solutions ranging from small-scale propulsion systems for autonomous underwater vehicles (AUVs) to larger-scale energy saving devices (ESDs) for ships. The bio-inspired thrust-producing kinematics are shared among most flapping-foil systems, however joint experimental and numerical research suggests that incorporating additional biomimetic features, such as hydrodynamic shape and elasticity, in new designs can enhance the efficiency. Focusing on the latter, the response of passively deforming wings is implicitly non-linear, since deformations affect the hydrodynamic load excitation and vice-versa. Therefore, fluid-structure interaction simulations are essential for accurate predictions of the wings’ response. In the present work, a cost-effective computational tool is proposed for the hydroelastic analysis of flexible flapping-foil thrusters, which consists of a 3-D unsteady boundary element method (BEM) weakly coupled with a finite element solver (FEM) based on plate elements. The verification of the present method is accomplished by means of comparison against experimental data from the literature. The prediction capabilities and the limitations of the weakly coupled BEM-FEM are discussed. Finally, the proposed numerical tools serve as the building blocks for the fully coupled BEM-FEM scheme that is currently under development.

In recent years, precious observations by autonomous underwater vehicle (AUV) have been performed. Tracking and navigation of AUV are important for precious observations. In Japan agency for Marine-earth Science and Technology (JAMSTEC) the observations with AUV ldquoURASHIMArdquo have been implemented in deep ocean area. AUV URASHIMA is navigated by an inertial navigation system (INS) mainly. The absolute position of AUV is tracked on the support vessel with super short base-line (SSBL) method of acoustic positioning. And sometime the own position in AUV is updated by the SSBL estimation result to correct the drift error of INS. However the SSBL is not so accurate. So the position correction includes the SSBL error and the position correction is performed drastically. In this paper, a method for accurate tracking of AUV and rapid correction of the INS status is proposed. The tracking is mainly achieved by SSBL on the support vessel. Additionally the INS data is transmitted from AUV including the acoustic positioning signal. The INS output of relative position to past own position is very accurate within short time. The INS data is used for tracking. Furthermore the position result estimated on the vessel is transmitted to AUV with next interrogation signal. And the own position in AUV is rapidly updated with accurate estimation. Some digital data including INS data is modulated with phase shift keying (PSK) method and direct sequence spread spectrum (DSSS) technique for transmission with acoustic positioning signal. The proposed method was considered by simulation. And good results were obtained.

As hypoxic water masses increase worldwide in duration and extent due to coastal eutrophication, advanced technology water quality monitoring by autonomous vehicles can increase our capability to document and respond to these environmental perturbations. We evaluated the use of a long endurance autonomous underwater vehicle (AUV) to map dissolved oxygen levels to determine the extent of hypoxia in a small bay (Greenwich Bay, USA.) known to experience summertime hypoxic episodes that have resulted in massive fish kills. During a 7.5 hr nighttime/early morning period in September 2004, the AUV collected dissolved oxygen, conductivity, temperature and depth data along three transects in the Greenwich Bay. The AUV utilized was a new solar powered vehicle designed for continuous survey operations. This vehicle, referred to as the SAUV II, was recently developed for the US Office of Naval Research for long endurance missions requiring monitoring, surveillance, and/or station keeping with real-time bi-directional communications to shore. The vehicle was pre-programmed to transit to designated waypoints at various depths. Following each transect, the vehicle surfaced, maintained a watch circle, and transmitted data to shore via an RF link. The survey provided the participating scientists with near real-time access to the physical characteristics of the water column with improved spatial and temporal resolution over traditional sampling for dissolved oxygen concentrations. This pilot study served as a test of the SAUV II to collect high resolution, near real-time water quality data in a nearshore, shallow embayment. Water column temperature and conductivity was relatively uniform over the survey path (temperature varied from 22-23 /spl deg/C; conductivity varied from 43030-43981 /spl mu/S). The depth of the vehicle varied from near-surface to a maximum of 9.5 m. Depth and dissolved oxygen concentrations were correlated. Dissolved oxygen concentrations ranged from approximately 2.4 to 6.0 mg/L over the course of the survey; mildly hypoxic conditions were encountered. The lowest concentrations of dissolved oxygen occurred at the deeper depths (>6 m). As the pilot study was performed in September, the late stage of a hypoxic event was most likely observed. Using the SAUV II to increase spatial sampling of dissolved oxygen in Greenwich Bay and conducting more frequent SAUV II surveys during the summer months will improve our understanding of hypoxia in this complex coastal estuary.

This paper presents an acoustic localization system for small and low-cost autonomous underwater vehicles (AUVs). Accurate and robust localization for low-cost AUVs would lower the barrier toward multi-AUV research in river and ocean environments. However, these AUVs introduce size, power, and cost constraints that prevent the use of conventional AUV sensors and acoustic positioning systems, adding great difficulty to the problem of underwater localization. Our system uses a single acoustic transmitter placed at a reference point and is acoustically passive on the AUV, reducing cost and power use, and enabling multi-AUV localization. The AUV has an ultra-short baseline (USBL) receiver array that uses one-way travel-time (OWTT) and phased-array beamforming to calculate range, azimuth, and inclination to the transmitter, providing an instantaneous estimate of the vehicle location. This estimate is fed to a particle filter and graph-based smoothing algorithm to generate a consistent AUV trajectory. We describe the complete processing pipeline of our system, and present results based on experiments using a low-cost AUV. To the authors' knowledge, this work constitutes the first practical demonstration of the feasibility of OWTT inverted USBL navigation for AUVs.

Consider the case where autonomous underwater vehicles (AUVs) are deployed to monitor a 3D underwater environment. This paper tackles the problem of guiding all AUVs to the destination while not colliding with a priori unknown 3D obstacles. Suppose that among all AUVs, only the leader AUV has an ability of locating itself, while accessing a destination location. A follower, an AUV that is not a leader, has no sensors for locating itself. Every follower can only measure the relative position of its neighbor AUVs utilizing its sonar sensors. Our paper addresses distributed controls, so that multiple followers track the leader while preserving communication connectivity. We design controls, so that all AUVs reach the destination safely, while maintaining connectivity in cluttered 3D environments. To the best of our knowledge, our article is novel in developing 3D underwater guidance controls, so that all AUVs equipped with sonar sensors are guided to reach a destination in a priori unknown cluttered environments. MATLAB simulations are used to validate the proposed guidance scheme in underwater environments with many obstacles.