Underwater interferometric radar sensor for distance and vibration measurement

Modeling of the Ballard-Mark-V proton exchange membrane fuel cell with power converters for applications in autonomous underwater vehicles

The author describes autonomous underwater vehicle (AUV) developments and applications world-wide, AUV development in China, and AUV trends. Besides developments in China, those in the USA, Canada, the United Kingdom, France, Germany, Japan, and Russia are discussed, such as deep ocean modelling, ocean bottom exploration, ocean bottom sampling, deep ocean work platform, underwater survey, and so on. A testbed facility is described. AUV research topics are outlined. >

Localization and tracking are basic services for the applications of autonomous underwater vehicles (AUVs). Although they are closely related, the localization or tracking is usually studied independently. This paper addresses a joint localization and tracking issue for an AUV, subject to asynchronous clocks in physical channel and state disturbances in control channel. We first develop an asynchronous localization algorithm to estimate the position of an AUV, wherein the clocks on AUV and buoys are not required to be synchronized. With the estimated position, a model-free tracking controller is designed for an AUV to track the reference trajectory. Particularly, the time-delay estimation and dynamic gain strategies are adopted to reduce the influence of state disturbances. Moreover, the convergence conditions and Cramer–Rao lower bounds for the localization algorithm are derived. For the tracking controller, Lyapunov functions are constructed to analyze the stability, through which the sufficient conditions for asymptotic stability are presented. Finally, simulation and experiment results are given to show the effectiveness of the proposed method. It is demonstrated that the asynchronous localization algorithm in this paper can effectively eliminate the impact of the clock skew and offset. Meanwhile, the tracking accuracy can be significantly improved.

Homing and docking capabilities are essential in many autonomous underwater vehicle (AUV) applications. The paper tackles the homing problem, leaving aside the actual docking of the vehicle. Homing is often performed by means of acoustic sensors providing the bearing of the beacon to be reached in the vehicle frame. This measurement, combined with the vehicle's heading, is used directly to steer the AUV towards the goal. The algorithm described in the paper only uses acoustic range measurements to the beacon. The difficulties of this approach are due to the fact that a single range measurement does not completely constrain the beacon's position in the vehicle frame nor does it define the direction to follow. In addition, range measurements are noisy and sometimes spurious, and underwater currents affect dead-reckoning measurements. The AUV has then to maneuver, filter the range measurements and estimate the underwater current in order to maintain an estimation of the beacon's position. The homing procedure consists of obtaining an initial estimate of the beacon's position and of the underwater current components by appropriate maneuvers. The initial estimates are further refined during the actual displacement towards the beacon by means of a Kalman filter.

As a kind of small size mobile platform, autonomous underwater vehicles (AUV) are playing more and more important role in different marine fields such as underwater monitoring and construction. While acoustic communication offer an effective communication link for AUV, under the confined spaces in which small AUVs usually work, the structured obstacles and closure or semi-closure barriers pose serious challenges to communication link due to acoustic sheltering and significant reverberation. The underwater acoustic network is capable of improving acoustic connectivity of AUV via the distributed communication link of different nodes. In this paper, an acoustic network is designed and evaluated for communication support of AUV in a small lake with dense piers. While the presence of piers lead to obvious performance degradation of point-to-point acoustic communication, the experimental results verified the effectiveness of acoustic network for improving connectivity of AUV in confined space.

The accumulation of navigation errors (drift) is a problem in many applications of autonomous underwater vehicles (AUVs), particularly during long-duration underwater surveys. Traditional methods for correcting drift require either surfacing of the vehicle for a global navigation satellite systemupdate or use of an independent acoustic positioning system. These methods may not be desirable or possible due to mission constraints. We propose a solution to this problem completely underwater and without the aid of external navigation systems. The approach is based on an operational concept that uses a modified paired-track survey pattern combined with through-the-sensor navigation corrections from a seafloor imaging sonar. We describe the operational concept, derive a model for its performance limits, validate this model, and demonstrate the concept with real experiments at sea. Using this approach, we provide an opportunity to use either coherent or incoherent through-the-sensor positioning corrections for a mission length increase of only the product of the intratrack spacing and the number of track pairs. We show results from a proof-of-principle experiment using data collected by the ${\text{300-kHz}}$ synthetic aperture sonar of the NATO Centre for Maritime Research and Experimentation's Minehunting Unmanned underwater vehicle for Shallow water Covert Littoral Expeditions.

An ultrasonic transducer array for velocity measurement in underwater vehicles

To promote underwater construction, the tools such as underwater robotic manipulator system, underwater vehicles and so on are necessary. Furthermore, these system need an accurate 3D position parameters. If no position information for automatic control system that system is difficult to be operated. Hence, it is important to take position information. Although 3D position camera can offer 3D position parameters, it has still some deviation. In addition, the manipulator system need accurate distance information for fast and accurate operation. Hence, an accurate distance measurement system is necessary for a remotely teleoperated robotic manipulator system for underwater constructions. This paper focus on the distance measurement study to offer a accurate target distance information. The information can combine with 3D position camera to obtain more accurate 3D position parameters to offer a useful position information for underwater constructions, with a remotely teleoperated robotic manipulator system. In this paper, three distance measurement system, includes commercial ultrasonic distance measurement system, fabricated ultrasonic system and a laser distance measurement system is study. The commercial distance measurement system have a distance measurement system rang 8~35 cm, plusmn0.1 cm. However, a short distance measurement is difficult to be measured with the measurement system. On the other side, the fabricated measurement system can measure a short distance. Information from 0~5 cm, accuracy plusmn0.3 cm. The fabricated distance measurement system fabricated with PZT thin film. In this study, a horn is added to improve the accuracy of distance measurement. In addition, the laser distance measurement system, measurement system is used to measure the distance information also in this study. The combination of these distance measurement system to form a multiple range distance measurement can offer a long measurement range for accurate distance measurement underwater. A detailed experiment is to be studied in the future. Furthermore, the distance measurement system has been offered a distance measurement in a remotely teleoperated robotic manipulator system for underwater constructions

The use of robotic systems in marine and freshwater research has expanded rapidly over the past two decades. Uncrewed Surface Vehicles (USVs), autonomous underwater vehicles, and remotely operated vehicles are now routinely employed to collect physical, chemical, and biological data across a wide range of environments. These technologies offer several well-established advantages, including improved access to remote or hazardous areas, enhanced safety for personnel, and increased spatial and temporal resolution of measurements. In parallel, advances in sensor technology, miniaturization, and power efficiency have enabled the integration of increasingly sophisticated instrumentation on uncrewed platforms. Despite these developments, the practical adoption of robotic technologies by the broader research community remains uneven. Many systems are costly, technically complex, and require substantial engineering expertise to deploy and maintain. Field operations are often constrained by logistical challenges, particularly the availability and expense of research vessels. Furthermore, the specialized nature of robotic systems frequently necessitates close collaboration between engineers and domain scientists, which can limit flexibility and increase operational overhead. These factors collectively create a high threshold for use, particularly for small research groups, early-career scientists, and projects with limited budgets. There is, therefore, a clear need for robust, user-oriented robotic platforms that function as general-purpose workhorses for aquatic research. Such systems should be deployable with minimal training, reduce logistical dependencies, and operate either in conjunction with or independently of traditional research infrastructure. USV Pamela was developed in response to this need, with an explicit focus on simplicity, modularity, and accessibility.

The capability of an Autonomous Underwater Vehicle (AUV) or Remote Operated Vehicles (ROVs) to communicate with underwater sensor nodes or a docking station, for the exchange or transfer of data gathered during a survey mission, requires an high-speed short-range communication link. This is important because of the global attention to the underwater communication applications. To this end, underwater antennas will play a significant role in ensuring good data rates and propagation distances for these applications. In this paper, the performance of three antennas, specifically, loop, dipole and J-pole is assessed through simulation for usage in fresh and sea water operating in the High Frequency (HF) band. The antennas were designed in FEKO, an electromagnetic simulation software and their performance is assessed in terms of bandwidth and directivity. The results obtained shows that the J-pole antenna has significant advantages in term of the measured parameters over the other antennas. Experimental results of the reflection coefficient of the J-pole antenna in fresh water are given that agree well with the simulation results.

The tragic Deepwater Horizon accident in the Gulf of Mexico in 2010 as well as increase in deepwater offshore activity have increased public interest in counter-measures available for sub-surface releases of hydrocarbons. Available remote-sensing techniques are efficient and well developed for surface disasters but they are not useful underwater. Along these lines, this paper analyzes application of Autonomous Underwater Vehicles (AUV) with integrated submersible fluorometer for underwater detection of hydrocarbons. Experiments with rhodamine, which was used as a replacement for oil, showed that the proposed system can be efficiently used both as an input into numerical model and consequent visualization of spatial distribution of pollutant.

Seabed inspection is one of the most sought-after applications for autonomous underwater vehicles (AUVs). Acoustical sensors, such as side-scan sonars and forward-looking sonars (FLSs), are commonly favored over optical cameras to carry out such a task. Indeed, sonars are not influenced by illumination conditions and can provide high-range data. However, due to the lack of features and low resolution, acoustical images are often hard to interpret with conventional automatic techniques, forcing human operators to analyze thousands of collected images to identify the so-called objects of potential interest (OPIs). In this article, we report the development of an automatic target recognition (ATR) methodology to identify and localize OPIs in FLS imagery. Such detections have been then exploited to realize a virtual world model with the probabilistic multiple hypothesis anchoring data association and model tracking algorithm. Distinct models of convolutional neural networks have been trained with a data set acquired in May 2019 at the Naval Support and Experimentation Centre (Centro di Supporto e Sperimentazione Navale—CSSN) basin in La Spezia, Italy. The ATR strategy has been successfully validated offline with the data gathered in October 2019 in the same site where the seabed targets were replaced and relocated. As regards the world modeling technique, it has been preliminarily tested on a simulated scenario built upon unmanned underwater vehicle Simulator. Finally, both the ATR and world modeling systems were on-field tested in October 2020 at the CSSN basin in a multivehicle architecture by employing an acoustical channel between FeelHippo AUV and an autonomous moving buoy.

Potential applications of autonomous underwater vehicles

The issues on the application of autonomous underwater vehicles for assessing the abundance, biomass, distribution and reserves of invertebrates in the marine benthic ecosystems and on the environmental monitoring are discussed. An example of the application of methodology to assess some of the quantitative characteristics of macrobenthos is provided based upon using the information obtained from the TSL AUV in the Peter the Great Gulf (the Sea of Japan) in the Bay of Paris and the Eastern Bosphorus Strait within the area of the bridge leading to the Russian island. For the quantitative determination of the benthic invertebrate reserves, the values of biomass density of specific species are determined. Based on the data of direct measurements and weightings, the equations of weight dependencies on the size of animals are estimated according to the studied species that are well described by the power law dependence.

The article discusses issues of ensuring effective and reliable measurement and control of drill string vibration. A system for active measurement and control of drill string vibration is presented. The system combines both wellhead equipment elements and downhole equipment. At that, there is a specially designed hydromechanical extensional vibration sensor used in wells. The wellhead equipment includes elements of record and analysis of obtained data about drill string vibration. Moreover, the system includes wellhead equipment for stopping vibration. The article analyses optimal parameters for the shape of the hydromechanical vibration sensor. Its optimal shape is established.