Design of an autonomous surface vehicle (ASV)

Oil and gas companies are increasingly being forced to conduct their sub-sea pipeline inspections in increasingly more hostile and deeper waters. Typically, Remotely Operated Vehicles (ROV) are used for sub-sea pipeline inspections and these are controlled by experienced ROV operators from a surface support vessel, which tend to make ROV operations costly. Conversely, an Autonomous Underwater Vehicle (AUV) can perform sub-sea pipeline inspections without the need for a human operator. This paper sets-out to describe the development of a novel Hybrid AUV (HAUV) system, composed of two unmanned vehicles and designed specifically for sub-sea pipeline inspection. The first vehicle is a compact Unmanned Surface Vehicle (USV), which tracks a sub-sea pipeline from the sea surface. The second vehicle is a HAUV, which is connected to the USV via a fibre optic tether. Both vehicles operate together to automatically inspect sub-sea pipelines. The complete system is controlled by a remote control station on the surface. At this early stage of development, its capability is limited due to its size and battery power source but lab-scale units have been developed and have undergone field testing. Our team study is ongoing and endeavours to refine the HAUV system-capabilities enabling us to offer a cost-effective approach for sub-sea pipeline inspection in the near future.

A tethered flight vehicle such as Subzero III can be a reliable test-bed for AUV control techniques provided that the tether effects be removed by feed-forward control. To achieve the composite control idea, a numerical scheme for prediction of tether effects has been proposed and assessed. We argue that the composite control scheme can also be applied to the control of an ROV during the deployment of the umbilical. The H∞ approach has been applied to the design of the autopilots for autonomous underwater vehicles. The autopilots developed have the following features: (1) they have simpler structures than conventional H∞ design and the performance degrada tion caused by the controller order reduction is negligible; (2) rate feedback is applied for heading and depth control to improve tracking performance; (3) the overshoot specification is considered in the design by choosing suitable weighting functions. The results of both nonlinear simulations and water trials in two different tanks show that the autopilots are robust to model uncertainty, external disturbances and varying dynamics of the vehicle and exhibit good tracking performance. Thus the effectiveness of robust control for AUVs appears promising.

This thesis describes research work in the domain of underwater robotics. It is aimed towards improving performance and achieving partial or full autonomy in the rapidly increasing underwater resident robotics field, with the emphasis on the development of a suite of technologies for autonomous Remotely operated vehicle (ROV) docking. Fundamentally resident ROVs operating from shore demand high bandwidth, zero latency communication link which is often unavailable, thus high levels of automation are needed to compensate. This is especially important for time-critical tasks such as ROV docking. In addition, the docking station provides a download/upload link, charging point, and overall mechanical protection for the resident vehicles. Therefore, the docking of the ROV at the end of a mission is one of the crucial ROV tasks and often dictates weather window extents. Research in the literature mainly focuses on the docking to a static docking station, and although docking to a docking station deployed to the seabed is part of the thesis, the emphasis is on the docking to a Tether Management System (TMS) garage suspended from the floating platform/ship. This is used as a ROV docking scenario close to that of docking to a dock on a floating production platform such as floating oil production platform, floating wind platform or floating offshore fish farm seacage. Typically it is difficult to compensate for all motion between the ROV and the suspendedTMS/dock due to underpowered thrust,large inertia,and high drag forces, presenting a significant challenge. If the docking of a conventional work-class ROV to a suspended TMS proves successful, it presents a significant contribution and accelerates the path towards collaborative and integrated ROV and Autonomous surface vehicle (ASV) systems. This advancement will drive further improvements in the autonomous transition of the existing intervention subsea vehicles across large areas, primarily associated with the offshore wind sector. The work presented in the thesis consists of three major parts. The first is the visual pose estimation system developed to provide accurate relative position measurements between the ROV and the docking station/TMS. The developed system is based on active light beacons asymmetrically arranged to form a unique marker, and a machine vision camera. The system is built around conventional, industry-standard subsea LED lights and camera and it has been successfully tested both in a lake and in the ocean. The additional algorithm has been developed to reduce the pose estimation errors due to the low camera sensitivity to angle measurements from longer distances. The system has been developed for standard work-class ROV systems found throughout the sector, deployed from suspended cage type TMS. The second is autonomous docking of an industry-standard work-class ROV to cage type TMS using a visual-based pose estimation approach. This included both, autonomous docking to static TMS deployed to the seabed, and docking to TMS suspended from the ship. Evaluation of the system has been demonstrated through completion of offshore trials in the North Atlantic Ocean during January 2019. The third is a suspended TMS heave motion prediction method for ROV docking, based on the Adaptive Neuro-Fuzzy Inference System (ANFIS). With large ROV inertia and drag forces acting against it, the ROV is not agile enough to match a cage type TMS heaving motion. Therefore the ROV docking manoeuvre has to start before the ROV and the TMS align. This also includes matching the ROV to the docking depth that covers top or the bottom half of the TMS heave range, where TMS vertical speed is low. The method includes on-site neural network training based on previous TMS depth measurements and the TMS depth prediction. In addition, this method could be used standalone as a ROV pilot aiding tool.

The following addresses the control of an autonomous surface vehicle (ASV) to follow the trajectory made by an autonomous underwater vehicle (AUV) when the last is performing any given pre-programmed mission. In fact, it has been proved to be of great interest to have an ASV that could follow on the surface and even catch up the trajectory performed by the AUV, when executing a given mission. In order to achieve this desired coordinated motion between AUV and ASV, it would make sense just to program each of the vehicles with the same mission. However, due to the nature of vehicles, missions and also due to the localization system used, with this kind of solution some problems would arise, namely related with timings and synchronization, which are indeed difficult to overcome. The solution proposed here tries to estimate the AUV position, by tapping the signals exchanged between the former and each of the beacons of the acoustic localization network, and control and actuate the ASV in accordance.

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

Autonomous Underwater Vehicle (AUV) has played an increasingly important role in seafloor exploration, marine landscape observation and marine military field in recent years. Because the AUV’s endurance and communication capability are very limited, the AUV need to be regularly recycled for energy replenishment and data transmission. As a small unmanned surface platform, Unmanned Surface Vehicle (USV) whose technical development has been relatively mature can able to connect underwater unmanned platform with floating unmanned platform. Therefore, the study of the interrelationship between AUV and USV is full of prospects and challenges. In order to establish the connection between USV and AUV to further achieve the purpose of USV recycling AUV, this paper designs a new type of towing device with attitude measurement and attitude adjustment based on the existing towing technology and the Bernoulli equation. And the device is introduced from the aspects of mechanical design, force analysis and motion simulation. Through numerical simulation, it is found that the stabilizing wing can provide downward pressure for the towing device and the tail rudder can provide the diving moment for the towing device, which can ensure the depth stability of the towing device. The attitude of the towing device can be adjusted in real time by adjusting the angle of the tail rudder. In conclusion, this way takes an important step towards the wider practical application of AUV.

Cooperation among heterogeneous marine vehicles can offer several benefits to underwater applications, such as supporting the navigation of submerged robots by leveraging the information available to a surface vehicle. Within such context, this paper describes an acoustic positioning and communication protocol developed for the localisation of multiple Autonomous Underwater Vehicles (AUVs) by means of an Autonomous Surface Vehicle (ASV) equipped with an Ultra-Short BaseLine (USBL) device. To avoid packet collisions, access to the acoustic channel is managed through a time slot division mechanism. Unlike a classical Time Division Multiple Access (TDMA) protocol, the approach considered in this work consists of a centralised scheduling handled by the ASV, in which AUVs are localised at regular time epoch but can transmit only when queried. This allows to prioritise the number of position measurements taken by the ASV and then relayed back to the submerged vehicles, with the final goal of improving the navigation accuracy of the latter. The solution is also designed to handle the latency of acoustic communication and to correctly associate each position measurement with the corresponding acquisition time. Furthermore, it does not require any a priori synchronisation between the clocks of the vehicles involved and ensures complete decoupling between their navigation algorithms. Experimental activities in very-shallow waters, involving an ASV and two target nodes, were carried out to validate the multi-AUVs positioning system and to provide a characterisation of its performance.

Underwater communication cables transport large amounts of sensitive information between countries. This fact converts these cables into a critical infrastructure that must be protected. Monitoring the underwater cable environment is rare and any intervention is usually driven by cable faults. In the last few years, several reports raised issues about possible future malicious attacks on such cables. The main objective of this operational research and analysis (ORA) paper is to present an overview of different commercial and already available marine sensor technologies (acoustic, optic, magnetic and oceanographic) that could be used for autonomous monitoring of the underwater cable environment. These sensors could be mounted on different autonomous platforms, such as unmanned surface vehicles (USVs) or autonomous underwater vehicles (AUVs). This paper analyses a multi-threat sabotage scenario where surveying a transatlantic cable of 13,000 km, (reaching water depths up to 4000 m) is necessary. The potential underwater threats identified for such a scenario are: divers, anchors, fishing trawls, submarines, remotely operated vehicles (ROVs) and AUVs. The paper discusses the capabilities of the identified sensors to detect such identified threats for the scenario under study. It also presents ideas on the construction of periodic and permanent surveillance networks. Research study and results are focused on providing useful information to decision-makers in charge of designing surveillance capabilities to secure underwater communication cables.

In 2016, we developed a semi-submersible ASV (Autonomous Surface Vehicle) that can track and control AUVs (Autonomous Underwater Vehicle). However, in actual operation, the reliability of ASV's communication became a problem, so we modified the ASV and installed a new communication device called DCR (Digital Convenience Radio). DCR is Japanese communication standard using UHF band which deregulated maritime use in recent years. This device realized ASV's stable communication in the range of several kilometers.

Hydrodynamic investigations of a cross-domain vehicle with the capability of high-speed cruising on water surface

Gas hydrate production commenced from two production wells drilled in 1,000 m of water in the Nankai Trough, Japan, in May 2016. Two adjacent monitoring wells were drilled to monitor the in-situ event change of the hydrate reservoir over a two-year monitoring period. To achieve this monitoring purpose, an innovative design of wellbore gauges was installed downhole to provide valuable temperature and pressure data to show the dynamic nature of the gas hydrate dissociation front. Using two seabed located autonomous subsea monitoring systems, data were continually logged from the monitoring gauges since they were installed in May 2016. To gain access to the recorded wellbore data, early project thoughts revolved around either recovering the large subsea monitoring systems or deploying remotely operated vehicles (ROVs) to tieback umbilical cables from the two subsea monitoring systems to the drillship, once it arrived at the field site. These techniques proved to be expensive and of increased risk to both personnel and equipment. With a view to future safe and more cost-effective data harvesting techniques, a project was instigated to investigate using autonomous, unmanned surface vehicle (USV) along with vessel-based "dunker" methods to upload data from each of the monitoring wells using integrated high telemetry acoustic modem technology. The main objectives of the study were to verify data could be harvested and delivered to the client using a USV along with safe and repeatable piloting of the USV from a remote location. Two USV missions have since been conducted, one in June 2016 and the other in March 2017. Lessons learnt from the initial USV mission, such as higher than expected sea surface currents and thrust limitations of the USV, were incorporated into the second deployment. This resulted in roughly 200 days' worth of data being uploaded and delivered from each of the two monitoring wells. In this paper, we will outline how the project objectives were met and how some of the challenges, both technical and environmental, were overcome.

The use of autonomous marine robots has been rapidly increasing in the development of marine environments. This paper presents the development of an autonomous surface vehicle (ASV) and validation of autonomous navigation technologies. The ASV was developed as a testbed to validate fundamental navigation technologies for autonomous marine robots including both surface and underwater vehicles. The ASV was developed on a catamaran by integrating various sensors and power and electrical propulsion systems, navigation and control systems, and communication devices. As fundamental navigation technologies for ASV, waypoint tracking and obstacle avoidance are developed and tested. Further, using the ASV as a testbed to validate underwater navigation technologies, two types of underwater localization methods were developed. First, an acoustic-based navigation was developed by using acoustic sources as landmarks in underwater environment. The proposed acoustic-based navigation localized both vehicle and source by Kalman filter-based SLAM. Second, terrain-based localization as geophysics-based navigation was developed using a particle filter. Effective resampling can be achieved by using a measurement of terrain roughness. Both acoustic and terrain-based underwater navigation methods are implemented with the developed ASV, and the performance of the navigation methods are evaluated by comparing the estimated localization results to the ground truth acquired by GPS. Several field tests conducted in inland water environments demonstrate the performance of the developed vehicle and navigation algorithms.

Hybrid Tracking Controller for an ASV Providing Mission Support for an AUV

In this work a novel intelligent and distributed low-cost platform for marine observation is introduced. The observatory consists of an autonomous surface vehicle (ASV) and an autonomous underwater vehicle (AUV). This paper is focusing on potential search strategies for such an observatory. A novel search strategy based on Braitenberg search is introduced and the performance of this strategy is compared with the performance of inertia Levy-flight developed in recent work. Different settings of search algorithms are tested and their performance is evaluated using a computer simulation. It is shown that the combination of an ASV performing a pre-programmed search and an AUV performing inertia Levy-flight outperform a single AUV using inertia Levy flight for approximately 95 % of the chosen SGD positions. Both settings clearly outperform the introduced Braitenberg search.

Service providers for subsea inspection, maintenance, and repair (IMR) generally utilize remotely operated vehicles (ROVs) to evaluate and manipulate underwater infrastructure. The cost of these operations can be considerable, mostly due to the need to deploy a large surface vessel and crew to support the IMR campaign. Recent progress in marine autonomy, autonomous perception, and acoustic communication, however, unlocks new approaches to subsea IMR that could substantially reduce the overall cost of these activities and enable novel inspection objectives. This work describes perception and behaviors enabled by a novel multi-agent autonomous system comprising an autonomous underwater vehicle (AUV) and unmanned surface vessel (USV). We describe a unique AUV configuration that enables real-time processing of sensor data streams both on vehicle and at surface. Results on the metrological performance achieved in a field test campaign and the autonomous hydrocarbon leak behavior that these capabilities enable are presented.