Dula Nad

Using collaborative Autonomous Vehicles in Mine Countermeasures

This article describes concepts evaluated at NATO Undersea Research Centre (NURC) recent experiment as the part of Autonomous Mine Countermeasures (MCM) Program. We investigated the possibility of reacquisition of the target with the Autonomous Surface Vehicle (ASV), the possibility of controlling the position of the ASV relative to the target location, and tested the concept of guiding a neutralization weapon to the target based on the contact location obtained from the hunting mission performed by an Autonomous Underwater Vehicle (AUV). Second part of the article focuses on implementation in the open-source MOOS-IvP software framework. This framework allows for flexibility in control and mission planning. Guidance is covered by the MOOS-IvP implementation of the controller while the COTS autopilot handles low-level control. The control performance is verified in simulation and confirms arbitrarily small tracking error as well as tested in real, at-sea environment which included external disturbances, such as currents and waves. This experiment has shown that the collaborative use of autonomous systems has the potential to transform MCM capability, from a Cold War legacy focused on post-operations clearance with surface ships, to a quickly deployable system, autonomous system.

Tracking Divers: An Autonomous Marine Surface Vehicle to Increase Diver Safety

Diving is a high-risk activity due to the hazardous environment, dependence on technical equipment for life support, complexity of underwater navigation, and limited monitoring from the surface. This article describes a new concept of using an autonomous surface vehicle (ASV) as a private satellite that tracks divers, thus significantly increasing diving safety. Since the vehicle is above the diver at all times, acoustic communication with the diver interface in the form of an underwater tablet is more efficient and robust, which enhances diver navigation and enables reliable monitoring from the surface. This article focuses on a diver-tracking control structure that uses a diver motion estimator to determine diver position, even in cases when acoustic position measurements are not available.

Sigma-point Unscented Kalman Filter used for AUV navigation

This paper presents an implementation of the Sigma-point Unscented Kalman Filter (SP-UKF) used in the simulated task of open-water navigation of two types of AUV. The first simulated vehicle is a large cruise-type vehicle modeled after the Instituto Superior Tecnico, Lisbon vehicle Infante. The second is a small, almost fully actuated vehicle with tunnel thrusters modeled after the SSC Pacific, San Diego vehicle CETUS II. The SP-UKF shows itself, after properly taking care of implementation details, to be a robust methodology which allows for efficient and correct navigation, aided by several typical sensors (DVL, USBL hydroacoustic localization systems, AHRS). The influence of currents on the navigation, and the ability of estimating the current components is also researched. The navigation fix is fed back to the low-level control loops aboard each vehicles to achieve sane and rational navigation of the waterspace that follows stably and robustly the command signals.

Coordinated Navigation of Surface and Underwater Marine Robotic Vehicles for Ocean Sampling and Environmental Monitoring

Water pollution generated by accidental spill of hazardous materials is a growing problem worldwide. There is an urgent need for a tool that would help environmental response teams perform rapid understanding of the location and the extent of the spill to effectively establish an appropriate response. This paper presents a cooperative robotic system for environmental monitoring consisting of an autonomous underwater vehicle (AUV) and an autonomous unmanned surface vehicle (USV). The main contributions of the paper are a systematic description of the design and implementation of the proposed cooperative robotic system, a novel human-on-the-loop (HOTL) approach applied on the system for environmental monitoring, and demonstration of the results of the open-sea experiments on pollution deliberately caused by harmless Rhodamine water tracing (WT), carried out in Cartagena, Spain, in June 2015. The proposed HOTL system provides near real-time pollution measurement data, while not consuming a significant amount of human time and effort. It supports decision-making and allows the operator to initiate the most adequate mission in a current situation, i.e., ensures mission change on-the-fly. While the AUV samples the ocean, the USV maintains the localization and communication data transfer to the control center and corrects the AUVs dead reckoning error.

Sonar aided navigation and control of small UUVs

This paper addresses the problem of guiding a simple unmanned underwater vehicle (UUV) from a more capable, sonar equipped, platform, preferably an autonomous underwater or surface vessel (AxV). One application of this concept, considered in this article, is autonomous mine neutralization and disposal. First, a sonar equipped AxV acquires a possible target in the sonar image. Once the target location is known, an expendable UUV is released. The UUV position is determined from sonar imagery onboard the AxV. This minimal information is sent to the UUV via acoustic link so that it can converge towards the desired target. With this approach, complex and expensive sensors are removed from the expendable vehicle, which now becomes a simple actuation system that carries the neutralization payload, and this in turn greatly increases cost efficiency. Although we review the concept in the domain of mine countermeasures (MCM) it is applicable to other problems where navigation aiding between platforms is beneficial. This paper focuses on preliminary results obtained in numerous pool and field experiments during different phases of system development.

Auditory Interface for Teleoperation - Path Following Experimental Results

Abstract For teloperated unmanned vehicles, mishaps tend to occur during the periods of high workload, in situations where the operator must perform complex and stressful tasks. However, with many tasks performed simultaneously with flying, the relevant information is typically dispersed on a number of screens overloading the operators visual channel. In order to address these unique human-factors problems associated with unmanned vehicles we suggest the use of an auditory display as a mean to reduce visual workload, to enhance situation awareness, and mitigate the visual and cognitive demands of contemporary marine teleoperations. Experiments were performed on the remotely operated surface marine platform (PlaDyPos) developed at the Laboratory for Underwater Systems and Technologies, Faculty of Electrical Engineering and Computing, University of Zagreb. The results show that the concept, guidance-by-sound is feasible in the real environment. The results are in line with previously obtained results from the real-time simulator showing that tracking quality can be further improved introducing supernormal auditory cues in order to provide better-than-normal operators auditory resolution in the frontal region. We conclude that the use of hearing in the form of the auditory display emerges as an important advantage. Since practice has a major effect on performance, there is definitely more room for improvement in using interfaces we are not trained for.

DiverNet — A network of inertial sensors for real time diver visualization

This paper describes the DiverNet system that allows real time reconstruction of divers posture and its visualization using a virtual 3D model. DiverNet is a network consisting of 17 inertial sensors mounted on divers body, enabling calculation of orientation of each body part. Based on the obtained data, diver posture can be visualized. In addition to that, DiverNet allows integration of additional sensors for measuring physiological parameters such as breathing rate. This is the first time such technology is used in the underwater. Obtained data will be used to increase diver safety by monitoring the diver in real time, as well as developing tools for understanding diver behaviour and automatically recognizing possible signs of trouble. The paper focuses on technical description of the developed system, as well as the software used for data analysis and visualization.

Texture segmentation applied to P. Oceanica Beds' upper boundary tracking by ROVs

Abstract The paper deals with an image processing technique for texture segmentation. By way of texture segmentation, a binary image is constructed and used to fit a line of the dominant direction of propagation of the texture in the image plane. The texture is captured by an oblique angle that positions the image plane in a near vertical orientation to the sea bottom plane. The texture being recognized in the experiment is that of Posidonion Oceanicœ , the benthic community (meadow or bed) of the Neptune grass Mediterranean endemic. It is the motivation of this paper for the dominant direction of propagation of the texture segment in the image plane to be used as a measure of the true direction of propagation of the upper border of Posidonion Oceanicœ in a feedback control loop that will enable the vehicle to autonomize the task of upper border tracking. The algorithm for extraction features four distinct phases: multi-resolution analysis using wavelets, vector quantization, post-processing of the obtained binary image and the extraction of the line parameters. The classification and line-fitting procedure are computationally optimized and made more robust by using weights in the Least Squares fitting procedure, and using nonlinear binary-image domain processing.

A modular approach to system integration in underwater robotics

Underwater exploration is experiencing an ever increasing usage of both autonomous and remotely operated robotic vehicles. Vehicles are typically equipped with several sensors depending on the mission type being carried out. Integration of all these systems together, as well as obtaining data from them presents a significant challenge. This article describes a software architecture which represents all entities in the system as equivalent modules, while hiding their specifics from the user. Each module in the system is fully defined only by the data it produces and the commands it accepts. Modules are coupled together using a communication interface which again hides the underlying protocol from the user, and is based solely on message exchange. This architecture allows quick reconfiguration of the vehicle, easy integration of various sensor systems and provides the application developers with a higher level of abstraction.

AUV based mobile fluorometers: System for underwater oil-spill detection and quantification

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.