Unmanned Semi-submersible Vehicle Research Articles

Development and Testing of Unmanned Semi-Submersible Vehicle

A semi-submersible vehicle has most of its body submerged in the water, while keeping a small platform above the water surface for communication and access to atmospheric air. This vehicle has low visibility, good seaworthiness and low-wave drag in certain speed regimes, and thus, it is potentially suited for special military and civil applications. The main objective of this study is to report on construction and testing of a small, low-cost vehicle of this type, as well as initial tests in open water to characterize its power requirements and trim values at different speeds and settings and to demonstrate some functional capabilities. The vehicle was operated under remote manual control and instrumented with a variety of sensors gathering internal and environmental information. The presented description of the designed system, construction, sensors, data acquisition and control and communication systems, as well as test results, can benefit engineers interested in developing semi-submersible vehicles.

New Cost-Effective Technologies Applied to the Study of the Glacier Melting Influence on Physical and Biological Processes in Kongsfjorden Area (Svalbard)

The Arctic region is greatly affected by climate change, with evident alterations in both physical and biological processes: temperatures are changing at a rate that is twice the global average and phytoplankton productivity is directly affected by ice melting. Continuous monitoring of this ecosystem is fundamental to gain greater understanding of the impact of changes on the natural environment, but the Global Ocean Observing System only provides partial coverage in these extreme areas, which are particularly difficult to reach. Technological progress in oceanographic measurement capabilities is indispensable for the implementation of marine observatories, especially in these remote regions. In recent years, autonomous systems and cost-effective technologies have proved to be valuable for increasing spatial and temporal coverage of data. This is the case with the innovative ArLoC (Arctic Low-Cost) probe, which was designed and developed for easy integration into various types of platforms, enabling continuous measurement of temperature, pressure and fluorescence of chlorophyll a. This work reports on the results of two scientific campaigns carried out in Kongsfjorden (Svalbard Islands) in 2018 in the framework of the UVASS (Unmanned Vehicles for Autonomous Sensing and Sampling) research project. The ArLoC probe was integrated onboard the PROTEUS (Portable RObotic TEchnology for Unmanned Surveys) unmanned semi-submersible vehicle and this allowed us to collect important data in the stretches of sea near tidewater glacier fronts. The acquired data showed several significant effects of glacier melting such as: high temperature and salinity gradients, which cause considerable variations in water mass stratification, and an increase in turbidity and the chlorophyll a concentration, which directly affects primary productivity and the trophic chain. During the surveys, ArLoC proved to be an easy-to-integrate, very reliable instrument, which permitted high spatial resolution investigation of ecological processes during glacier melting as never studied before.

Monitoring of Sea-Ice-Atmosphere Interface in the Proximity of Arctic Tidewater Glaciers: The Contribution of Marine Robotics

The Svalbard archipelago, with its partially closed waters influenced by both oceanic conditions and large tidal glaciers, represents a prime target for understanding the effects of ongoing climate change on glaciers, oceans, and ecosystems. An understanding of the role played by tidewater glaciers in marine primary production is still affected by a lack of data from close proximity to glacier fronts, to which, for safety reasons, manned surface vessels cannot get too close. In this context, autonomous marine vehicles can play a key role in collecting high quality data in dangerous interface areas. In particular, the contribution given by light, portable, and modular marine robots is discussed in this paper. The state-of-the-art of technology and of operating procedures is established on the basis of the experience gained in campaigns carried out by Italian National Research Council (CNR) robotic researchers in Ny-Ålesund, Svalbard Islands, in 2015, 2017, and 2018 respectively. The aim was to demonstrate the capability of an Unmanned Semi-Submersible Vehicle (USSV): (i) To collect water samples in contact with the front of a tidewater glacier; (ii) to work in cooperation with Unmanned Aerial Vehicles (UAV) for sea surface and air column characterisation in the proximity of the fronts of the glaciers; and (iii) to perform, when equipped with suitable tools and instruments, repetitive sampling of water surface as well as profiling the parameters of the water and air column close to the fronts of the tidewater glaciers. The article also reports the issues encountered in navigating in the middle of bergy bits and growlers as well as the problems faced in using some sensors at high latitudes.

First Rocketsonde Launched from an Unmanned Semi-submersible Vehicle

The unmanned semi-submersible vehicle (USSV) developed by the unmanned surface vehicle team of the Institute of Atmospheric Physics is an unmanned, rugged, and high-endurance autonomous navigation vessel designed for the collection of long-term, continuous and real-time marine meteorological measurements, including atmospheric sounding in the lower troposphere. A series of river and sea trials were conducted from May 2016 to November 2017, and the first rocketsonde was launched from the USSV. Real-time meteorological parameters in the marine atmospheric boundary layer (MABL) were obtained, including sea surface temperature, and vertical profiles of the pressure, temperature, relative humidity, wind speed, and wind direction. These data are extremely useful and important for research on air-sea interactions, sea surface heat and latent heat flux estimations, MABL modeling, and marine satellite product validation.

Experimentally Verified Depth Control of an Unmanned Semi-Submersible Vehicle

This paper considers the control of one unmanned semi-submersible vehicle (USV), named BQ-01, where the submersible depth cannot exceed a few meters in the presence of environmental disturbances. Consequently, the depth control performance measures and the rejection of disturbances, such as those due to sea waves, must be within pre-determined ranges to ensure maximum use of such vehicles. This paper develops a control scheme that combines the state feedback control and rule-based supervision for depth control, where the entries in the feedback control matrix are adjusted by rules formulated from the state errors in the USV diving plane. Surge speed also plays an important role in adjusting control parameters because of its coupled relationship with the state depth of the diving plane. The results from sea trials are given and confirm the potential of the design.

Software-In-the-Loop based Modeling and Simulation of Unmanned Semi-submersible Vehicle for Performance Verification of Autonomous Navigation

Since an unmanned semi-submersible is mainly used for the purpose of carrying out dangerous missions in the sea, it is possible to work in a region where it is difficult to access due to safety reasons. In this study, an USV hull design was determined using Myring hull profile, and reinforcement work was performed by designing and implementing inner stiffener member for 3D printing. In order to simulate a sea state 5.0 or more at sea, which is difficult to implement in practice, a regular and irregular wave equation was implemented in Matlab / Simulink. We performed modeling and simulation of semi - submersible simulation based on DMWorks considering the rolling motion in wave. To verify and improve unpredicted errors, we implemented a numeric and physical simulation model of the USV based on software-in-the-loop (SIL) method. This simulation allows shipbuilders to participate in new value-added markets such as engineering, procurement, construction, installation, commissioning, operation, and maintenance for the USV.

Maneuverability Modeling and Visual Simulation for Unmanned Semi-Submersible Vehicle

The ship maneuverability model and visual simulation methods of Unmanned Semi-submersible Vehicle (USV) were discussed. Firstly, the five-DOF mathematical model for USV was established. Secondly, the visual marine environment was also established by the way of using VEGA software and CREATOR model software. Thirdly, the system architecture for the USV visual simulation was designed under the framework of MFC. Finally, the maneuver simulation tests on the sea surface and under the sea were done for the USV. The maneuvering simulation results were vivid, and it showed that the mathematic model has capable of response the maneuverability of the USV on the sea surface and under the sea. The method presented here has some practical usage. And the simulation system can be a visual debugging platform for those who designing the USV control system.

ILOS Guidance - Experiments and Tuning

A recently proposed Integral Line-of-Sight (ILOS) guidance law is applied to an underactuated Unmanned Semi-Submersible Vehicle (USSV) for path following of straight lines. Derived from the popular Line-of-Sight guidance, the ILOS methods adds integral action to increase robustness with respect to environmental disturbances such as sea currents, wind and waves that unavoidably affect maritime operations. Integral action makes the vehicle sideslip and hence compensate for the disturbances acting in the underactuated sway direction. Furthermore, the integrator of the ILOS implemented in this paper has embodied, analytically derived, anti-windup properties. It is shown that even if an accurate model of the vessel dynamics is not available, a simple kinematic model and a few test runs give enough information to correctly choose the guidance law parameters. Data from sea trials are presented to verify the ILOS theory and give an experimentally based understanding of the behavior of the USSV when different look-ahead distances and integral gains are used.