Search

The proposed paper presents the design and development of the combined guidance & control strategies for the autonomous navigation of an unmanned vessel characterized by azimuth-based thrust architecture. Autonomous Marine Vehicles (AMVs) are consolidates technological tools commonly employed for different tasks such as exploration, sampling and intervention. With the final aim of autonomous shipping, the capabilities of AMVs have to be migrated and adapted towards the reliable and safe control of commercial-like unmanned vessel, that are taking place thanks to a number of technological research projects. The employment of new concept hulls and thrust configurations, as for instance Small Waterplane Area Twin Hull (SWATH) combined with Azimuthal propulsion (common propeller-based thruster with the capability of 360◦ rotation around the vertical axis), requires robust guidance techniques to provide precise and reliable motion control during navigation. The paper proposes a dual-loop guidance & control scheme able to provide advanced navigation capabilities. In particular, the inner control loop, devoted to the actuation of the azimuthal thrusters, allows the tracking of reference course angle (namely the autopilot). Such a control loop is characterized by a modified PID regulation scheme, where a novel adaptive derivative component is inserted in order to improve the convergence curve towards the required course reference. The outer guidance loop, based on Lyapunov/virtual-target approach, allows the vessel to track generic desired paths, thus enhancing the autonomous navigation capabilities also in constrained environments. The paper will provide a deep design & analysis approach for the developed techniques, as well as simulation results of the combined guidance & control scheme, proving the reliability of the proposed approach in different operative conditions. Experimental results will be provided, depending on the availability of the actual autonomous vessel (currently under final development/test phases and related to the specific project activities).&nbsp

This paper focuses on the control strategy needed by marine robots to be able to follow moving paths within a cooperative framework. This control aspect is essential in order to effectively perform emergency ship towing operations. In particular, these robots coordinate their motion, with the aim of performing an autonomous tying operation, linking the messenger line of a distressed ship to a salvage tugboat. Automatic guidance algorithms are developed in order to provide cooperation and coordination of robots' motion, in such a way to perform the knotting maneuver between the two employed vehicles. In particular, the major contribution of the present work in terms of adaptive control methodology consists in extending a well-known path following strategy for multi-vehicle cooperation to cope with moving reference paths. Extensive experimental testing validates the proposed concept, also pointing out the feasibility and effectiveness of the developed system in real-case scenarios. Copyright © 2016 John Wiley & Sons, Ltd.

This article proposes a swarm-based path-following guidance system for an autonomous marine multi-vehicle system. In particular, a team of unmanned surface vehicles is required to converge to and navigate along a desired reference path, while at the same time aggregating and maintaining a range-based formation configuration. First, a separate description is given for a swarm methodology, initially developed for small ground mobile robots and exploited to aggregate the robot team, and a virtual target–based path-following guidance system developed for unmanned surface vehicles, exploited to drive not the single vehicles but the robot formation as a whole. Then, the integration of the two proposed methodologies is reported and proven, in order to guarantee the feasibility and stability of the overall guidance framework. Simulative results are proposed to validate the effectiveness of the proposed methodology and to evaluate the system performances.

This paper focuses on the improvement of a swarm-based path-following guidance system for an autonomous marine multi-vehicle system. In the seminal idea a team of Unmanned Surface Vehicles (USVs) is required to join into a formation by means of a potential-based swarm aggregation methodology, while a virtual-target based guidance module drives the whole formation towards a desired reference path. Such a framework is then enhanced by taking into account the vehicles' positive surge speed constraint and maximum limit, typical of marine systems. The analysis of the results is reported to prove the feasibility and reliability of the proposed methodology, as well as the performance evaluation of the overall system.