Aspects of a Reliable Autonomous Navigation and Guidance System for an Unmanned Surface Vehicle

This paper describes a novel navigation and guidance (NG) system designed to address the issue of receiving unreliable navigational data considering an unmanned surface vehicles (USVs). In the NG system, a confidence rate determination method has been designed to identify the uncertainty of the acquired data. According to the confidence rate, the risks from inaccurate data can be properly analysed facilitating the system generating a more reliable guidance route. The route is calculated using a newly developed algorithm named the constrained FM*. The new NG system has been verified in simulation environments with results proving the effectiveness and capabilities of the system

Development of voyage optimization algorithms for sustainable shipping and their impact to ship design

The environmental impacts from shipping and the societal challenges of human and property losses caused by ship accidents are pressuring the shipping industry to improve its energy efficiency and enhance ship safety. Voyage optimization is such an effective measure that has been widely adopted in today’s shipping market. The voyage optimization algorithm is the dominant part of any voyage optimization methods. The main objective of this thesis is to develop sophisticated voyage optimization algorithms, explore their applications to sustainable ship operations, and study its impact on ship fatigue design.In this thesis, five commonly used voyage optimization algorithms are first implemented and compared to provide a foundation for understanding optimization algorithms. A three-dimensional Dijkstra’s algorithm is then developed with further improvement based on the comparison. It can provide globally optimal solutions and conducting multi-objective voyage optimization. An engine-power based multi-objective optimization algorithm is proposed for the aid of ship operations with power-setting in their navigation system. Furthermore, the influence of the uncertainties from voyage optimization inputs, e.g., metocean forecast, implemented ship performance models and voyage optimization algorithms, on the optimization results is investigated. Moreover, the capabilities of the proposed voyage optimization algorithms to handle other optimization objectives, i.e., less fatigue damage accumulation and lower fatigue crack propagation rate, is also investigated. Meanwhile, two statistical wave models are compared to study the variation of a ship’s encountered wave environment for ship fatigue design. The impact of voyage optimization aided operations on a ship’s encountered wave environments and fatigue life assessment is also researched in this thesis. The three-dimensional Dijkstra’s algorithm addresses the limitations of conventional voyage optimization algorithms and allows for voluntary speed variation. It has a great potential of saving fuel up to about 12% in comparison with the case study ship’s actual sailing routes. The ship engine setting-based optimization algorithm provides a scheme based on a genetic algorithm and dynamic programming concept. It has the potential to save fuel up to approximately 14.5% compared to the actual sailing routes. This study also shows that metocean uncertainties in the voyage optimization process have great influence on the optimization results, i.e., 3-10% difference in fuel consumption for the same voyage optimization method. In addition, statistical wave models have been proven to capture ship-encountered wave statistics. It is also shown that the actual wave environments encountered by ships differ significantly from the wave scatter diagram provided by class guidelines. A good voyage optimization method can help to extend a ship’s fatigue life by at least 50%.Keywords: Dijkstra’s algorithm; Energy efficiency; Expected time of arrival (ETA); Genetic algorithm; Metocean forecast; Ship safety; Sustainable shipping; Voyage optimization algorithms

A novel path planning approach for smart cargo ships based on anisotropic fast marching

Path planning is an essential tool for smart cargo ships that navigate in coastal waters, inland waters or other crowded waters. These ships require expert and intelligent systems to plan safe paths in order to avoid collision with both static and dynamic obstacles. This research proposes a novel path planning approach based on the anisotropic fast marching (FM) method to specifically assist with safe operations in complex marine navigation environments. A repulsive force field is specially produced to describe the safe area distribution surrounding obstacles based on the knowledge of human. In addition, a joint potential field is created to evaluate the travel cost and a gradient descent method is used to search for appropriate paths from the start point to the end point. Meanwhile, the approach can be used to constantly optimize the paths with the help of the expert knowledge in collision avoidance. Particularly, the approach is validated and evaluated through simulations. The obtained results show that it is capable of providing a reasonable and smooth path in a crowded waters. Moreover, the ability of this approach exhibits a significant contribution to the development of expert and intelligent systems in autonomous collision avoidance

Extracting Maritime Traffic Networks from AIS Data Using Evolutionary Algorithm

The presented method reconstructs a network (a graph) from AIS data, which reflects vessel traffic and can be used for route planning. The approach consists of three main steps: maneuvering points detection, waypoints discovery, and edge construction. The maneuvering points detection uses the CUSUM method and reduces the amount of data for further processing. The genetic algorithm with spatial partitioning is used for waypoints discovery. Finally, edges connecting these waypoints form the final maritime traffic network. The approach aims at advancing the practice of maritime voyage planning, which is typically done manually by a ship’s navigation officer. The authors demonstrate the results of the implementation using Apache Spark, a popular distributed and parallel computing framework. The method is evaluated by comparing the results with an on-line voyage planning application. The evaluation shows that the approach has the capacity to generate a graph which resembles the real-world maritime traffic network

The angle guidance path planning algorithms for unmanned surface vehicle formations by using the fast marching method

By deploying multiple USVs as a formation fleet, benefits such as wide mission area, improved system autonomy and increased fault-tolerant resilience can be achieved. To efficiently and effectively navigate the USV formation, path planning algorithms are required to generate optimal trajectories and provide practical collision avoidance manoeuvres. In particular, as the USV is underactuated and is restricted by various motion constraints, this paper has presented a new algorithm named the ‘angle-guidance fast marching square’ (AFMS), to make the generated path compliant with vehicle's dynamics and orientation restrictions. Based upon the AFMS, a formation path planning algorithm has been proposed to guide the USVs safely navigating in a cluttered environment. In addition, the formation forming problem has been specifically investigated with the algorithm being developed to make the USVs capable of forming the desired shape by following the trajectories from random initial configurations (positions and orientations). In order to eliminate the potential collision risks occurring on the route, a novel priority scheme based upon the distance to the closest point of approaching (DCPA) has also been proposed and developed. Algorithms have been validated on the computer-based simulations and are proven to work effectively in different environments

Autonomous Drone Landings on an Unmanned Marine Vehicle using Deep Reinforcement Learning

This thesis describes with the integration of an Unmanned Surface Vehicle (USV) and an Unmanned Aerial Vehicle (UAV, also commonly known as drone) in a single Multi-Agent System (MAS). In marine robotics, the advantage offered by a MAS consists of exploiting the key features of a single robot to compensate for the shortcomings in the other. In this way, a USV can serve as the landing platform to alleviate the need for a UAV to be airborne for long periods time, whilst the latter can increase the overall environmental awareness thanks to the possibility to cover large portions of the prevailing environment with a camera (or more than one) mounted on it. There are numerous potential applications in which this system can be used, such as deployment in search and rescue missions, water and coastal monitoring, and reconnaissance and force protection, to name but a few. The theory developed is of a general nature. The landing manoeuvre has been accomplished mainly identifying, through artificial vision techniques, a fiducial marker placed on a flat surface serving as a landing platform. The raison d'etre for the thesis was to propose a new solution for autonomous landing that relies solely on onboard sensors and with minimum or no communications between the vehicles. To this end, initial work solved the problem while using only data from the cameras mounted on the in-flight drone. In the situation in which the tracking of the marker is interrupted, the current position of the USV is estimated and integrated into the control commands. The limitations of classic control theory used in this approached suggested the need for a new solution that empowered the flexibility of intelligent methods, such as fuzzy logic or artificial neural networks. The recent achievements obtained by deep reinforcement learning (DRL) techniques in end-to-end control in playing the Atari video-games suite represented a fascinating while challenging new way to see and address the landing problem. Therefore, novel architectures were designed for approximating the action-value function of a Q-learning algorithm and used to map raw input observation to high-level navigation actions. In this way, the UAV learnt how to land from high latitude without any human supervision, using only low-resolution grey-scale images and with a level of accuracy and robustness. Both the approaches have been implemented on a simulated test-bed based on Gazebo simulator and the model of the Parrot AR-Drone. The solution based on DRL was further verified experimentally using the Parrot Bebop 2 in a series of trials. The outcomes demonstrate that both these innovative methods are both feasible and practicable, not only in an outdoor marine scenario but also in indoor ones as well