Robotic marine vessels can be used for a wide range of purposes, including defence, marine science, offshore energy and hydrographic surveys, and environmental surveys and protection. Such vessels need to meet a variety of criteria: they must be able to operate in salt water, and to communicate and be controlled over large distances, even when submerged or in inclement weather. Further challenges include 3D navigation of individual vehicles, groups or squadrons. This book covers the current state of research in navigation, modelling and control of marine autonomous vehicles, and deals with various related topics, including collision avoidance, communication, and a range of applications. It provides valuable insights for an audience of researchers, academics and postgraduate students interested in autonomous marine vessels, robotics, and electrical and automobile engineering.
Inspec keywords: path planning; marine navigation; mobile robots; autonomous underwater vehicles
Other keywords: unmanned surface vehicles; USV; autonomous marine vehicle communication; autonomous marine vehicle navigation; UUV; autonomous marine vehicle control; marine robotic vehicles; unmanned underwater vehicles; ocean resources
Subjects: Spatial variables control; Marine system control; General and management topics; Mobile robots
With the advance of artificial intelligence technologies, increasing deployment of autonomous marine vehicles is taking place especially in the application for executing demanding tasks. This chapter provides an insight into autonomous marine vehicles with a special focus on unmanned surface vehicles (USVs) and the design of an autonomous navigation system. After providing a general review on the development of USVs in both civil and military applications, methods employed for modelling and controlling USVs are specifically introduced and discussed. Particular interest has been cast on the motion planning of USVs with a series of simulation results presented to showcase the effectiveness of the autonomous navigation system in a practical maritime environment.
The objective of the path planning of marine vehicles is to determine a collision-free path from the start to the goal point in a practical marine environment comprising static and moving obstacles. A good number of path-planning approaches have been adopted from the area of mobile robotics and extended in the area of marine robotics. The current chapter overviews application of grid-based path planners in the area of unmanned surface vehicles (USVs). The current chapter also proposes a novel and computationally efficient approach towards optimal path planning of USVs.
This chapter presents an artificial potential field (APF)-based online collision avoidance system for manned and unmanned maritime vehicles, which is capable of reacting to static and dynamic obstacles in the vicinity. The standard marine `rules of the road' are integrated into the collision avoidance framework. A risk assessment module is also introduced which is based on the standard closest point of approach (CPA) method. A decision maker then selects appropriate rules based on relative heading and positions of the vessels. For the detection part, an integrated vision and laser-based system has been developed to provide sensing functionality for multiple obstacles. Autonomous craft are preferred over manned vessels in scientific operations as they are more suited for long enduring and tedious missions in dangerous or hazardous environments. The technique presented is fairly generic and is applicable to a general class of marine vehicles ranging from a small/medium-sized craft to a large freighter or an oil tanker. The small/medium-sized vehicles have been widely employed in surveillance and scientific missions. For surveillance missions, deploying autonomous vehicles will maximise the coverage and reduce the number of personnel involved in the operation area. Simulation results are provided to include the three fundamental collision encounter scenarios, that is, overtaking, head-on and crossing. It is also shown that Dubin circles could be successfully employed to take the dynamics of the craft into account, which provides a general method independent of the craft size.
This chapter presents a path planning algorithm for marine vehicles using the sliding mode paradigm to generate paths to a moving target point where it is required that the vehicle approaches the destination with a certain angle and proposes implementation of the guidance commands. In many underwater scenarios, information about the target point is unavailable after some time. These vehicles use sonar to extract the information, which fails as it comes close to the target. In such cases, the open-loop control method is the only way to reach the targets. A natural way of its implementation is sample and hold technique which do not yield satisfactory performance with its usual sampling method. This chapter proposes different sampling techniques to implement the guidance law in open loop. These methods are based on sampling the guidance command generated using closed-loop feedback with last known estimates about the target. To ensure robustness, a sliding mode control based impact angle guidance law is used. Performance of the guidance scheme using proposed sampling methods are evaluated through extensive numerical simulations for different engagement scenarios and shown to work well.
Operating a flight style autonomous underwater vehicle in close proximity to a terrain is very often completely reliant on the vehicle sensors for terrain detection. This challenges the manoeuvrability of such vehicles, which are also required to be energy efficient. In this chapter, recent experimentally based results on the performance of such vehicles are given. These results use the fully understood environment of a lake and are for the critical tasks of repeatability, obstacle detection and the actuation strategy used.
This chapter concerns about the design of nonlinear state feedback H∞ control algorithm for an autonomous underwater vehicle (AUV) for both vertical and horizontal planes which will lead to design a three-dimensional path following control. A three degree-of-freedom nonlinear model of an AUV has been considered in both horizontal and vertical planes for developing the diving and steering control laws, respectively. In this, the energy dissipative theory is used which leads to form a Hamilton-Jacobi- Isaac's (HJI) inequality. The nonlinear H∞ control algorithm has been developed by solving HJI equation such that the AUV tracks the desired depth and the desired yaw angle in diving and steering planes, respectively. Furthermore, the nonlinear control strategy has been extended for path following control algorithm in the steering. Simulation studies have been carried out using MATLAB®/Simulink® environment to verify the efficacies of the proposed control algorithm for AUV. From the results obtained, it is concluded that the proposed robust control algorithms exhibit a good tracking performance ensuring internal stability and significant disturbance attenuation.
This chapter proposes a real-time energy optimal trajectory planning and tracking method for an uninhabited surface vehicle (USV) in dynamically changing environment. The problem is first discretized by Legendre pseudospectral method to transform the trajectory planning problem into a nonlinear programming problem with less discrete points and higher accuracy compared with traditional discretization methods. Then a novel strategy is developed to re-plan the trajectory in real-time during the entire maneuvering. The re-planning strategy uses the values obtained in the last re-planning as its initial guess values and upper and lower bound, which can reduce the computational complexity dramatically. Simulation results show that this novel approach could save a considerable amount of equivalent energy compared with an existing traditional method.
This chapter introduces an event-driven, logic-based communication system for decentralized control of a network of nonlinear systems (agents) with the objective of driving their outputs along predefined paths at desired speeds, while holding a desired formation pattern compatible with the paths. An extended cooperative path following (CPF) framework is adopted where communications among agents take place at discrete time instants, instead of continuously. The communication system takes into account explicitly the topology of the communications network, the fact that communications are discrete, and the cost of exchanging information among agents. The theoretical framework adopted allows for the consideration of communication losses and bounded delays. Conditions are derived under which the resulting multi-agent closed-loop system is input-to-state stable, that is stable and with guaranteed levels of performance in the presence of bounded external disturbances and measurement noise. The set-up derived is used to solve the problem of CPF control of multiple underactuated autonomous marine vehicles. The results of experimental field tests with a group of marine vehicles are presented and discussed.
This chapter presents a brief review on numerous formation control strategies of multiple autonomous marine vehicle (AMV) such as autonomous underwater vehicle (AUV), unmanned surface vehicle (USV), surface vessels, etc. Classification of available formation control schemes for AMVs is presented that considers different structures, control strategies employed for formation, and coordination strategy. Advantages and disadvantages of the control strategies for multiple agents cooperative motion together with the network and communication issues in formation are also discussed.
This chapter describes the results of an easy-to-achieve implementation of an underwater acoustic (UWA) sensor network capable of operating in different modes for the exchange of UWA data among mobile and/or stationary network nodes that may include autonomous surface vehicles, autonomous underwater vehicles (AUVs), remotely operated vehicles, and benthic stations. The data exchanged are crucial in a number of applications that include cooperative multiple vehicle navigation and control, mission status assessment, and environmental sensing. A key novelty of the implementation described is the use of UWA modems incorporating the EviNS dedicated Networking Software Framework. The latter is a compact open-source, open-architecture software that is undemanding in terms of computer resources and can be installed directly on a UWA modem platform as part of its standard software. The practical usefulness and advantage of this solution stems from the fact that it significantly reduces the costs involved in setting up a UWA network while retaining small dimensions, small weight, and high energy efficiency of each hydro-acoustic network node (e.g. modems performing the functions of network communication devices). Several case studies with experimental networks based on UWA modems incorporating the EviNS Framework, with pre-installed but freely changeable mediaaccess and routing protocols, are presented in this chapter. Experimental results aimed at assessing the performance of the UWA network herein described are presented in relation to the combination of simple medium-access control protocols (providing uncoordinated access), wide-spread flooding-based routing protocols (based on so-called sequence number control), and polling protocols (implementing sequential and broadcast communications in networks with a centralized topology). Apart from providing details on the application of the EviNS Framework, the chapter offers a detailed analysis of the performance of an ad-hoc underwater sensor network operating in a shallow water area, i.e. in a hydro-acoustic environment of large practical interest. The chapter provides also a thorough analysis of the communication performance achievable with multiple nodes in a network with a centralized topology and affords the reader details of the practical estimation of the data rates achievable in communications involving multiple underwater modems performing simultaneous and asynchronous communications as elements of a mobile network. Even though the experiments reported were limited to specific cases, the number of network nodes used, the network geometries, and the fact that the underwater networks involved operated in complicated hydro-acoustic environments capture frequently occurring combinations of circumstances that occur in real off-shore practice.
Autonomous surface vessels (ASVs) have seen a rapid rise in their technical progress and capabilities, use cases and associated business models. This chapter discusses the current and emerging applications in three key sectors; i.e., defence, commercial and scientific. It includes a technology overview covering platforms, structures, energy systems, propulsion systems, internal sensors, external sensors, communications, processing, launch and recovery, auxiliary systems, remote operation centres and software. An overview of ASV types is provided covering different sizes and configurations and the chapter concludes with a look ahead to the future and how ASV technology may be applied in large sectors such as transport.
