Nicholas Townsend

Path Following of an Underactuated AUV Based on Fuzzy Backstepping Sliding Mode Control

This paper addresses the path following problem of an underactuated autonomous underwater vehicle (AUV) with the aim of dealing with parameter uncertainties and current disturbances. An adaptive robust control system was proposed by employing fuzzy logic, backstepping and sliding mode control theory. Fuzzy logic theory is adopted to approximate unknown system function, and the controller was designed by combining sliding mode control with backstepping thought. Firstly, the longitudinal speed was controlled, then the yaw angle was made as input of path following error to design the calm function and the change rate of path parameters. The controller stability was proved by Lyapunov stable theory. Simulation and outfield tests were conducted and the results showed that the controller is of excellent adaptability and robustness in the presence of parameter uncertainties and external disturbances. It is also shown to be able to avoid the chattering of AUV actuators.

Control Strategies for Marine Gyrostabilizers

This paper examines various control strategies for a marine gyrostabilizer system, including passive and derivative-based control methods and proposes two new marine gyrostabilizer control strategies: reaction wheel and unrestricted gimbal control. A numerical model is developed, and simulations of a 20-m monohull boat, in irregular beam waves, is presented, based on the control objective of minimizing the resultant excitation moments on the vessel. With limited literature on the subject of marine gyrostabilizers, this paper is intended to convey the state of the art, presenting the governing equations of motions, in addition to presenting new marine gyrostabilizer control strategies, which may be able to further improve their performance.

A Gyroscopic Wave Energy Recovery System for Marine Vessels

In this paper, a wave energy capture system for marine vessels is described. The system uses gyroscopic precession to create a relative motion within a vessel to generate power from the wave-induced roll and pitch motions. The governing equations of motion and a numerical model of the system are described in this paper and the behavior and performance of the system is identified. The system has several significant advantages over existing wave energy devices. For marine craft that operate in waves, the system could be very useful, providing a means to recover wave energy, reducing environmental impact, and improving operational effectiveness.

Gyrostabilizer Vehicular Technology

This paper examines the current state of gyrostabilizer vehicular technology. With no previous description of the wide range and variety of gyrostabilizer technology, this paper provides a review of the current state of the art. This includes a detailed examination of gyrostabilizer vehicular systems, dynamics and control. The present review first describes the historical development of gyroscopic systems before going on to describe the various system characteristics, including an overview of gyrostabilizer vehicular applications and system designs for land, sea and spacecraft. The equations of motion for generic gyroscopic systems are derived following momentum (Newton-Euler) and energy (Lagrange) based approaches and examples provided. The derivations are made generically for individual components, enabling direct application for a wide variety of systems. In the final section, a review of gyrostabilizer control strategies is presented and the remaining challenges are discussed. Gyrostabilizer systems are anticipated to become more widely adopted as they provide an effective means of motion control with several significant advantages for land, sea and spacecraft. (101 references)

What influences rigid inflatable boat motions

This paper presents results of full-scale and model-scale rigid inflatable boat (RIB) experiments identifying the influences of speed, ballast, wave height, encounter frequency, and tube pressure on the motion responses of Royal National Lifeboat Institution (RNLI) Atlantic RIBs. A discussion of the results and the influences on the motions is made with a description of the typical motion responses, measures to describe the motion, the function of a RIB tube, and the effect of the motions on the occupants.

Feasibility study of a new energy scavenging system for an autonomous underwater vehicle

Autonomous underwater vehicles (AUV) can only operate for hours or days at a time between battery charges. Alternative power systems or in-situ charging strategies are required to extend missions. This paper presents the feasibility of a new gyroscopic wave-energy scavenging system. The energy scavenging system promises to; reduce AUV battery requirements negating the necessity to carry sufficient energy reserves (size and weight) for entire missions, reduce costs by freeing support vessel time (a major cost component in AUV deployment) and enable AUVs to be remotely and renewably recharged at sea, indefinitely extending missions. A theoretical description of the system and simulation results for a range of geometrically scaled torpedo style AUVs are presented. The results show that the generated power is sufficient to provide power for a range of AUV sensors and comparable to equivalent solar panel and wind turbine devices.

Experimental analysis of submerged flapping foils; implications for autonomous surface vehicles (ASVs)

Autonomous surface vehicles (ASVs) have proven effective as ocean observing platforms for maritime operations. In most cases it is advantageous to operate ASVs for extensive missions in order to maximize their cost effectiveness. Such long endurance missions require ASVs to be capable of scavenging ambient energy from the surrounding ocean environment.

Hybrid renewable energy system for ocean going platforms

Renewable energy systems that extract power from sustainable sources such as wind, wave and solar can provide clean energy to a range of marine applications. Currently a major challenge is in providing an uninterrupted power supply, given the variation and uncertainty in these renewable energy sources. To deal with the unpredictable nature of renewable energy resources, this paper investigates the use of hybrid systems (systems that harvest multiple sources) to reduce the variation and uncertainty of the power generated. Considering the use of multiple renewable energy resources including solar, wind and wave, this paper first evaluates the available energy resources and the technical recoverable power using open-source, yearly, global, meteorological datasets. Based on the technical recoverable potential the complimentary features between solar and wind resources are investigated and compared to the propulsive power demand of various sized ocean going platforms and routes. The analysis shows that the resources can be complementary and that hybrid systems are more suitable for small vehicles, craft or maritime robotics system such as autonomous surface and underwater vehicles and oceanographic buoys.

In situ results from a new energy scavenging system for an autonomous underwater vehicle

This paper presents initial results from the first in-situ trials of a new gyroscopic energy scavenging system for an autonomous underwater vehicle.