James Riordan

Implementation and application of a real-time sidescan sonar simulator

This paper describes the functional theory and design of a modular simulator to generate, in real-time, physically representative spatiotemporal sidescan sonar echo data. The seafloor topography is generated using fractal theory and the resulting terrain is tesselated into triangular facets. Propagation of the acoustic fan beam is determined by a ray theory solution of the governing wave equation while the contribution of each facet to the recorded intensity at the sonar transducer is resolved by applying Jacksons seafloor scattering model. The computational bottleneck inherent in the discovery of illuminated facets at each ping is significantly reduced by the implementation of an optimised mesh refinement scheme intended for interactive rendering of large-scale complex surfaces described by polygonal meshes. The resulting performance increases enabled the successful integration of the sonar simulator with an existing AUV simulator. Synthetic images and the performance measures of the sidescan simulator image generation are presented.

A Flexible Multi-Mode of Operation Survey Platform for Surface and Underwater Operations

Abstract This paper describes a novel vehicle designed for operation flexibility in high-resolution near seabed survey from shallow inshore waters out to the continental shelf edge. The vehicle can be operated in surface tow or as a thrusted pontoon. With buoyancy module release the vehicle becomes neutrally buoyant and is operated as a survey class remotely operated vehicle (ROV) depth rated to 1,000m. Special features of the system include: deployment interoperability for small inshore boats and larger research vessel; fault tolerant thruster control; novel high frequency short range sonar; onboard computer control enabling real-time disturbance reaction; topside augmented reality system support etc.

Automated Optimisation of Simultaneous Multibeam and Sidescan Sonar Seabed Mapping

With the costs involved in offshore seabed mapping being very large and dominated principally by the expense of survey vessel time, any improvement in the planning and execution of seabed mapping, improvement in the quality of the resulting data, and especially reduction in survey costs are of significant interest to the marine and offshore community. This paper presents a terrain adaptive seabed mapping system, which simultaneously operates co-located high-resolution multibeam and sidescan sonar of similar frequency. The automated system is based on the interleaving of sonar transmission-reception cycles to avoid interference. The proposed system optimises the execution of the seabed mapping survey, improves the quality of the data and reduces survey costs.

Multi-mode Operations Marine Robotic Vehicle – a Mechatronics Case Study

This chapter details the development of a novel, multi-mode operation marine robotics vehicle designed using mechatronic principles for operational flexibility in high-resolution near-seabed surveys from shallow inshore waters out to the continental shelf edge. The vehicle can be operated in surface-tow mode or as a thrusted pontoon. With the buoyancy module released, the vehicle becomes neutrally buoyant and is operated as a survey class remotely operated vehicle (ROV) depth rated to 1,000 m.

Real-Time Adaptive Control of Multiple Colocated Acoustic Sensors for an Unmanned Underwater Vehicle

In this paper, a novel approach to provide full autonomy in the control and synchronization of multiple payload sonar systems is described, facilitating the close-proximity integration and concurrent operation of multiple high-frequency acoustic sensors on an unmanned underwater vehicle. Recent advances in computational technology and real-time programming techniques afford the ability to process bathymetric data in situ to react to real-time environment data. The novel approach presented interrogates real-time bathymetric data to predict the transmission-reception timing of payload sensor acoustic pulses, thus permitting the ability to synchronize the trigger of the instruments such that neighboring return signals of other sonar are not saturated by sensor crosstalk.

Terrain-adaptive ping sequencing of UUV integrated multibeam echosounder and sidescan sonar systems

This paper presents an approach to the terrain-adaptive control of multiple acoustic sensors integrated onto an Unmanned Underwater Vehicle (UUV). In-mission processing and analysis of bathymetric data allows the system to synchronise the transmit-receive cycles of multiple sonar systems in a non-interfering fashion. By dynamically adapting the triggering of the payload sensors, the system optimises the execution of the seabed mapping survey and improves the quality of resulting data, thereby significantly increasing survey productivity. An examination of state-of-the-art in UUV control is examined in the context of sensor payload management.The systems features, design and implementation are presented, as well as a discussion and detailed analysis of at-sea trials.

A Real-Time Subsea Environment Visualisation Framework for Simulation of Vision Based UUV Control Architectures

Abstract The simulation requirements of UUV visual-based technology points toward a readily available candidate solution in the form of modern 3D graphics rendering technology, which has the capability to generate photorealistic representations of synthetic subsea environments in real-time. This paper describes the ongoing development of a simulation platform for synthetic seafloor terrain generation and visualization. Originally designed as an operator aiding-tool to provide improved situation awareness through visual immersion in the mission scenario, it is intended to use the augmented reality display representing the onboard camera to support the continued appraisal of a real-time vision-based UUV navigation system currently under development within the Research Centre.

INTEGRATED CONTROL OF MULTIPLE ACOUSTIC SENSORS FOR OPTIMAL SEABED SURVEYING

Abstract This paper presents an integrated acoustic controller system which processes multibeam data in real-time to provide a priori bathymetry data to auxiliary acoustic sensors facilitating the operation of co-located, similar frequency sonar. The automated system is based on the interleaving of the sonar transmission-reception cycles to avoid cross-sensor acoustic interference. By dynamically adapting the ping rates of the payload sensors, the system optimises the execution of the seabed mapping survey, improves the quality of the resulting data and reduces survey time and costs.

Approach to the Real-Time Adaptive Control of Multiple High-Frequency Sonar Survey Systems for Unmanned Underwater Vehicles

Abstract This paper presents an approach to the real-time adaptive control of multiple high-frequency sonar for Unmanned Underwater Vehicles (UUVs). The central acoustic sensor controller manages the sensors during survey missions, facilitating the operation of co-located, similar-frequency sonar. Multibeam data is processed in real-time to provide a priori bathymetry data to auxiliary acoustic sensors. The automated system is based on the interleaving of the sonar transmission-reception cycles to avoid the saturation of acoustic harmonics, permitting the integration of multiple acoustic sensors operating in parallel. By dynamically adapting the ping rates of the payload sensors, the system optimises the execution of the seabed mapping survey and improves the quality of the resulting data, thereby significantly increasing survey productivity.

Experimental setups for vision-based navigation of unmanned underwater vehicles in near intervention operations

Abstract In the last decade, vision systems have become an instrumental sensor in the development of accurate control and navigation systems for unmanned underwater vehicles. Unfortunately testing of new vision based techniques in actual underwater environments is a difficult and expensive proposition. This paper details the development and evaluates the potential performance of two novel methods for underwater vehicle vision based control and navigation systems testing; physical simulation and virtual simulation. The paper also details the experimental setup for test tank trials utilizing a seabed poster representation. This setup is evaluated based on results from a previously developed real-time vision based navigation system. The experimental setup for sea trials of the University of Limericks newly developed thrusted pontoon/ROV is also presented.