Sean Nolan

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.

A low directivity ultrasonic sensor for collision avoidance and station keeping on inspection-class AUVs

This paper describes an ultrasonic sensor for integration on a UUV. The sensor is characterised by a wide-angle spatial transmission pattern, high range resolution, short minimum detection range and fast response time. For UUV operation in proximity to marine platforms, the seafloor or other hazards, sensors which have ranges below 2m with minimum detection ranges to a few centimetres are needed. Commercial sensors that adequately fulfil this role are as yet not available. The sensor presented has been designed to provide sensor coverage at these close ranges. It can be used to augment data obtained using conventional sonar and vision sensors in target applications such as station keeping, docking and close quarter’s collision avoidance.

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.

A novel wideangle ultrasonic sensor utilizing a curved radiator developed for use in an AUV obstacle avoidance system

This paper presents work on the development and testing of a wideangle ultrasonic transducer developed for use as a low cost short range obstacle avoidance system (OAS) on an autonomous underwater vehicle (AUV). The transducer design is novel in that it utilizes a commercial focusing-bowl piezo element as a convex curved radiator in order to achieve a wide-angled beam profile. The operating frequency of the piezo sensor has been selected to have a short wavelength in water yielding good range resolution. The dimensions of the experimental transducer are small and power consumption is low. It is proposed to use several sensors together with overlapping detection cones to build a sensing system that can provide useful information about objects in an AUVs environment. The principle advantages of such a sensing approach are that it would provide fast detection and location of close range targets and could be implemented with less hardware complexity and signal processing than a typical phased-array sonar approach thus reducing the overall system cost. The sound-pressure distribution, ultrasonic sensitivity, and pulse-echo acoustic performance of the transducer prototype are discussed. Water tank testing carried out to evaluate the acoustic response of the prototype in detecting various dimensioned reflectors in the laboratory is reported.

Implementing a Layered Control Architecture on an Open Framed AUV

Abstract Tethra is a prototype AUV, designed at the University of Limerick to carry out research in under water robotics and control. The vehicle adopts a behaviour based control paradigm. In this paper we report on the design and development of the Tethra test platform, its low-level control functionality and how this low-level control functionality is incorporated with in the robot controller. The functioning test platform is being used in ongoing research into controller development, investigating classical and neural network approaches. The vehicle is also being used for further behaviour based control development.

Integration and Testing of Multi-Purpose Platform Technologies System and High Resolution Multi-Beam Sonar on ROV Holland I

Abstract This paper describes the integration and testing of multi-purpose platform technologies system (MPPT-Ring), high resolution multi-beam sonar and state-of-the-art navigation system with the Ireland national work class ROV Holland I. In addition, the paper presents results of high resolution sea bed mapping along with the results of MPPT-Ring augmented reality support tools in offshore applications.