Design and Control of a Flight-Style AUV with Hovering Capability

The small flight-style Delphin AUV is designed to evaluate the performance of a long range survey AUV with the additional capability to hover and manoeuvre at slow speed. Delphin’s hull form is based on a scaled version of Autosub6000, and in addition to the main thruster and control surfaces at the rear of the vehicle, Delphin is equipped with four rim driven tunnel thrusters. In order to reduce the development cycle time, Delphin was designed to use commercial-off-the-shelf (COTS) sensors and thrusters interfaced to a standard PC motherboard running the control software within the MS Windows environment. To further simplify the development, the autonomy system uses the State-Flow Toolbox within the Matlab/Simulink environment. While the autonomy software is running, image processing routines are used for obstacle avoidance and target tracking, within the commercial Scorpion Vision software. This runs as a parallel thread and passes results to Matlab via the TCP/IP communication protocol. The COTS based development approach has proved effective. However, a powerful PC is required to effectively run Matlab and Simulink, and, due to the nature of the Windows environment, it is impossible to run the control in hard real-time. The autonomy system will be recoded to run under the Matlab Windows Real-Time Windows Target in the near future. Experimental results are used to demonstrating the performance and current capabilities of the vehicle are presented

Reliability Case Notes No. 4: Autosub6000 and Autosub3 actuator potentiometer failure analysis and testing report

During the James Cook Cruise 27 Autosub6000 aborted mission 12 due to a failure in the position feedback potentiometer of the stern plane actuator. The same actuator is used on Autosub3 which is heading to the Pine Island glacier in Antarctica in January 2009. A similar failure of the Autosub3 actuator while under the ice would result in the loss of the AUV.This report initially describes the investigation into the failure of the feedback potentiometer and shows that the potentiometer’s conductive plastic track became detached from its ceramic substrate and broke up. The report then describes the testing performed to evaluate the reliability of the potentiometer. This involved an accelerated aging test to simulate the worst case conditions seen by the potentiometer in the actuator. This was achieved by oscillating the potentiometer at 4Hz to simulate the actuator movements whilst cycling the pressure of the Morlina 10 oil surrounding the potentiometers.During the testing the 10k? potentiometers used in the actuator were not available, and so 5k? potentiometers from the same range were tested as a substitute. It was assumed that these 5k? potentiometers would produce similar results, however it was found during the testing that the formulation of the 5k? potentiometer track was different from the 10k?; whether this affects the reliability is not known.Due to the large amount of time required to perform each test only 16 5k? potentiometers were tested. Although no failures occurred, the sample was too small to give a high statistical confidence that the potentiometers would survive the cruise. To further reduce the risk four 5k? potentiometers that were to be used on Autosub3 were tested for approximately 72 hours in a ‘burnt in’ process. As an early failure similar to that of Autosub6000 potentiometer would have been detected during this process, the chance of the potentiometers failing was significantly reduced. Thus the burnt in potentiometers were considered acceptable for use on Autosub 3 during the Pine Island campaign

Evaluation of manoeuvring coefficients of a self-propelled ship using a blade element momentum propeller model coupled to a Reynolds averaged Navier Stokes flow solver

The use of an unsteady computational fluid dynamic analysis of the manoeuvring performance of a self-propelled ship requires a large computational resource that restricts its use as part of a ship design process. A method is presented that significantly reduces computational cost by coupling a blade element momentum theory (BEMT) propeller model with the solution of the Reynolds averaged Navier Stokes (RANS) equations. The approach allows the determination of manoeuvring coefficients for a self-propelled ship travelling straight ahead, at a drift angle and for differing rudder angles. The swept volume of the propeller is divided into discrete annuli for which the axial and tangential momentum changes of the fluid passing through the propeller are balanced with the blade element performance of each propeller section. Such an approach allows the interaction effects between hull, propeller and rudder to be captured. Results are presented for the fully appended model scale self-propelled KRISO very large crude carrier 2 (KVLCC2) hull form undergoing static rudder and static drift tests at a Reynolds number of 4.6×106 acting at the ship self-propulsion point. All computations were carried out on a typical workstation using a hybrid finite volume mesh size of 2.1×10^6 elements. The computational uncertainty is typically 2–3% for side force and yaw moment.<br/

Accurate capture of rudder-propeller interaction using a coupled blade element momentum-RANS approach

Ship rudders are almost always placed downstream of the propeller so they can take advantage of the increased local velocity due to the presence of the propeller race. The methods discussed in this paper replicate the flow integrated effects of the propeller which generates an accelerated and swirled onset flow onto the rudder. As long as the radial variation in axial and tangential momentum (including hull and rudder interaction effects) generated by the propeller are included, then the influence of the unsteady propeller flow can be removed and ’steady’ calculations performed to evaluate propeller rudder interaction. Three different body force propeller models will beconsidered and numerical results will be compared with experiments by Molland and Turnock [1, 2, 3], using the modified Wageningen B4.40 propeller and Rudder No.

A New Collision Avoidance System for the Autosub6000 Autonomous Underwater Vehicle

The recently developed Autosub6000 Autonomous Underwater Vehicle (AUV) is the latest in the Autosub series of AUVs that have been built at the National Oceanography Centre, Southampton. The previous AUV have been deployed on numerous science missions over the last decade. Autosub6000, with its 6000m depth capability, is currently in demand for deep ocean bathymetric surveys using its Simrad EM2000 multibeam sonar system. However, the terrain that can currently be surveyed is limited due to the lack of an obstacle avoidance system. In order to survey rugged and challenging regions a new obstacle avoidance system is being developed. This system uses a Tritech Seaking mechanically scanned sonar system oriented to scan vertically in front of the AUV to provide details of obstacles as well as changes in terrain. This paper describes the obstacle avoidance approach adopted and outlines its implemenation within Autosub6000. Simulation outputs showing the performance of the system are presented and results from trials of the Tritech Seaking sonar are also given

Nonlinear system identification tools applied to the modeling of submarine dynamics

This paper presents initial work on the system identification of hydrodynamic coefficients used in fully coupled, non-linear submarine motion equations. The identification processes uses the sequential quadratic programming technique. The paper briefly describes the form of the non-linear equations use in the submarine simulation, outlines the system identification technique used and concludes by considering three identification cases. These cases are based on horizontal motion only and try to identify the coefficients assuming they are completely unknown, partially known and partially known but with an error on the known values

Autosub Long Range: A long range deep diving AUV for ocean monitoring

This paper introduces the Autosub Long Range Autonomous Underwater Vehicle being developed at the National Oceanography Centre, Southampton. This propeller driven vehicle is designed to have a 6000m depth rating and a 6000km range. This is achieved by reducing the propulsion power by travelling slowly and hotel power by careful component selection and husbanding of resources. The challenges associated with net buoyancy compensation and low Reynolds number phenomena are outlined, and a passive compensation scheme is described. Early field trials are discussed, and the AUV's role in the upcoming FASTNEt science programme is outlined

Metal-Affinity Separations: A New Dimension in Protein Processing

Rapid growth in the preparative and high-resolution analytical applications of metal-affinity chromatography demonstrate the appeal of metal recognition as a basis for protein separations. Stable, inexpensive chelated metals effectively mimic bio-specific interactions, providing selective ligands for protein binding. This article reviews recent progress in understanding the mechanisms of metal-protein recognition that underlie metal-affinity separations. Also discussed are schemes for integrating metal-affinity purifications into the expression and bioprocessing of re-combinant proteins. Promising future developments include new metal-affinity processes for analytical and preparative-scale separations and a range of techniques for enhancing the selectivity of metal-affinity separations