Improving the Operability of Remotely Operated Vehicles

Underwater Remotely Operated Vehicles (ROVs) have a significant support role to play in offshore petroleum production facilities. The extent to which ROVs can replace diver-based operations depends significantly on ROV capacity and the relative costs of mobilising and implementing the two modes of underwater operation. This paper presents work directed at two aspects of ROV operability: the quality of visual information presented to the ROV pilots and the degree of station keeping control exhibited by the vehicle. Significant improvement in pilot performance of selected maintenance-type tasks has been achieved by the use of a purpose built underwater stereoscopic video camera and associated ship-based stereoscopic display unit. Two generations of cameras have now been built and used on a Perry Triton vehicle in use at the North Rankin A platform on the North West Shelf. In a related program, stereoscopic images of the platform structure are processed to determine the relative position of the ROV. Changes in position are used as inputs to thruster control algorithms, with a view to enabling the vehicle to hold position in fluctuating current fields. The position data from the processed 3D images are linked to output from an on-board inertial system to enable position to be maintained despite periodic loss of visual information. First trials of the combined vision-inertial system indicated some success, notably using the vision system, but indicated difficulties with the inertial package and its integration into the control process. An extension of this project is now being supported by the Australian Maritime Engineering Cooperative Research Centre (AME CRC).