The Portroe Trial focused on three ocean engineering /technology objectives relevant to MMRRC research within the SFI REsearch Centre, Marine Renewable Energy Ireland (MaREI). At MMRRC we are addressing the need for ROV systems capable of performing Inspection, Repair & Maintenance on subsea infrastructures in harsh sea conditions. That is why we were testing: advances manipulator controls, smart navigation & pose estimation, and pressure and motion reference sensor.
The operation was mobilised on Monday, 21st November in Portroe Quarry in Tipperary, Ireland. The flooded quarry offered great conditions for first testing our developed systems: 35m water depth, and clear and calm water. The quarry ceased operation in 1956, and was flooded in the following years. Today, it is used as inland scuba diving centre for training and recreational use.
During the first day, once all the equipment arrived from P&O Maritime facilities in Galway, we set it up and finalised integrating the UL equipment :mounting of the UL Schilling Titan Manipulator, REson 7128 forward looking sonar, Blueview P900-2250 forward looking sonar and machine vision cameras, much of which was already completed prior to the mobilisation. An aluminium platform with a number of valve stations was deployed on a flat area of the quarry bed, to be used for intervention tasks. During the trial we deployed a VideoRay to gave us a live video of what is happening under the surface.
Advanced Manipulator Controls
Over the last year, we have reconfigured a standard Schilling T2 Manipulator control system, adding a computer based control solution with full kinematics engine for control of the manipulator alongside the standard master arm control approach employed in the offshore industry. Additionally, we have developed fully autonomous control for challenging intervention ops. During the Portroe offshore trial we completed the validation of the advanced motion control system for subsea manipulators through completion of a pre-defined list of subsea tasks, such as: replacing a valve T-bar, moving a rope which was in front of the frame to a position behind it, and turning the valve T-bar. We believe that using the developed software would help ROV pilots to execute typical subsea manipulation tasks easier, faster and more accurately. The videos below show two of the mentioned tasks, for more videos visit out Vimeo Channel.
Smart Navigation & Pose Estimation
Having a 3D model of your surroundings in real-time and knowing the exact relative position of the ROV relative to it opens a very large number of possibilities for task automation, augmented reality for ROV pilots, and site documentation. At MMRRC, we are developing a novel system for real-time 3D reconstruction and tracking of a targeted structure based on camera systems and aided through sonar and inertial navigation systems. This system was trialled at Protroe using the existing submerged objects as target scene. Portroe quarry, being used as an inland recreational dive site, is full of interesting objects, one of which is a submerged bar with a number of manikins and other objects propped up next to it. We took a video footage of the this bar and ran the UL 3D reconstruction system, rendering a 3D scene, meanwhile, sonar system was gathering data that can be used for correcting small errors in the tracking and reconstruction quality. Once the 3D reconstruction is complete, the distance and pose to any pixel within the scene can be estimated with a high degree of accuracy. This information is vital to performing automated intervention tasks and can be used for base vehicles control relative to target in a variety of operations from automated pipeline surveying to offshore infrastructure inspections.
Pressure and Motion Reference Sensor
A novel optical fiber sensor for high resolution underwater pressure & temperature measurement was also tested in Protroe. A similar sensor has been successfully developed and tested for biomedial and geotheral pressure sensing and is covered by patent. This sensor is robus and extremely small, fabricated entirely from Silica glass, and has a very high resolution. It was housed in a subsea enclosure and powered by on-board lithium batteries. The whole system was mounted on the base frame of Holland I ROV and recorded temperature and pressure throughout the day. the image below shows the recorded pressure for one of the operation days.