Sunday, May 19, 2019
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La Spezia - SURVEY OBJECTIVES

During the various demonstrations of the CMRE external system guidance using the Catamaran Autonomous Surface Vehicle (ASV), the VIP visitors had questions about the robustness of the ASV system. The response of CMRE research team has been that the ASV is used as a modified commercial off-the-shelf (COTS) platform of opportunity with operation limitations in higher sea state and an inability to work with targets at greater depths. However, the concept and the algorithms are not specifically linked with the demonstration platform and can easily be ported onto any other platform. The objective of ANT’12 (Part 2) was to gain results that will convince the operational community that the concept works in more difficult conditions.  

THE CMRE research team established collaboration with the Mobile & Marine Robotics Research Centre (MMRRC), University of Limerick, led by Dr Daniel Toal. Over the last seven years, the MMRRC research team has developed a set of smart technologies for subsea operations, collectively known as OceanRINGS.  A major component of the system, designed as a prototype platform to demonstrate system validity and operability and to prove new technologies, is a smart survey class remotely operated vehicle, ROV LATIS. It is a next generation smart ROV with unique features, including multiple modes of operation, advanced 2D and 3D displays, built-in fault-tolerant control system and intuitive, versatile and easy to use pilot interfaces with full autopilot capability. Use of the ROV LATIS extended ANT’12 project’s objective outputs and successfully demonstrated the external guiding concept in environmental conditions equivalent to the conditions of current mine disposal operations.

NATO Science and Technology Organization - Centre for Maritime Research and Experimentation (CMRE), University of Limerick (UL) and University of Zagreb (UZ) collaborated during Autonomous Neutralization Trial (ANT'12) Part 2 sea trials, held in the coastal waters of La Spezia, Italy, in the period 17 Oct - 07 Nov 2012. The Autonomous Neutralisation Trial was performed as one of the objectives of the Autonomous Naval Mine Countermeasures Programme (ANMCM) which has a goal to achieve the entire chain of Mine Countermeasures Programme (MCM) using unmanned, robotics platforms.

The focus of the project is to perform reacquisition, identification and neutralisation using a pair of underwater vehicles: ROV LATIS (UL) as external support platform (guiding platform) and automated ROV (aROV) GOLDRAKE (CMRE) as a miniature underwater vehicle (guided platform). Collaborative multi-national sea trials allowed for the congregation of expertise and robotic systems from various institutions worldwide. Objectives included precision guiding of an inexpensive underwater vehicle to an underwater target using the navigation suite and control system of a more capable underwater vehicle. These objectives were realised and the researchers' opinion is that the extension to multi-vehicle cooperation (one leader guiding several agents, followers) is feasible given the test results.

Dual acoustic modem capability

The robust acoustic communication system, used to send navigational updates from the topside to the inexpensive aROV has been previously tested in numerous sea trials. ANT’12 Part 2 trials focused on extending the already tested and proven solution to include two-way communication, i.e. to modify the existing acoustic link such that a target image can be sent from aROV to the topside through acoustic modem installed on ROV LATIS. This task is to be completed after the arrival of the guided robot (aROV) to the target. In this way an external support platform (ROV LATIS) is used as a communication relay for the identification image to be forwarded to the commander prior to the neutralisation.

Guiding the aROV to the target at depths of up to 80msw using HiPap USBL system
This objective had a focus to show the extended utility of external navigation algorithm. When the aROV is out of the range of the forward looking (FL) sonar, it can be localised by another acoustic positioning system (USBL). Although the navigation accuracy of the aROV 3D path following in this case is not as good as when the FL sonar is used, (since the measurements are more sporadic and less accurate), this approach can be used for guiding over extended distances far away from the target. Once the aROV arrive inside range, the FL sonar can be used for precision guiding to the target. This objective is similar to objective #3 from Part 1, but the range & bearing information comes from the USBL system.

Guiding the aROV to the target at depths of up to 80 using ROV LATIS sonar
The objective is to exercise the CMRE guiding software with another external support platform (ROV LATIS) carrying the FL sonars (RESON and BlueView) – this platform has not been tested previously. The non-conventional underwater navigation concept and algorithms for MCM have been tested before using different external support platforms (CMRE Gemellina Catamaran ASV and CNR's Charlie ASV). The main limitation of these platforms is inability of their control systems to independently control course and heading (due to under-actuated thruster configuration – the platforms do not have lateral thrusters) and inability to operate in greater depths i.e. only surface-bounded operations  are possible. ANT’12 Part 2 sea trials have a primary objective to extend the usability of these algorithms to 3D, where both the guiding platform and the guided platform can move in 3D space.

REPORT / ACHIEVEMENTS

The Operational Area is within the “Parco Nazionale delle Cinque Terre” – 0.3 nm around C80 point (N 44 04.550, E 09 40.675), inside CMRE berthing area and outside the CMRE waterfront.



13th - 16th Oct: OceanRINGS System Core was integrated with CMRE software in Virtual Environment (Dula Nad, Gabriele Ferri & Edin Omerdic). Dynamics of Virtual ROV LATIS and virtual ship LEONARDO were simulated in different sea states and time-varying ocean currents. Sonar simulation and aROV GOLDRAKE dynamics was simulated with CMRE software. Data exchange link was realized through software architecture “Mission Oriented Operating Suite - Interval Programming “(MOOS - IvP), developed by the Mobile Robotics Research Group at Oxford University, the Computer Science and Artificial Intelligence Lab and Dept. of Mechanical Eng. at MIT, and the Naval Undersea Warfare Centre in Newport Rhode Island (NUWCNPT).


MOOS Interface integrated in ROV LATIS Pilot Interface application
Toggle button “MOOS Enabled” serves as a software switch to select who has a direct control of ROV LATIS. An enabled state confirms that the Command Centre has direct control of the ROV. Depending on a state of the mission, Command Centre sends commands to ROV LATIS to change/keep depth, keep distance from aROV/Target etc. Also, when disabled, LATIS ROV pilot regains direct control. In normal situation ROV pilot will take control after the mission is completed. However, ROV pilot continuously monitors mission progress and can interrupt the mission execution and take control at any moment if something goes wrong.


16th - 17th Oct: Virtual Reality model of ship LEONARDO was converted from 3D Studio format to VRML format (Dula Nad) and integrated within OceanRINGS (Edin Omerdic). The VRML format was used later for 3D real-time visualisation of mission progress.



14th - 17th Oct: Integration of the LATIS control cabin, winch and ROV took some time as CMRE inspections and checking of certification called for additional welding and inspection/certification before clearing ROV Latis systems for secure use aboard CRV Leonardo’s deck. Once the equipment was on board, integration with the ship (electronics, communications) began and was completed a day later. Following this, ROV LATIS was deployed in dock to a depth of 2 metres when some short circuit faults presented.  The ROV was recovered for test and repair. Testing took some considerable time to isolate the root cause of the faults and found a faulty thruster as well as a flooded thruster bottle bulkhead connector cable assembly (possibly damaged during transport). The faulty thruster was removed from the ROV for all subsequent tests and the CMRE workshops improvised a thruster bulkhead connector replacement. The Sea borne testing began following the repairs and subsequent integration.



Over a number of days CRV Leonardo departs from CMRE berthing area, transits to the experimental site, performs standard operations and attends deployed ROV systems, and returns to the CMRE berthing area. ROV LATIS and aROV GOLDRAKE were deployed and performed operations in the designated area. The CMRE rubber boat support was available at all times for assisting the operations and warning the nearby vessels.

Operations began on Oct 18 with the target deployment. Due to the hardware problems described above in the previous section, several first days were lost. On Oct 22 the target was deployed in the main operational area in Cinque Terre. The following days were used for autonomous mine neutralisation missions using the ROV LATIS and aROV GOLDRAKE systems. Various ROV LATIS behaviours were performed and sonar data collected. Post-processing and data quality checks took place in the Leonardo lab.

Shown below are the results obtained during one of the experimental missions.

Two state-of-the-art forward looking sonar (FLS) imaging systems were mounted onto LATIS over the course of the experimental operations. These systems include the P900 from Teledyne Blueview and the 7128 SeaBat from Reson.

The P900, operating at 900 KHz, constructs 256 beams (synthetic) into a 90 degree swath fan beam and is capable of producing an image map with range resolution of 25.4mm. The P900 comes in a small lightweight package and is relatively low cost. The SeaBat 7128, operating at 400 KHz, constructs 256 beams, 128 degree swath, is capable of a finer range resolution of approximately 6mm and the imagery is clearer out to longer ranges up to 100m. On the other hand the 7128 comes at a higher cost and is significantly larger in size.


Both systems were mounted on the front of ROV Latis and used to collect datasets during ROV missions enabling simultaneous acquisition. This allowed for high resolution imagery of the surrounding environment including (aROV and Mine / cylinder target) up to 50m distant for P900 and greater ranges up to 100m distant for the Reson 7128. 

Detection of submerged objects such as debris (various), aROV GOLDRAKE, MCM targets (cylinders) and harbour installations (walls, anchors etc) became easily viable. In addition, surface objects such as ship and Rhib hulls as well as propeller wake (bubbles) were also identifiable in these datasets. 


The first image is taken in 9 MSW while the second one is taken in 80MSW. Distance scales are as follows (max point) – 7128 is 50m in image1 and 75m in image2, P900 is 40m in image1.


The third image above shows the target at 68 metres distant from LATIS and the aROV at 30 metres distant. The shape of both objects is clearly identifiable from the returned data, the signal strength of the sonar returns gives an indication of composition and the shadow from the return gives an indication of height from the seabed.

This shows the capability of the Reson 7128 forward looking sonar imaging system in terms of identifying targets at significant distances from the sonar head. The data received from the Blueview sonar was not capable of identifying the target at this distance.


The image above shows the data captured during a deep water mission in a depth of 80 MSW over a rocky seabed. Two targets were deployed at this site, the cylinder target and a large 1 Tonne rock. 

Again, the capability of the forward looking sonar imaging system is demonstrated. The data received shows a stronger return from the seafloor. However, shape and identification of each of the targets are easily resolved even at extended depths.