The project is aimed at performing the sea trials of an innovative underwater supervisory controlled telemanipulation system to verify in the real operative scenario, its performance and operative efficiency.
The system has been developed by Tecnomare within the research project "Underwater telemanipulation system whith supervisory control for inspection and maintenance of offshore installations" as a part of the contract TH/07061/86.
The first part of the project allowed the realization and integration of all the elements needed to provide a ROV with advanced telemanipulation technologies, obtaining a system composed essentially of two distinct "modules", namely:
- a "skid" containing:
* the tools (with stow units)
* the manipulator
* the TV-trackmeter
* the docking arm
* the attitude sensors
* the control electronics and
* the pack of electrovalves
- a control console with:
* supervisory control system
* joystick and touch panel for the supervisor
* navigation control system with control push-button panel
* TV-trackmeter surface unit with monitor
* computer and monitor for the graphic simulation system.
The system is composed of industrial type components and equipment suitable for operative use in the field for effective interface with a commercial vehicle. Furthermore, the substantial work on the development of software, carried out in parallel with design and construction, has produced a series of packages which have proved to be fully satisfactory.
The second part of the project, concerned with the carrying out of tests, has achieved various objectives in subsequent stages: initially the integration tests have allowed to check successfully the functional behaviour of the various sub-systems which were transferred during the project from the laboratory versions to the versions suited for work in operative conditions.
Subsequently the system has been integrated with a commercial ROV and the inspection and maintenance tasks were experimented in pool trials. To do this the system was subjected to a long series of tests to check the performance with the variation of the three following conditions (in different combinations): station keeping techniques, ROV control methods, operations on a node or on a subsea plant.
Finally all the most demanding tasks contemplated by the project aims were experimented, building up considerable operating experience and showing the validity of the system choices although it was not possible to perform trials at sea. The most important technical results may thus be summarised as follows:
- loose docking is the most promising way to achieve the performances requested
- the accuracy of the manipulator proved to be a critical element for performing the most delicate tasks
- the use of the TV-Trackmeter for the scene reconstruction proved to be valid also in visibility conditions that might appear prohibitive; vice-versa it should be noted that its use as an instrument to measure continuously the coordinates of the vehicle with respect to the node requires further improvements.
The tests carried out have allowed to experiment successfully and widely the supervisory control capacities as we had intended when setting the aims of the project; it was possible to achieve these in working conditions completely comparable with those met when carrying out campaigns on a platform and on subsea systems.
The Telemanipulation System is based on the supervisory control telemanipulation concept : a surface operator commands a remote arm through a supervisory computer that takes care of man-machine interfaces, allowing :
- perception of the scene : a television picture supported by
three-dimensional graphic displays which permits the observation of
the scene artificially from different points of view
- operations : the operator's commands are decoded by computer and then
sent to the telemanipulator.
In this way it is possible to observe the scene and to perform various tasks by operator single commands. In addition, it is possible to command in real time by joy-stick the same remote arm's freedom degrees automatically selected and controlled by the computer on the basis of the task to be executed.
The sea trials project continues this research line aiming at verifying the performances of the supervisory controlled telemanipulation system in the real operational offshore scenario. In particular the following items will be checked :
- cost reduction in inspection and maintenance operations with respect
to divers' use;
- increase of safety in underwater operations in relation both to the safety
of persons (substitution of divers) and of that of plants (inspection and
maintenance operations constitute a key factor for the increase of
installations safety);
- increase of operative efficiency with respect to divers' or conventional
direct control telemanipulation systems;
- system capability to operate in accordance with the requirements of
the existing international rules.
Two kinds of trials are foreseen involving two different operational scenarios :
- non-destructive testing of offshore platform nodes
- light maintenance operations on underwater well heads or subsea
production systems.
It is foreseen, in the second case, to experiment also simple manipulation operations where the carrier ROV is not docked to the plant structures but is automatically hovering in front of them.