ROV manipulator to undergo further North Sea trials

Maestro tele-robotic hydraulic manipulator.

Shallow water ROV trials will be performed in the North Sea this autumn to assess the control system and NDT tool employed on the Maestro robot. Maestro is a modular, hydraulic manipulator developed by Cybernetix, Marseille arising out of its contribution to the 1991 REMO project co-sponsored by Elf and Phillips in Norway. Cybernetix designed and built the computer-aided robotic tele-manipulation system and automated inspection process used on the Stolt Comex Seaway ROV SCV REMO 1.

This was claimed to be the first ROV dedicated to IRM operations. It has since worked successfully on numerous projects on the Ekofisk, Frigg and Heimdal facilities. North Sea tasks last year included current output and wall thickness measurements; magnetic particle, eddy current and ACFM inspections; high pressure water jet and wire brush cleaning. These operations required advanced functions such as compliance, trajectory follow-up and 3D modeling techniques.

Following the REMO project, Cybernetix brought out its own version of the manipulator arm, Maestro, and the control system, named Compact. Six Maestros have been sold so far and it is currently being qualified for nuclear operations by the French Nuclear Committee. The system will be demonstrated this month at ONS Stavanger.

Maestro is made from titanium. Its position sensors are high accuracy, single-speed resolvers. Maximum lifting capacity is 100kg with the arm fully extended: there are seven degrees of freedom plus one optional (six axes + grip + tool changer). Dexterity is aided by the concurrent wrist design which allows the final segment to be particularly short: the axes of the three joints cross at the same point. Motion range of the wrist joints is 270.

Maestro's rotating hydraulic actuators have been designed to cater for a high level of resolution, precision and repeatability. Maintenance is straightforward: the actuators can be replaced within one hour. Four bolts ensure connection of the arm body to the actuators, with four more bolts connecting the actuator shaft to the next segment.

Connecting boxes are placed in all the segments so that electrical circuits can be easily disconnected. Cables and housings are located on the base of the arm to prevent problems with the cables when the manipulator is operating.

Last year Ifremer, which is also a partner in the REMO and Compact developments, performed external pressure tests on Maestro components at its test tank in Toulon. The actuators were pressurized at 600 bar for an extensive period. Ifremer has itself bought a Maestro manipulator, to be installed on its scientific research submarine Victor which can dive down to 6,000 metres.