Designated the ARM 5E, it uses oil filled motors that are pressurised to slightly above ambient. These can be mounted in the same footprint as a hydraulic arm, but because they are electric, they don't require the use of a skid, valve pack or hydraulic pump. This reduces weight and allows greater vehicle manoeuvrability. It is also much more precise than most fluid powered devices, and with digital positional feedback, can be made to work to an accuracy of better than 0.5mm. Managing director Simon Gilligan says: "A 0.4bar over pressure is maintained against external pressure by connecting the cavities containing the oil to a vessel with a spring loaded plunger. "They are brushless motors from two suppliers. We modified them fairly heavily to suit the application and used some very specialist components." The arms are primarily intended to be used on remotely operated vehicles and autonomous underwater vehicles but can also be mounted on human operated submersibles.
Pressurised motors replace hydraulics underwater
CSIP in Weymouth has developed an all-electric, five-function, manipulator arm for underwater vehicles, rated down to depths of 3,000m.
