Ideas for Underwater ROV Claw


#1

I’ve noticed that in many professional ROVs, they tend to only have one degree of freedom (opening and closing) for claws. Is there an advantage to this as opposed to building an underwater claw capable of 3 degrees of motion? (pitch, yaw and roll)

And in the context of manipulating objects (transporting items), is there a certain design that is both lightweight and strong that I could either buy or build?


#2

What are the advantages/ disadvantages of 1DoF vs 2, 3, 4, DoF claws? Well, cost is one obvious one - each actuator costs money. Whether the data chaneels can support the multiple DoF is another issues in complexity rather than cost. But reliability would be high up there too - each new actuator is one new device to fail, and at least two new electrical connections (actuator and position sensor) to fail, and probably penetrations into the electronics package.
Most of the work-class ROVs that I’ve seen (observed, but not really used) have only had 2.5 DoF - the claw could grip or ungrip; the claw’s mount could rotate 180deg in it’s mounting; the mount could be extended/ retracted on a line parallel to the other claw’s extend/ retract axis (the other claw normally being clamped on a grip point on the BOP. I believe this ROV (an Oceaneering one) could be fitted with a more sophisticated arm, but it would have needed a couple of days surface time to complete the change over once the parts, tools and spares arrived on the site. It was very much a “chargeable extra” to the contract, and the equipment was not provided to site to ensure that a rental and usage contract would be set up before they were dispatched to site. This is a business.