Page 508 - The ROV Manual - A User Guide for Remotely Operated Vehicles 2nd edition

divers began to accept these mechanical intruders, and their reliability began to increase, they became an essential part of work operations. Whether providing topside operators with real-time feedback on the status of the underwater work or bringing down or retrieving tools, they expanded their roles offshore (Figure 19.2). As offshore operations slowly moved into waters beyond diver depth, the ROVs increased their manipulative capabilities. When the oil companies realized that remote intervention was the future, they finally began working with the ROV developers to configure the underwater equipment and tasks to be handled remotely.
The earliest ROVs had no more than a gripper attached to them, which essentially made the ROV a “flying hand.” This flying hand was essentially the manipulator; it had the number of degrees of freedom (DoF) that the thrusters could provide, which was rather limited. The vehicle also had to deal with the inhospitable ocean environment that often included adverse currents, wave dynamics and poor visibility. By adding a more capable manipulator with more DoF to a free-flying ROV, the manipulative options increased, but the operator now had to deal with the manipulator’s dynamics as well as the vehicle’s motion. Enter a second manipulator, one with fewer DoF, that could grab onto or mate with the object to be worked on, and the operator began to get a more stabler, or more structured, work environment. Thus the standard design of work- class vehicles, from lightweight to heavy duty, includes two grabbers/manipulators.
As ROVs replaced divers in more areas, especially in environments hazardous to divers, the desire to retain the diver’s manipulative capability always remained. Designers have continued to develop various versions of anthropomorphic manipulators that provide the topside operator with an ability to conduct manipulative operations as if the operator were using his/her own arms. This capability, known as telepresence, has seen wide research. As an example, research conducted by the US Navy (Figure 19.3) used such a system that also included binaural hearing and stereo vision. The operator wore a helmet that was used to move the underwater camera system as if he or she were looking around while sitting on the front of the vehicle. Whether the task at hand requires a “flying hand” or a 10,000 ft (3048 m) anthropomorphic diver replacement, the factors to be considered are similar and will be addressed in the following sections.
FIGURE 19.2
Hydro Products RCV 150 using manipulator to support the diver.
19.1 Background 505