Page 515 - The ROV Manual - A User Guide for Remotely Operated Vehicles 2nd edition

512 CHAPTER 19 Manipulators
Pump Tank
(a) Base
FIGURE 19.10
Oil out
Oil in
(b)
Hydraulic actuation for both (a) cylinder (limited rotation) and (b) gerotor (continuous rotation).
19.1.2.7 End effector
The free end of the base/joint/link chain contains the end effector. This allows for the final physical interface between the vehicle and the environment. The base/joint/link combination is present to simply maneuver the end effector into a suitable position to accomplish the work.
The simplest end effector is the gripper. It is capable of opening and closing for gripping objects. That grip can be used as a contact point for steadying the vehicle or it can be used to grip and maneuver a tool (which then becomes part of the end effector).
In standard robotics, the end effector can be any of a number of mechanical devices including a torch, grabber, grinder, electromagnet, brush, torque tool or any other mechanical device. However, in the subsea industry, end effectors other than a hand/jaw/gripper are typically classified under “tooling” as opposed to “manipulator.” To correlate to anthropomorphic terms, a human would grab a wrench (spanner) from a tool chest to turn a bolt—the actual end effector is the wrench (spanner)/hand combination with the hand being a part of the end effector.
End effectors are, by convention, the working end of the manipulator, that is, the hand. But the design of the hand is highly dependent on what the required tasks are. Most manipu- lators have various hands that can be installed on the manipulator prior to launch of the vehi- cle. The hands are designed for a range of tasks, to include interfacing with and operating various tools. The various hand types and types of tooling are discussed below and in the next chapter. The manipulator or grabber hands (or jaws) are generally made up of two to four fingers/tines that operate in a parallel fashion or intermesh to grasp an object or tool. Examples of the parallel and intermeshing jaws are shown in Figure 19.11. Such grippers are well suited to grasp objects by closing the fingers around the structure or tool. Further, these parallel and intermesh hands are typically ISO 13628-8/API 17H compliant and mate readily with standardized tooling handles and wellhead interfaces. Most hydraulic manipulator jaws operate in the “fail-to-open” mode so that, should a hydraulic malfunction occur while the grabber is locked onto a platform, the manipulator will release the structure so the vehicle may be recovered and repaired.
Housing