Page 514 - The ROV Manual - A User Guide for Remotely Operated Vehicles 2nd edition

the tooling interface, care should be given to the kinematic function of the tool/receptacle motion. The translational movement aligns the axis of rotation or movement of the end effector (Figure 19.9) while the axis of rotation must align with the tool receptacle in order to assure ade- quate functionality. As discussed later in this chapter, the vehicle stability with reference to the interface is quite important so as to allow seamless kinematic functioning between the end effector and the interface. Standards have evolved within the industry to establish vehicle stability while intervening with subsea valves and/or tooling, thus allowing for smooth operation of subsea systems.
19.1.2.5 Actuator
The mechanism that translates the mechanical force into motion is the actuator. For the hydraulic (or pneumatic) system(s), the pump/cylinder combination transfers fluid motion to linear or rotary motion while the electric actuator performs a similar function using an electric motor as the drive mechanism. Actuators transfer work to the manipulator in order to overcome the various forces opposing the system’s movement along with configuring the geometry of the end effector for per- forming the work. In Figure 19.10(a), cylinder linear motion is either transferred to rotary (or lin- ear) motion (for moving links) in a limited range while the gerotor actuator (Figure 19.10b) performs continuous rotation for rotating the wrist attached to the end effector.
19.1.2.6 Manipulator/wrist/end effector combination
The system becomes a manipulator when the series of links, joints, and structure combine with the wrist/end effector for performing work. The joint between the last link (forearm) and the end effec- tor is the most important as it controls the final orientation of the end effector. It is thus termed the “wrist.” The term “positioning” refers to placing the end effector to a point within the geometric workspace while “orienting” refers to moving it to its proper orientation once at that point. End effector positioning is for the arm, and orienting is for the wrist.
θ3
19.1 Background 511
θ2 θ1
bolt
FIGURE 19.9
Translational moment versus rotational moment.
Translational
Axis of rotation
Rotational