Page 516 - The ROV Manual - A User Guide for Remotely Operated Vehicles 2nd edition
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  FIGURE 19.11
Parallel and intermeshing manipulator jaws. (a) 6-inch parallel jaw and (b) 11- and 7-inch intermeshing jaws.
(Courtesy Schilling Robotics.)
The large work-class manipulators are not the only ones with interchangeable hands. SeaBotix’s grabber (Figure 19.12), as used on their small ROVs, not only incorporates parallel or interlocking jaws but also can be outfitted with a line cutter.
19.1.2.8 Manipulator control
As further discussed below, the two variables for arm actuation are force and slew rate. The sim- plest form for movement of a hydraulic arm (Figure 19.13) would be adjusting the system’s pres- sure and flow (and pressure relief) upon the arm’s actuator to either slew the arm quickly or slowly and then to apply a certain amount of pressure/force before stopping the arm’s movement (and relieving the pressure back to the tank).
For electrical actuation of manipulator systems, the two types of controls are classified as either servo control (closed loop) or non-servo control (open loop). Servo manipulators are mostly used in manufacturing applications for performing redundant tasks, leaving the non-servo control for the subsea vehicle realm (the exception is with use of a position-controlled manipulator system).
The two types of controls of subsea manipulator systems are “rate control” and “position control.” The simplest of these two types is the rate-controlled arm. In rate controller, each joint is singled for actuation in series, thus moving individual joints toward the end goal. In the position controller, the position of the joystick or controller arm is in a truly “masterslave” configuration, whereby the arm mimics the position of the controller. Whereas the rate controller isolates each joint for movement toward the final goal, the position controller moves several joints simultaneously to orient the arm in unison with the controller. Typically, while the position controller is more elegant, the rate controller is more robust as the position controller requires calibration periodically.
19.1 Background 513
  

























































































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