pressure hulls, and structural components for increasing depth and stringent operating 

 conditions. The aramid fiber kevlar is being applied as a strength member for undersea 

 cabling and as the reinforcing member in plastic composite sheets and structural members. 

 The resulting weight savings is a factor of four to six. To lighten the density of undersea 

 cables, increase the data signal bandwidth and reduce cross-talk and outside electrical and 

 radio-frequency interference; fiber-optic elements are also being applied to the tether cables 

 of undersea vehicles. 



TOOLS 



For most routine undersea operations, two-function claws of various sizes and 

 shapes, cutters, and simple toggle bolts are sufficient for most work tasks. For certain of 

 the more dexterous tasks, multifunction manipulators and specialized tools are necessary. 



MANIPULATORS 



A manipulator must be mechanically well designed for performing the required 

 tasks in the marine environment, and it must be integrated with controls and displays 

 so that the operator can perform coordinated, accurate motions. Anyone with experience 

 in remote work systems develops opinions on how to design a manipulator to optimize the 

 capabilities of the operator through the man-machine interface, but these opinions must be 

 reconciled with the experience of others, i.e., the human factor researchers and the 

 operators. 



The optimum manipulator and control system varies with the task. The capabilities 

 of operators also vary, and their preferences are often a function of their experience with 

 particular types of manipulators, controls, displays, and tasks. However, experience has led 

 to a general awareness of certain tradeoffs. For example: for tasks requiring precise 

 positioning, rate-control devices are more accurate; whereas for general reaching and grasp- 

 ing, where coordination is more important than precision, master-slave manipulators are 

 much faster. In rate-control manipulators, position feedback is purely visual; whereas 

 for master-slave manipulators, even with computer-generated displays, there is also a 

 natural feeling of position. Two types of master-slave controls have been used: harness and 

 terminus control. A harness control straps onto, or in some way attaches to, the arm of the 

 operator; the terminus control is held only at the hand or terminus. They operate in the 

 same way: the manipulator (slave) is driven to conform to the configuration and position 

 of the control (master). The harness control may be most valuable for use with anthro- 

 pomorphic manipulators, especially those with a redundant function for elbow position. 

 Terminus control, much more common in hot-cell nuclear work, generally allows more 

 operator freedom and a greater range of motion and does not require an anthropomorphic 

 manipulator. 



15 



