31 



freedom and can perform tasks such as handling tools, providing force and torque, 

 taking samples, placing instruments and clearing debris. The grabber manipulators 

 have six degrees-of- freedom. Either of the grabbers can be used as an anchor 

 while the other performs work tasks or assists the master-slave manipulator 

 during work. In lateral water currents both grabbers may be needed as anchors 

 or thruster supports in order to keep the submersible in a fixed position 

 during work. 



The master-slave manipulator is a bilateral, terminus-control unit with general 

 purpose capability and high accuracy. The system consists of one master arm 

 and an electronic package mounted at the operator console and one slave arm 

 on the submersible and an electronic package in the capsule. The operator 

 grasps the handle of the master, which, except for appearance and detail, is 

 geometrically similar to the slave arm. The master joint axes correspond to 

 those of the slave, and the master members' lengths are scaled proportional 

 to the slave members. The operator moves the master, concentrating on the 

 position and orientation of the slave grip on the monitor. The slave joint 

 axes follow those of the master (position-control) . The terminus- control 

 system allows a greater range of movement in certain of the joints than the 

 operator's own arm does. The operator must therefore ignore lack of spatial 

 correspondence between his own arm and the master in all but the hand position 

 in space. The work effector includes force- feedback to all master functions 

 except grip to achieve positional bilateral (force and position feedback) 

 control modes. 



The slave arm is bolted to the right of the vehicle's x-axis. The arm is 

 mounted on the skeleton frame and connected to the vehicle's hydraulic pack 

 and to the data transmission system. 



The grabber manipulators are located one on each side of the front end of the 

 submersible low to right and high to the left and bolted to the skeleton frame. 

 The necessary valves for controlling the grabber manipulators are installed 

 in an electro-hydraulic control box one for each grabber. These boxes are 

 connected to the grabbers with hoses and at the other end to the data trans- 

 mission system and to the hydraulic pack. One, two or all manipulatives can 

 be carried on a single mission. 



2.1.7.e Echo Sounders 



The echo-sounder provides primary input into vehicle altitude or distance- 

 to- the-bottom. The type and capabilities of echo-sounders vary, some are 

 conventional devices which measure the height of the vehicle from nominally 0.3m 

 (1 ft) to 61m (200 ft) and display this information digitally. A few are 

 scanning or forward-looking sonars which can be tilted vertically downward 

 to serve as an echo-sounder. Sub Sea Surveys Ltd. uses a very high accuracy 

 (750kHz) echo-sounder which not only measures vehicle altitude, but also 

 produces a heave- compensated bottom profile which is used as a trench and/or 

 pipe profiling record. The two major data inputs are the high frequency 

 transducer and a high precision micro processor-based pressure sensor. Data 

 from both sensors are fed to a DEC PDP II computer where they are programmed 

 to remove vehicle motion, plot the pipe trench profile and are stored. By 

 "flying" the vehicle across the pipeline at various intervals. Sub Sea Surveys 

 reports that echo soundings of 1cm (0.4 in.) accuracy are attainable with this 

 system. 



