in water in a real-time control mode with a good video picture from an under- 

 water television camera mounted to the vehicle with a small, twisted-pair 

 tether. Thus, since the fiber-optic subsystems have been fabricated and 

 individually tested, all that remains is to install and test the various 

 components on the submersible. 



Navigation Subsystem 



Three basic navigation methods have been designed for the EAVE WEST sub- 

 mersible: preprogrammed trajectory and magnetic pipe following when operating 

 under the autonomous mode and visual orientation when operating under the pro- 

 jection mode. 



The vehicle's preprogrammed trajectories are presently executed through a 

 dead-reckoning navigation sensor, i.e., a magnetic compass, a depth sensor, 

 and an internal timer are used to navigate from one point to another. Such an 

 approach, of course, leads to drift errors because of ocean currents. If, 

 however, an off-the-shelf bottom transponder navigation system were added to 

 the vehicle, software programming of the control equations could be accom- 

 plished in the same general manner used for the existing dead-reckoning ap- 

 proach. Error signals would be generated to compensate for the difference 

 between a desired position and the actual position measured by the navigation 

 system. The cost of such a system could, however, approach the present devel- 

 opment cost of the vehicle. Because of this and also to avoid redeveloping 

 technologies already existing, a simple dead-reckoning approach was installed 

 for demonstration purposes. 



A magnetic-pipe-following system will soon be incorporated in the vehicle 

 to allow autonomous tracking of a pipeline located either on the ocean bottom 

 or buried beneath it. The system uses magnetic induction to autonomously 

 follow a 48-in pipeline at a vertical distance of up to 18 ft. The magnetic 

 sensor and transmitter are separated from each other and the vehicle to limit 

 interference (see figure 3). A block diagram of this approach is shown in 

 figure 15. The system uses two receivers and one transmitter operating at 

 frequencies selectable from 40 Hz to 4 kHz. The basic problem involved is to 

 discriminate the received signals from the transmitting signal with as high a 

 signal-to-noise ratio as is possible. Details of this sensor system will be 

 discussed in a separate report. 



A television camera has been installed on the vehicle to provide a visual 

 means of navigation along a pipeline or within a structure when the vehicle is 

 operated in projection mode. Transmission of the signal to the console opera- 

 tor will be via the fiber-optic link when it is installed and operational. In 

 addition, however, NOSC is pursuing a means of transmitting the video acous- 

 tically to the surface. Display of 128-by-128 and 256-by-256 picture elements 

 has been tested and determined to operate to depths of 4000 ft (reference 

 11). This is another technology subelement being investigated as a part of 

 the free-swimmer technology development program. 



Data Acquisition Subsystem 



A Subsea Systems, Inc., silicone diode array camera with a 600-line 

 resolution capability and a 75-W quartz iodide light is presently installed as 

 one of the major sensors for visual inspection of pipelines and structures. A 



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