cutting 
head 
work 
(c) flexible system 
(capable of under- 
(a) proposed mode (b) conventional milling cutting itself) 
machine 
Figure 50. Useful movements in a profiling cutter. 
Figure 51. Modified commercially available hydraulic crane suitable for 
automated polar coordinate controls. 
The least conclusive aspect of the entire study and preliminary design 
was control of the Excavator’s cutter head with respect to the ocean’s bottom 
with sufficient accuracy to do useful work. The system recommended in the 
report for further design, fabrication, and testing would utilize three trans- 
ponders in an array extending beyond the work site. These would be 
interrogated by a transducer on the cutter head to permit the position of 
the cutter to be calculated from the response times by a mini-computer on 
the surface. The system is described not only in Northrop (1970) but ina 
paper by Coxe and Buckley (1970). 
63 
