38 



All ROVs have at least one control for maneuvering the vehicle, some require 

 two. Piloting is made easier on many vehicles by including automatic depth 

 and heading control, where this is the case the controls usually have manual 

 override. Several manufacturers offer portable vehicle control units which 

 allow the pilot to directly observe the vehicle as it maneuvers on the surface 

 in close proximity with the support vessel. 



Control of the manipulators is generally accomplished by manipulation of 

 toggle switches or buttons. The most sophisticated manipulation control 

 is found in Saab-Scania' s ORCA where a link between the control console and 

 slave arm on the submersible gives the operator the feel and impression of 

 actually doing the work in situ. Movement of the master arm is copied by 

 the slave arm. Force and position feedback from the slave manipulator to 

 the master is geared at a force ratio of 13:1. The sense of presence is 

 enhanced by a pan and tilt 200m television camera which is in the same relative 

 position to the work manipulator as the human eye. 



2.1.10 Emergency Location Devices 



There have been several instances in which an ROV has been released (inten- 

 tionally) from its umbilical and either floated to the surface or remained 

 fouled in a structure. By design, ROVs have no more than 5 to 10cm (2 to 4 in.) 

 of surface freeboard, and visually locating them when they surface can be 

 difficult, and sometimes impossible. 



To assist in surface location a self-powered, flashing (strobe) light is 

 affixed to most vehicles which can be intentionally activated by the pilot 

 to assist in nighttime location for maneuvering or is automatically activated 

 if the umbilical is severed. 



Sub-surface location is assisted by an emergency, self-powered pinger which 

 permits homing to the vehicle. Two operators (ULS Marine Ltd. , and Sonarmarine 

 Ltd.) have designed releaseable buoys which, when released, float to the 

 surface and mark the vehicle'^s location. ULS Marine's buoy consists of a 

 standard 9kg (15 lb) plastic float attached to the vehicle by 610m (2,000 ft) 

 of line with a lift capacity of 907kg (2,000 lbs). 



In spite of such precautions several ROVs have been lost simply by floating 

 to the surface and drifting out of visual and/or sonic contact. 



2. 1. 11 Support Vessels 



Remotely operated vehicles have worked and are working from a wide variety 

 of surface support platforms: conventional displacement hull vessels, barges, 

 fixed platforms, semi- submerged vessels, manned submersibles and ice caps. 

 In one instance a vehicle worked off the back of a truck as it examined a 

 flooded mine shaft. The wide range of vehicle dimensions and complexity 

 permits deployment from virtually any floating, fixed, stable or unstable 

 platform. The thrust of this discussion, however, is the requirements for 

 vehicles working in the open ocean. 



