A new underwater manipulator control system comprising a fast PC surface graphics control unit linked to a 68000/VME - bus based subsea arm controller has been developed as part of the ARM (Advanced Robotic Manipulator) project The aim is to produce a new eight degree of freedom manipulator for mounting on an ROV (Remotely Operated Vehicle) to be used for the underwater inspection of offshore structures The first manipulator IS due to be built by SEL in Summer 1993 TSC are producing a PC based system to provide supervisory and robotic control of the manipulator and Incorporating an advanced graphical Interface The manipulator and work piece are presented to the operator as solid shaded Images to provide a 3D impression of the underwater work site A choice of views is available, as well as a view corresponding to an ROV mounted camera, the operator can choose virtual viewpoints at any location around the work piece The manipulator can be controlled by keyboard, mouse, master arm, or other Input devices
In order to limit communications rates over the subsea umbilical and hence Improve reliability and noise immunity several robot control functions are duplicated In the subsea arm control computer An update rate of about 10Hz IS achieved topside which is adequate for graphical presentation and user I/O, whereas the hydraulic manipulator control loop runs at typically 100Hz
The am of the ARM Project is to produce a wholly new kind of sub-sea Inspection system, capable of doing advanced cleaning and inspection tasks in areas beyond the reach of divers It will also be able to work within the domain of divers but at lower cost and with greater safety and reliability In particular, it is a requirement to be able to clean and Inspect complex node welds on sub-sea structures, these nodes generally consisting of a number of intersecting tubular and the welds therefore being of a very complex shape Because of the difficulties of accessing these welds, a completely new system had to be designed from the ground up' Under the sponsorship of Mobil and OSO, a cleaning and inspection system was planned which would Incorporate a completely new underwater manipulator - to be designed, built and tested by Slingsby Engineering Limited (SEL) - and an advanced computer control system, the first of its soon to be designed, built and programmed by Technical Software Consultants Limited (TSC) This paper will describe the Arm Control System software, currently being written by TSC This software IS largely resident In a Topside Computer that provides the interface to the system operator High level commands generated by the Topside Computer are passed down an umbilical link to the remaining part of the system, the Sub-sea Slave Processor This Processor is on the ROV and has closed loop control of the manipulator arm The software In this Processor Interprets commands passed down the umbilical, generates low level movement demands for controlling the manipulator arm, and monitors the arm as it carries out moves
