Advanced telerobotic controller

Abstract

An advanced telerobotic control system has been developed for a subsea manipulator as part of the ARM (Automated Remote Manipulation) project. This project is being conducted by a consortium comprising Mobil North Sea Ltd (MNSL), the Offshore Supplies Office (OSO), Slingsby Engineering Ltd (SEL), Technical Software Consultants Limited (TSC) and University College London (UCL). The arm controls comprise a fast PC surface graphics control unit linked via the Remotely Operated Vehicle (ROV) umbilical to a 68000, VME-bus based subsea arm controller. This provides supervisory control of the manipulator, including manual master-slave tele-manipulation and fully automated, robotic task execution. A 3D video representation of the ROV, manipulator and work site is presented to the operator using solid shaded colour graphics, and can be used to monitor the arm whilst planning or executing tasks. The viewpoint can be modified to aid visualisation, and secondary windows used to display plan and elevation views of the arm and its work area. Also the arm can be viewed as if from an ROV mounted camera to give a close up which should correlate with actual television images. The arm can be controlled by a choice of input devices including keyboard, mouse, master arm or joysticks and operated in a variety of co-ordinate systems such as joint, world, tool, workpiece, etc. Standard serial communications have been used between the surface and subsea computers to improve readability and noise immunity. This requires a number of software modules to be implemented in both computers; these include inverse kinematics, path generation and collision detection routines. The topside computer has an update rate of 5 Hz which gives adequate sampling of the input device and refresh of the graphics. The subsea computer works at 50 Hz to give high bandwidth arm control. The first prototype arm has been fabricated and tests are in progress with the control software. This paper describes the operation of the arm undergoing a range of typical tasks. The tasks include tactile cylinder sizing and location to determine the trajectory of a nodal weld, and tracking round the weld with an inspection probe.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>