Development and Error Compensation of a Flexible Multi-Joint Manipulator Applied in Nuclear Fusion Environment

Abstract

Experimental Advanced Superconducting Tokamak (EAST) is the world's first fully superconducting tokamak fusion device with non-circular cross-section which was built in China The EAST articulated maintenance arm (EAMA) system is developed for real-time detection and rapid repair operations to damaged internal components during plasma discharges without breaking the EAST ultra-high vacuum (UHV) condition. To achieve the desired objectives, the EAMA system design should guarantee that the robot can stably run in the harsh environments of high temperature (80-120 °C) and high vacuum (~ 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-5</sup> Pa). Meanwhile, the errors caused by the deformation of long flexible robot arms should also be predicted and compensated in real-time to obtain high accuracy for maintenance operations. In this paper, the vacuum-available design scheme of the manipulator system was firstly introduced. Secondly, inverse kinematics and obstacle avoidance strategy of the highly redundant EAMA robot was built. Then, flexible errors were predicted utilizing a back-propagation neural network (BPNN) model which was established on the basis of real experimental data. Finally, an integrated control strategy for error prediction and compensation was developed.