Remote handling dynamical modelling: Assessment of a new approach to enhance positioning accuracy with heavy load manipulation

In-vessel maintenance work in Fusion Tokamak will be carried out by the help of several sets of robotic devices. Handling of heavy loads in constrained space is identified by all players of the RH community as a key-issue in behalf of the ITER. To deal with high-level dexterity tasks, characterized by high payload to mass ratio and limited operating space RH equipment designers propose systems whose mechanical flexibility is no longer negligible and needs to be taken into account in the control scheme. A traditional approach where control system includes a linear model of deformation of the structure only leads to poor positioning accuracy. During maintenance operations in the ITER facility, uncontrolled or under-evaluated errors can damage in-vessel components. To address the control of complex flexible systems, we will investigate the use of specific mechanical software that combines both finite element and kinematical joint analyses with a strong-coupled formulation to perform system dynamics simulations. This approach will be applied to a single axis mock-up of robotic joint, supplied by a highly flexible structure. A comparison of experimental results with the traditional linear approach and the specified software model is carried out.