Research On The Key Technology Of Manipulator For The Tokamak Toroidal Vessel Maintenance Task

Tokamak is the research device for controlled nuclear fusion technology,which employs a magnetic field to confine the high energy plasma in its toroidal vessel for fusion related experiment.The first wall components of the toroidal vessel are directly exposed to high energy plasma discharge activity during the experiment and may get damaged after several cycles of experiments.This is a severe threat to the research activity and even the safety of the whole tokamak structure.Therefore,to keep the high energy plasma research work continuable and safe,it is necessary to conduct quick inspection of the toroidal vessel first wall completeness during the plasma shut-down intervals without disturbing the inside experiment ambient.Based on the existing in-vessel operation solutions,we proposed an arcuate spreading-arm structure featured manipulator with large toroidal workspace for the Experimental Advanced Superconducting Tokamak(EAST)first wall maintenance task.The manipulator is made up with four main parts,which are the deployment platform,the arcuate spreading big arm,the planar small arm and the end effector.It can be deployed from the tokamak narrow entrance window,can cover the large toroidal vessel workspace and can adapt to the complex geometry constrains of the D-shape section place in toroidal vessel.A manipulator prototype was manufactured and tested in the EAST toroidal vessel mock-up to validate the overall in-vessel operation process.We analyzed the arcuate spreading-arm deformation effect that occurred during the in-vessel operation experiment and cleared out two main causes for the deformation,which were the flexible structure deformation and the spreading-arm joint clearance.A finite element analysis was performed for the structure deformation,an error model analysis was performed for the joint clearance effect,and the combined results were validated through the manipulator prototype deformation test.A compensation method was proposed and validated to fix the vertical direction deformation based on the offline position error data.For the manipulator's high temperature environment compatibility,we analyzed the high temperature influences on the manipulator and the heat transfer situation inside the manipulator.An active circulation cooling method was proposed to keep the key servo drive components in proper working condition.Prototype tests of in-vessel operation procedures under high temperature condition proved the proposal's effectiveness.An overall heat transfer model was established based on the manipulator selected position temperature measurements and the circulation cooling system operating parameters.For the manipulator's overall compatibility to the in-vessel operation environment,the influence principles of three main environment factors,i.e.high vacuum,high temperature and nuclear radiation,were studied separately based on the standard robotic joint actuation pattern.An independent robotic joint module was developed as a study object,which mainly employed a flexible metallic bellow structure to enclose all servo drive structures as protective measures.Environmental tests proved the effectiveness of the protective measures and the viability of the flexible metallic bellow enclosed joint mechanism.