Research On Compliance Control System Of Remote Handling Robot For Graphite Tile Of EAST PFC

The remote handling maintenance system is an essential subsystem for the current tokamak fusion machine because of the strong radiation in the core environment of the tokamak fusion reactor.The maintenance tasks cannot be directly performed by human operations.For EAST tokamak device,due to the huge and complex thermal load,electromagnetic load,it may causes some problems to the internal parts on the first wall surface such as morphology changes,cracks or structural damage,and other failures.As the acquisition of high-quality plasma,the plasma discharge may not be carried out,any failures will affect the safety of the device.To ensure the high-parameter plasma discharge required for the first wall condition,the damage parts must be replaced on due time.The EAMA(EAST Articulated Maintenance Arm)robot,which meets the maintenance requirements of the EAST device,is designed and developed based on the CEA-AIA robot arm.The developed robot cannot only be used to achieve the task of observation by accessing into the vacuum chamber during the discharge gap(High vacuum 10-5Pa,High temperature 80℃),but also,more importantly,to complete the replacement operation for the broken graphite tiles on the first wall.Based on the structural characteristics of the EAMA robot and the structure of the graphite tile,this paper puts forward some suggestions on the compliance control for fixing the bolt of the graphite tiles.The flexible control system of the robot for the replacement of the first wall of the EAST,the design of the actuators,the redundant motion control,the combination of visual and force feedback control methods have been studied.The research topics are from the International Thermonuclear Experimental Reactor(ITER)program "EAST internal components real-time detection,analysis and rapid replacement of key technologies"(No.2014GB101000),the main researches are as follows:1.Investigated and analyzed the current situation and the latest development of the key technology of remote handling maintenance system at home and abroad.Based on the functional requirements and design constraints of the EAST remote handling maintenance system,the EAMA-based remote handling robot system of EAST is proposed.Based on the further research and analysis of the research status of robot compliant control technology,and considering the structural flexibility of EAMA manipulator,a hybrid compliant control system based on visual and force feedback is proposed,and the structure design and redundancy motion control technology and other key technologies are briefly introduced.2.Studied and designed the EAMA robot based on the CEA-AIA robot of France.The modular design is applied to the EAMA segments,the modules include the U-shaped clevis type connecter,the wheel-based yaw driver,the parallelogram-based pitch driver,and the rack and pinion-based shuttle propulsion mechanism.In the aspect of control system,the application of virtual reality simulation technology in remote handling robot distributed control is studied.For the hardware,the CAN-based hardware architecture is studied.3.Developed end-effector for the rapid replacement of graphite tile by utilizing following techniques:using crank shaft and bellow for the rotary sealing of the modular joint,using rope-based structure for the two-finger claw,integrating the visual positioning and force feedback function to the end-sensing module.Considering the safety protection problem of the end-sensing module in the baking process,studies on the non-contact active cooling system is carried out,the cooling system control scheme is proposed,and the verification based on thermal analysis are given.Finally,the basic functions of the actuator are verified.4.Studied the basic problems of flexible motion control in the graphite tile replacement flexible control system,including kinematics model,inverse kinematics solution,flexible model construction and manipulator joint servo controller.Based on the equivalent stiffness of the flexible geometry model and experimental joint equivalent stiffness calculation method,the deflection model of EAMA segment is set up to compensate the deflection error of the segment due to their own weight and load caused by the terminal flexible deformation,thus improve the accuracy of kinematic modeling of manipulator in the virtual simulation environment.In addition,the joint position control system based on three closed-loop controllers is studied,and the design scheme of servo control system is verified by experiment.5.In this paper,we study the necessary hardware configuration of visual and force feedback system,and then study some key technologies in monocular vision positioning,including image feature extraction,camera calibration,camera-robot calibration,pose estimation and other theoretical and technical knowledge.Aiming at the key problem of "plug-in hole" involved in the process of graphite tile disassembly,a dynamic feedback motion control technique based on dynamic motion primitive theory is proposed.In this paper,a method of position uncertainty search based on force feedback is proposed.6.Used UR5 robot as the main body of the demolition of the experimental platform to verify the compliant control system through the experiment on the graphite tile replacement.The results show that the compliant control system has good force feedback control ability,which can adjust the feedback force in real time according to the assembly force,and can reduce the insertion and removal time by the motion learning.And by using the uncertainty location search strategy the affection of errors from the position estimation can be limited to enhance the success of the operation;meanwhile the operation time is extended within the scope of the extended operation.