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The structure design of divertor Multi-Functional Maintenance Platform (MFMP) actuated by hydraulic system for China Fusion Engineering Test Reactor (CFETR) was introduced in this paper. The model of MFMP was established according to maintenance requirements. In this paper, Newton-Euler method and the improved virtual work principle were used, the equivalent driving force of each actuator was obtained through the equivalent Jacobian inverse matrix derived from velocity relationship among the components. The accuracy of the model was verified by ADAMS simulation. The stability control of the heavy-duty components driven by hydraulic cylinders based on Newton-Euler method and improved virtual work principle was established.

A China Fusion Engineering Testing Reactor (CFETR) will be built to test and verify the feasibility of engineering and technology in practice for the future fusion reactor. Long pulse and steady-state operation will be demonstrated with duty cycle time more than 30%–50%. Because of the beta and gamma activation of the component bulk and surface dust (beryllium, carbon, and tungsten), special remote handling (RH) techniques will be required during machine maintenance periods. The divertor cassettes’ remote replacement is one of the key maintenance operations for the CFETR to meet the requirements of duty cycle time. RH maintenance strategies will have a significant impact on the layout of the machine and design of components. In this article, an overview of the CFETR divertor components’ remote maintenance strategy and the description of the maintenance process of the divertor cassettes were introduced. The engineering design features of the divertor RH systems (DHRSs) were described to meet the requirements such as high efficiency and reliability. Preliminary assessment of the divertor RH system is done in order to successfully and efficiently carry out RH maintenance tasks.

The design work of China Fusion Engineering Test Reactor (CFETR) has been started since 2012. In past years, the physical parameters and related engineering design of subsystems were modified, evaluated and redesigned for several rounds in order to fulfill the final scientific goals. Remote maintenance (RM) is identified as one of the key issues of the CFETR because of the neutron activation of the in-vessel components. Different schemes were proposed and comparatively assessed to reach the best possible tradeoff between RM strategies and Tokamak machine designs. This paper will give an overall introduction of the latest version of RM strategy and system conceptual design based on current physical configuration with 16 toroidal field coils and larger sizes. In general, modular blanket components will be removed through only two large vertical maintenance ports while two lower horizontal ports are employed for divertor removing. The work has also provided guidelines for compatibility consideration such as the blanket and divertor modularity, the cryostat pipe arrangement, and the corridor layout to hot cell. In addition, some innovative RM system design for the blanket and divertor maintenance was also provided in the paper, such as the implementation of a toroidal mover transferring blankets to vertical ports, and the novel cask design ensuring storing six divertor at the same time.

Continuum robots with redundant degrees of freedom and postactuated devices are suitable for application in aerospace, nuclear facilities, and other narrow and multiobstacle special environments. The development of a snake-inspired continuum robot is presented in this study. The morphological skeleton structure of the snake body is simulated using underactuated continuum joints, which include several rigid-body joints in series. Each rigid-body joint is driven by the traction of a wire rope. Based on the layered-drive principle, angular synchronous motion can be realized in space with multiple rigid-body joints in a single continuous joint, which can considerably reduce the complexity of the inverse kinematics solution, terminal drive box, and control system. The static and dynamic characteristics of the snake-inspired robot are obtained through torque balance and an equivalent transformation. Finally, we demonstrate trajectory planning and load capacity testing in two robot prototypes with arm lengths of 1500 and 2300 mm (including two and four continuous joints, respectively). The rationality of the structure and the correctness of the control of the layered-drive snake-inspired robot are verified.

The Multi-Purpose Overload Robot (CMOR) is a key subsystem of China Fusion Engineering Test Reactor (CFETR) remote handling system. Due to the long cantilever and large loads of the CMOR, it has a large rigid-flexible coupling deformation that results in a poor position accuracy of the end-effector. In this study, based on the Levenberg-Marquardt algorithm, the spatial grid, and the linearized variable load principle, a variable parameter compensation model was designed to identify the parameters of the CMOR's kinematics models under different loads and at different poses so as to improve the trajectory tracking accuracy. Finally, through Adams-MATLAB/Simulink, the trajectory tracking accuracy of the CMOR's rigid-flexible coupling model was analyzed, and the end position error exceeded 0.1 m. After the variable parameter compensation model, the average position error of the end-effector became less than 0.02 m, which provides a reference for CMOR error compensation.

Purpose This paper aims to present a study on composite coating films for solid lubrication applied on the surface of bearings and gears, which are exposed to the vacuum vessel of a tokamak fusion experimental device running under ultra-high vacuum conditions. Experimental advanced superconducting tokamak is a tokamak fusion experimental device running under ultra-high vacuum conditions. To avoid polluting the inner vessel environment, solid lubrication has been applied on the surface of bearings and gears, which are exposed to the vacuum. Design/methodology/approach Anti-friction MoS2 coatings integrated with Titanium and Carbon have been developed using the multi-target magnetron sputtering deposition technique. This paper presents the comparative testing of tribological properties for three kinds of MoS2-based coating layers. Findings Based on the test results, MoS2-Ti-C coating films are supposed to be the final selection because of the better performance of friction coefficient and lubrication longevity. Originality/value Finally, the detailed information has been characterized for the hybrid coatings, which can provide some references for applications of solid lubrications under similar conditions of high vacuum and temperature.

A concept of the remote handling (RH) tools to maintain the components of the ITER Vacuum Vessel Pressure Suppression System (VVPSS) is developing. These RH tools are designed to remove and replace the rupture disk assembly and the bleed line valve assembly, to clean the relief lines, and to perform any associated operations to maintain them. The RH tools work together with the Neutral Beam Remote Handling System (NBRHS). The main functions of the RH tools are disconnection and connection of the bolted flanges, keeping the static confinement during the RH operations, limiting the spread of contamination, and vacuum or water jet cleaning of the contamination inside the relief line. The RH interfaces in the components are defined during the design process of the RH tools in collaboration with the VVPSS component designers. An RH sequence study is being carried out to demonstrate the feasibility of the maintenance operations within the constrained NB cell environment, and the capability of the NBRHS.

This paper describes the preliminary design result of the Monorail Crane System (MCS), which is a subsystem of the ITER Neutral Beam Remote Handling System. Since the concept design of the MCS, the design is elaborated further detail considering new maintenance requirements, updated interfaces with the components to be maintained, and the latest configurations in the NB cell. The main design updates are described as follows. First, the railway is changed from the one monorail with two side reaction rails to a dual rail system, which has better load distribution within the crane trolley and the building mountings. Second, additional railway and a switching mechanism are added between the HNB#1 and #2 to access to the VVPSS components, which are newly added in the NB cell. Third, the mounting of the transversal beams supporting the dual rails onto the embedded plates are updated and further elaborated. Forth, the crane trolley is designed to have independent redundant kinematic chains so that it is recoverable from a single point failure. Fifth, series of braking systems such as a service brake, an auxiliary brake, and an emergency brake are integrated in each kinematic chain to cope with normal and accidental loads. Sixth, seismic uncoupling devices are integrated to protect the mechanical components of the crane itself and the building structure. Lastly, detailed cabling design is implemented from the control cubicle to the locations where the subcomponents are located.

Among the eighteen upper ports of the ITER Tokamak, the upper ports #4, #5, #6 and #7 are located in the Neutral Beam (NB) cell. A roughing filter and an upper port plug are located inside each upper port. Vacuum Vessel (VV) in-service inspection and neutron flux monitor ports are located on the balcony area near the third Heating Neutral Beam (HNB). This paper describes the concept design of the Upper Port Remote Handling Equipment (UPRHE) that provides means to maintain the components at the upper ports and the balcony area within the NB cell. The UPRHE can move along the toroidal direction to access the upper ports and can deploy various remote handling (RH) tools into the upper ports to access the components that require maintenance. The UPRHE consists of permanent installations in the NB cell and removable equipment that is transferred from the Hot Cell Facility to the NB cell only when carrying out the maintenance activities. The permanent equipment is the cabling device mounted on wall. The removable equipments are the upper port trolley, manipulator transporter, end-effectors, manipulators, and other RH tools. The concept design and the RH compatibility assessment demonstrate that the proposed UPRHE can perform the identified tasks and is ready to move on to the next design phase.

In the ITER or the future DEMO reactor systems, due to the neutron activation, the remote handling tasks such as inspection, repair and/or maintenance of in-vessel and ex-vessel components must be carried out using a wide variety of special tailored automatic manipulators. These manipulators can be designed as a pure serial articulated arm or a pure parallel mechanism, but for the sophisticated remote handling tasks requiring large workspace and high payload/weight ratio, it would be designed as a hybrid structure combined by these two mechanisms. The complex structure to obtain special remote operation makes the maintenance very time-consuming. To obtain the forward and/or the inverse kinematics of these manipulators, a global optimization method combined by differential evolution (DE) and modified particle swarm optimization (MPSO), here we call it as DEMPSO, is developed to save solution time. The general case studies focus on serial, parallel manipulators and the 10-DOF hybrid redundant serial-parallel robot designed for ITER vacuum vessel remote maintenance. The results would be extrapolated to solve the kinematic problems of the ITER or the future DEMO remote handling manipulators. The proposed optimization algorithm can also be used for the static and/or dynamic parameter identification in robot calibration systems.

The remote inspection and maintenance of the small pieces in vacuum vessel requires certain accuracy to the serial long-reach robot applied in EAST tokamak. The elastic deformations due to gravity and dynamical forces, however, will cause a big trajectory tracking error to the robot end. Therefore, the error prediction and compensation strategy should always be studied in advance to achieve a high required accuracy. This paper presents a mathematical method to estimate the static stiffness of EAST articulated maintenance arm (EAMA) robot. Firstly, the stiffness matrix of the modular parallelogram mechanism of robot is obtained based on the Matrix Structural Analysis (MSA) method. Considering the real constraint conditions of robot arms, the matrix is further simplified to a final version with minimum dimension to improve the computational efficiency. Secondly, the simulation examples have been given to evaluate the accuracy and reliability of the stiffness equations. And finally, the results show that the presented approach has an acceptable prediction error (less than 5%), which can be applied to other similar robotic systems with long-reach complex links.

PurposeThe purpose of this paper is to introduce a development and error modeling of a serial redundant manipulator system applied in nuclear fusion environment. Detailed mechanical design of vacuum-compatible arms and actuators are presented, and manipulator flexibility is studied through experiments and model identification algorithm to evaluate the deformation.Design/methodology/approachFirst, the manipulator is designed to be several modular segments to obtain enough and flexible workspace inside the fusion device with narrow and complex geometries. Joint actuators with “rotation-linear-rotation” chains are developed to provide both huge reduction ratios and vacuum sealing. The redundant manipulator system has 11 degree of freedoms in total with a storage cask system to dock with the device vacuum vessel. In addition, to improve the position accuracy, an error prediction model is built based on the experimental study and back-propagation neural network (BPNN) algorithm.FindingsCurrently, the implementation of the manipulator system has been successfully carried out in both atmosphere and vacuum condition. Excellent performance indicates that the mechanical design is suitable. The validation of BPNN model shows an acceptable prediction accuracy (94∼98 per cent) compared with the real measurement.Originality/valueThis is a special robot system which is practically used in a nuclear fusion device in China. It will allow remote inspection and maintenance of plasma facing components in the vacuum vessel of fusion device without breaking the ultra-high vacuum condition during physical experiments. Its design, mechanism and error prediction strategy have great reference values to the similar robots in vacuum and temperature applications.

EAST multi-purpose maintenance deployer (EMMD) system, being collaboratively developed by ASIPP and CEA-IRFM, is built as upgrades for EAMA. Updated kinematics parameters such as DOF distribution and joint angle for EMMD robot are performed and verified in a simulation platform. A new modular joint has been developed to optimize the yaw joint actuator for easy assembly and flexibility reduction. A 3-DOF gripper with cameras and torque sensor has been designed to provide inspection and dexterous handling of small fragments inside the EAST chamber. A conceptual upgrade for EAMA-CASK has been developed for the purpose of protecting the end-effector's sensors which do not have temperature-resistant qualification. The high temperature and vacuum compatible solutions and validation experiments have been presented in this paper.

The present paper introduces a serial-link robot, named treatment table robot (TTR), which is developed for proton medical equipment and installed on the Rotation Gantry. And the task of TTR is to carry and move patient’s body during treatment, which will keep tumor focus of patient in the center of proton radiation. The TTR plays an important part in the quality improvement of proton medical treatment. Taking the reason into consideration, the TTR has to be designed for easy control and good mechanics property. The forward kinematics and inverse kinematics are studied in the paper. And the dynamic performance of the TTR is investigated by multi-body system simulation using ADAMS software. The study results shows the TTR has excellent kinematic and dynamic performance, so that TTR can satisfy the requirement for proton medical treatment.

Fusion Tokamaks are complex machines which require special conditions for their operation, in particular, high vacuum inside the vessel and high temperature of the vessel walls. During plasma phases, the first wall components are highly stressed and a control is necessary in case of doubt about their condition. To be able to make safely such an inspection in a short period of time is a great advantage. The Articulated Inspection Arm (AIA) developed by the CEA provides the capability for fast inspections of the first wall overall surface keeping the vacuum and temperature conditions of the vessel. The robot prototype was validated in Tore Supra in 2008. In the frame of a joint laboratory, CEA/IRFM and ASIPP have decided to upgrade the existing AIA prototype to use it routinely in the EAST and WEST tokamaks. The robot has followed an important upgrade program in 2013 and 2014. The document presents the various upgrades made on the mechanics, the sensors, the electronics, the control station and the integration adaptation for the operation on EAST. From the AIA experience, thoughts for future inspection robots are given.

EAST articulated maintenance arm (EAMA) system is being collaboratively developed by ASIPP and CEA-IRFM for the purpose of remote inspection and simple maintenance operations in EAST vacuum vessel during physical experiments without breaking the ultra-high vacuum condition. The EAMA system design is based on a similar articulated inspection arm robot successfully demonstrated in Tore Supra in 2008. In order to better meet EAST configurations and maintenance requirements, optimized mechanisms and dimensions are considered for EAMA robot as upgrades. Besides, the segmented arm is equipped with a 3-DOF wrist end effector and gripper for gripping operation as well as inspection. Some calculations and simulations on statics, kinematics and workspace of EAMA have been presented to validate the feasibility. This paper introduces the overall design of the EAMA robot and presents implementation progress.

In this study, a single-pump closed-loop hydraulic system with multiple actuators and load sensitivity is designed for a circular transfer platform, which remotely handles the divertor of the China Fusion Engineering Test Reactor by rotating the divertor module in the non-maintenance window to the designated position along the circular track. The proposed system controls the position and force of the pushing and locking cylinders. The designed closed-loop system synchronizes the movements of the internal and external cylinders. It also controls the displacement and force of the locking cylinder, ensuring the stability of the clamping force and the controllable position of the cylinder. Furthermore, the dynamic performance of the hydraulic control system is verified via the Adams–AMESim software co-simulation.

Fast inspection and light maintenance capability is already a clear demand to control the tokamak condition and improve the efficiency of the experimental campaigns. EAST remote maintenance system has been developed to implement inspection and grasping tasks during plasma. The paper presents design description of EAMA (EAST articulated maintenance arm) robot, the gripper and the CASK. The field commissioning was performed both in mockup and EAST tokamak to demonstrate the availability and functionalities of EAMA system. To be able to realize fully routine operation on EAST, improvement of EAMA control system was proposed with integration developed algorithm, such as the robot flexible model modeling, vision servo, motion planning, etc. Finally, thoughts for CFETR In-Vessel Inspection System (CIVIS) are given.

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 (~ 10−5Pa). 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.

EAST Articulated Inspection Arm (AIA) robot is being mutually developed by ASIPP and CEA-IRFM for remote handling maintenance. It will permit remote visual inspection and to pick up small fragments inside the EAST tokamak vacuum vessel during experiments. Considering storage and support for EAST AIA, a sealed cask system has been designed and manufactured, which can be connected to EAST device through a ϕ250 mm connection port with two flashboard valves. The system consists of a 10 m long vacuum vessel with a linear guide rail for storage, guiding and conditioning, two mobile wagons for support and some auxiliary systems for keeping suitable work conditions and measurement. Besides, a stainless steel shuttle has been developed to support AIA robot and assemble with the linear guide. It can push the robot into tokamak vessel and back to the storage cask with a gear-rack driving mechanism. This paper mainly presents the overall description of the system design and some obtained implementation progress.

Tokamak In-Vessel Orbiting robot is mainly used for carrying working robot, which carries out maintenance operations in vessel. With the forward and inverse kinematic algorithms, the continuous path trajectory planning methods are used according to different posture of the robot. The relational curves of these joints angular displacement, angular velocity and angular acceleration are educed by this method. With these movement curves of the joint and the relative position between the circular orbit and the orbit extending robot, we have gotten the movement curves of the three kinematic units belonged to the orbit extending robot, which is smooth and continuous.

KTX is a new reversed field pinch (RFP) magnetic confinement device which is under design in ASIPP and USTC. Major disruption (MD) events may occur in future operating process, which is simulated with the finite element (FE) method. The results present that the peaks of eddy currents on vessel and conductor shell are respectively 11.791 kA and 68.637 kA with maximum stress 67.1 MPa due to high transient electromagnetic (EM) force. It is confirmed that the structure is still strong enough to bear the electromagnetic loads even if the worst case. Besides, as KTX vacuum vessel will take the method of natural cooling for heat dissipation during plasma discharge (0.5–1.0 MA), a preliminary thermal calculation was implemented in normal condition to decide suitable time parameters such as duration and interval. It is suggested that the discharge interval should be no less than 5 min for the complete 1 MA plasma with 100 ms duration, which can guarantee the temperature of vacuum vessel below 200 °C.

KTX (Keda Torus eXperoment) is a new reversed field pinch magnetic confinement device which is designed in University of Science and Technology of China. Its main parameter is between RFX and MST. The vacuum vessel system of KTX is designed to keep plasma in a high vacuum and guarantee the enough mechanical strength to resist stress loads in different working conditions. The main design work has been already completed while the R&D work and preparation for manufacturing and assembling is going on. With the purpose of getting a prediction of the mechanical behavior of KTX vacuum vessel and its supports, electromagnetic and structural finite element models from three different considerations are built. This article presents the calculation methods of mechanical behavior respectively due to the electromagnetic force during plasma disruption, the buckling of elongated support legs and vacuum vessel separating. Furthermore, in accordance with the results, a comprehensive cognition to the relationship between mechanical structure and strength is indicated, so as to complete the detailed and optimization design.