Development of a virtual reality simulator for the ITER blanket remote handling system
Introduction
Maintenance activities in the ITER must be performed remotely, because the 14-MeV neutrons resulting from fusion reactions induce the activation of structural material and gamma ray emission. Avoiding collisions between the remote maintenance system and in-vessel components is generally one of the most critical issues. Therefore, visual information about the vacuum vessel is needed to understand the relative positions of devices and components with high precision. However, the arrangement of viewing cameras in the vessel is limited because of restricted space and high gamma ray intensity. It is therefore likely that the number of cameras and lights will be insufficient. Furthermore, the visibility of areas of interest, such as positions where two components come into contact during installation, is frequently interrupted by other devices and components. Thus, it is difficult to determine the relative positions of devices and components using only visual information even if adequate number of cameras and lights are provided. For these reasons, a simulator that can recognize the position of each device and component is indispensable for remote handling systems in fusion reactors.
In the JET, a real-time simulator with 3D computer graphic models for preparation and support of remote handling operations has been in use since the mid-1980s [1]. A simulation system for remote handling is also planned for the ITER [2], and a computer simulation system for the divertor remote maintenance system was developed at the Divertor Test Platform (DTP) at ENEA Brasimone [3] during the Engineering Design Activity (EDA).
This paper introduces a 3D real-time simulation system for the ITER blanket remote maintenance equipment. This system was applied to the ITER blanket maintenance manipulator, which was constructed during the EDA [4]. Knowledge obtained through operation of the system will be reflected in the final specifications of the real system, which will be procured by Japan and delivered to the ITER Organization.
Section snippets
Blanket maintenance manipulator
During the EDA, a full-scale blanket maintenance system, including a 180° rail, was fabricated to demonstrate its feasibility in the framework of the ITER Seven Large R&D Projects. As shown in Fig. 1, the system was integrated into the Blanket Test Platform (BTP) at the Tokai site of the Japan Atomic Energy Research Institute (JAERI, later merged with the Japan Atomic Energy Agency) [4]. In the BTP, a sensor-based control test [5] and rail deployment test [6] were performed successfully.
Simulator requirements
According to the Design Description Document, the following features are required for the remote handling equipment simulator [2]:
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On-line visualization:
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Real-time viewing during actual operation.
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Off-line simulation:
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Testing a taught sequence.
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Operator training.
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To enable real-time viewing, the simulator should implement a network interface function to receive position data for the joints from the control system through a LAN. For this purpose, the 3D robotic simulation software TeleGRIP from Deneb
3D model
A 3D model was developed in CATIA using 2D drawings of the manipulator. All of the joints were simulated except for two locking wedges. One of the modules was also modeled for testing a taught sequence.
Network connection
As shown in Fig. 3, the control systems for the manipulator and the simulator are connected by a LAN. A gamepad used for manual input is also connected to the LAN through a PC. The simulator and the gamepad PC used the Windows operating system, while the control system used VxWorks on a VME CPU
Conclusion
A simulator for the remote maintenance system of the ITER blanket was developed using general 3D robotic simulation software. The simulator was connected to the control system of the manipulator, which was developed as part of the blanket maintenance system during the EDA, and was able to reconstruct the positions of the manipulator and blanket module using position data transmitted from the motors through a LAN. In addition, it can provide virtual visual information (e.g., showing connecting
Acknowledgments
The authors acknowledge the valuable contributions of Toshiba Corp. in fabricating the manipulator and the original control system, of Mr. T. Shimada in producing the 3D CAD model of the manipulator, and of Mr. H. Henmi in developing the network communication software for the simulator. The authors also express their sincere gratitude to Drs. R. Yoshino and T. Tsunematsu for their continual suggestions and encouragement during these activities.
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