Verifying elementary ITER maintenance actions with the MS2 benchmark product

A new facility has been taken in operation to investigate the influence of visual and haptic feedback on the performance of remotely executed ITER RH maintenance tasks. A reference set of representative ITER remote handling maintenance tasks was included the master slave manipulator system (MS2) benchmark product. The benchmark product was used in task performance tests in a representative two-handed dexterous manipulation test bed at NRG. In the setup, the quality of visual feedback was varied by exchanging direct view with indirect view setups in which visual feedback is provided via video cameras. Interaction forces were measured via an integrated force sensor. The impact of feedback quality on the performance of maintenance tasks at the level of handling individual parts was measured and analysed. Remote execution of the maintenance actions took roughly 3-5 times more time than hands-on. Visual feedback was identified as the dominant factor, including aspects like (lack of) operator control over camera placement, pan, tilt and zoom, lack of 3D perception, image quality, and latency. Haptic feedback was found to be important, but only in specific contact transition and constrained motion tasks. (C) 2011 Elsevier B.V. All rights reserved

Analysis and validation center for ITER RH maintenance scenarios in a virtual environment

A facility for detailed simulation of maintenance processes in the ITER Hot Cell Facility (HCF) has been taken into operation. The facility mimics the Remote Handling (RH) work-cells as are presently foreseen. Novel virtual reality (VR) technology, extended with a physics engine is used to create a realistic setting in which a team of Remote Handling (RH) operators can interact with a virtual Hot Cell environment. The physics engine is used to emulate the Hot Cell behavior and to provide tactile feed-back of the (virtual) slave. Multi-operator maintenance scenarios can be developed and tested in virtual reality. Complex interactions between the RH operators and the HCF control system software will be tested. Task performance will be quantified and operational resource consumption will be estimated. (C) 2011 Elsevier B.V. All rights reserved

Introducing artificial depth cues to improve task performance in ITER maintenance actions

Maintenance operations on ITER tokamak components will be largely performed by remote handling. In previous work it was shown that representative maintenance tasks could be performed significantly faster with direct visual feedback than with camera feedback. In post-test interviews, operators indicated that they regarded the lack of 3D perception as the primary factor hindering their performance. This paper discusses various techniques to improve depth perception in teleoperation, including stereo vision, head tracking, virtual camera views and depth gauges. The most promising techniques were tested. Performance metrics included time-to-complete, path analysis and operator work-load. In a first experiment, artificial depth gauges views were tested in a 1:1 scale hardware testbed with mechanical master-slave manipulators handled by experienced operators. Robust real-time image processing was achieved with marker-based objects. The simple depth gauge and graphical overlay did not significantly improve task performance. Operators commented on their view of the task being “obstructed” by the graphical overlay, and the depth gauge was judged not very informative. In a second experiment, real time tracking was combined with VR display including stereo and head tracking. While stereo was found to improve the task performance significantly over the 1 camera (mono) condition, head tracking unexpectedly did not

Influence of visual feedback on human task performance in ITER remote handling

In ITER, maintenance operations will be largely performed by remote handling (RH). Before ITER can be put into operation, safety regulations and licensing authorities require proof of maintainability for critical components. Part of the proof will come from using standard components and procedures. Additional verification and validation is based on simulation and hardware tests in 1:1 scale mockups. The Master Slave manipulator system (MS2) Benchmark Product was designed to implement a reference set of maintenance tasks representative for ITER remote handling. Experiments were performed with two versions of the Benchmark Product. In both experiments, the quality of visual feedback varied by exchanging direct view with indirect view (using video cameras) in order to measure and analyze its impact on human task performance. The first experiment showed that both experienced and novice RH operators perform a simple task significantly better with direct visual feedback than with camera feedback. A more complex task showed a large variation in results and could not be completed by many novice operators. Experienced operators commented on both the mechanical design and visual feedback. In a second experiment, a more elaborate task was tested on an improved Benchmark product. Again, the task was performed significantly faster with direct visual feedback than with camera feedback. In post-test interviews, operators indicated that they regarded the lack of 3D perception as the primary factor hindering their performance

Analysis of ITER upper port plug remote handling maintenance scenarios

The ITER tokamak has a modular design, with port plugs, blanket modules and divertor cassettes. This set-up allows for maintenance of diagnostics, heating systems and first wall elements. The maintenance can be done in situ, or in the Hot Cell. Safe and effective remote handling (RH) will be ensured by the RH requirements and standards. Compliance is verified through remote handling compatibility assessments at the ITER Design Review milestones. The Remote Handling Study Centre at FOM Institute DIFFER is created to study ITER RH maintenance processes at different levels of complexity, from relatively simple situational awareness checks using snap-shots in the CAD system, time studies using virtual reality (VR) animations, to extensive operational sequence validation with multiple operators in real-time. The multi-operator facility mimics an RH work-cell as presently foreseen in the ITER RH control room. Novel VR technology is used to create a realistic setting in which a team of RH operators can interact with virtual ITER environments. A physics engine is used to emulate real-time contact interaction as to provide realistic haptic feed-back. Complex interactions between the RH operators and the control room system software are tested. RH task performance is quantified and operational resource usage estimated. The article provides a description and lessons learned from a recent study on replacement of the Steering Mirror Assembly on the ECRH (Electron Cyclotron Resonance Heating) Upper Launcher port plug

Applying HAZOP analysis in assessing remote handling compatibility of ITER port plugs

This paper describes the application of a Hazard and Operability Analysis (HAZOP) methodology in assessing the criticality of remote handling maintenance activities on port plugs in the ITER Hot Cell facility. As part of the ECHUL consortium, the remote handling team at the DIFFER Institute is developing maintenance tools and procedures for critical components of the ECH Upper launcher (UL). Based on NRG's experience with nuclear risk analysis and Hot Cell procedures, early versions of these tool concepts and maintenance procedures were subjected to a HAZOP analysis. The analysis identified several weak points in the general upper port plug maintenance concept and led to clear recommendations on redesigns in port plug design, the operational sequence and ITER Hot Cell equipment. The paper describes the HAZOP methodology and illustrates its application with specific procedures: the Steering Mirror Assembly (SMA) replacement and the exchange of the Mid Shield Optics (MSO) in the ECH UPL. A selection of recommended changes to the launcher design associated with the accessibility, maintainability and manageability of replaceable components are presented

The ITER EC H&CD Upper Launcher: Maintenance concepts

Maintenance of the ITER EC H&CD Upper Launcher (UL) shall be performed through the use of Remote Handling (RH) in the ITER Hot Cell Facility (HCF). The UL design will have to be fully compliant with ITER RH maintenance requirements and the set of RH tooling and services available in the HCF. This paper describes the development of an overall maintenance strategy for the UL, starting from a listing of all conceivable maintenance operations, including hands-on tasks. Components for which design concepts are discussed in this paper are the Blanket Shield Module (BSM), the steering mirror (M4), the mid optics (M1, M2) and the waveguide (WG) feed-through plate. Aspects related to RH documentation, overall maintenance strategy and design concepts for optimizing the maintainability of the UL are presented

The ITER EC H&CD upper launcher: Analysis of remote handling compatibility

The present design of the ECH (Electron Cyclotron Heating) upper port launcher has been evaluated in light of the ITER remote handling (RH) requirements. Changes to the launcher design associated with the accessibility, maintainability and manageability of replaceable components are presented. Captive bolts were placed along the flange of the Blanket Shielding Module (BSM). A hinge mechanism was integrated to simplify the (dis-)mounting of the BSM and a frame with incorporated cooling and actuation lines was suggested for simplified mounting and replacement of the steerable mirrors. Rotating the upper port plug upside-down improves maintenance access and component handling. Tools are proposed for manipulation of the port plug and its sub-components. The RH compatibility analysis can improve a design. Early consideration of RH requirements and implementation of necessary features is therefore vital. (C) 2011 Elsevier B.V. All rights reserved