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Design and testing of the Fusion Virtual Assembly System FVAS 1.0
Fusion Engineering and Design 82 (2007) 2062–2066
Design and testing of the Fusion Virtual Assembly System FVAS 1.0 P. Long ∗ , S. Liu, Y. Wu, the FDS Team Institute of Plasma Physics, Chinese Academy of Sciences, P.O. Box 1126, Hefei, Anhui 230031, China Received 31 July 2006; received in revised form 6 July 2007; accepted 6 July 2007 Available online 20 August 2007
Abstract This paper presents the Fusion Virtual Assembly System FVAS 1.0 which makes possible engineering application for assemblies of large-scale complex nuclear facilities. This system focuses on utilizing a desktop virtual environment tightly coupled with commercial Computer Aided Design (CAD) systems, and is designed to support assembly planning, evaluation, demonstration, and training, and to work on personal computer (PC) platform. Main features of FVAS include: (1) automatic assembly modeling, (2) separation of display scene and collision detection scene, (3) multi-way assembly planning, (4) records and replays of assembly processes. This paper describes the system architecture, features and capabilities of FVAS. And tests conducted using real-world engineering models are also described. © 2007 Elsevier B.V. All rights reserved. Keywords: Virtual assembly; Collision detection; Virtual roaming; Nuclear facility
1. Introduction Due to the complicated structure and high precision requirements of nuclear machines, detailed accurate assembling procedures must be planned before the practical assembly. However, assembly planning for complex systems has always been a difficult task for engineers. Although CAD systems allow configura∗ Corresponding author. Tel.: +86 551 559 3326; fax: +86 551 559 3326. E-mail address: [email protected] (P. Long).
0920-3796/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.fusengdes.2007.07.010
tion evaluation by letting engineers visualize the final assembly, these systems do not support the visualization or planning of the assembly process. Although many systems (such as the one described by Kaufman et al. [1]) are attempting to automate the planning process, it is very difficult to formalize assembly planners’ knowledge. Thus, physical prototypes are still the primary mode of planning and evaluating assembly processes. The development of applications of virtual reality (VR) in engineering has opened up a powerful array of tools to solve above problems. Virtual assembly
P. Long et al. / Fusion Engineering and Design 82 (2007) 2062–2066
(VA), utilizing VR technologies to plan and evaluate assembly processes, retains the benefits (time-saving, inexpensive, and no hazardous) of VR technologies and conquers the shortcoming of physical prototypes, such as long circle, high cost, low precision. Engineers can perform the assembly intuitively in the virtual environment using VR hardware and software. The Fusion Virtual Assembly System (FVAS) is a VR based engineering application which is designed to support planning, evaluation and demonstration of assembly processes, and assembly training, and to work on PC platform. This system has been implemented successfully and is being evaluated using test cases from real-world engineering. In this paper, we describe the system architecture, features and capabilities, and tests of FVAS.
2. Fusion Virtual Assembly System FVAS has been designed and implemented by the FDS Team using Visual C++ and Open Inventor [2] at ASIPP. The overall system concept is illustrated in Fig. 1. Once the engineer designs the mechanical system using any CAD system (e.g. Unigraphics), FVAS automatically imports the necessary data to the virtual environment through a user selected option. In the virtual environment, the user is presented with an assembly scene. The VR user can import various parts in the preassembly area, and then perform the assembly. This enables the user to explore and vali-
2063
date assembly processes, and perform a host of other engineering tasks in the virtual environment. The FVAS’s architecture is based on object-oriented design concepts and methods. There are seven main modules in the system: (1) ModelConverter: Converts parts’ CAD models into VR assembly models. (2) ViewpointsManager: Manages viewpoints, provides interface to manipulate the active viewpoint and to switch among all viewpoints, and realizes virtual roaming. (3) PartsManager: Manages all parts in the scene, and provides interface to manipulate parts. (4) CollisionManager: Provides real-time collision detection and response, and feeds back information used in the steps that follow to determine object movement. (5) AssPlanManager: Obtains and processes user input of data and commands, manages the human/computer interaction, and realizes assembly simulation. (6) AssReplayManager: Parses assembly script files, updates scene displays, and replays assembly processes. (7) AssemblyManager: Harmonizes all modules and the whole system, records the assembly process to script files. In above modules, PartsManager and CollisionManager are the core sections. AssPlanManager and AssReplayManager serve as the application inter-
Fig. 1. System architecture of FVAS.
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P. Long et al. / Fusion Engineering and Design 82 (2007) 2062–2066
face. The AssemblyManager is a bridge between core sections and application interface. And ModelConverter and ViewpointsManager are assistant modules.
3. Features and capabilities of FVAS (1) Automatic assembly modeling: Polygon-facet models of Mechanical Parts are needed for FVAS’s virtual environment. A CAD conversion utility program was written to translate CAD geometry files to VR assembly model files, which not only contain polygon-facet geometry information, but also include any assembly information used during assembling. (2) Separation of display scene and collision detection scene: To enhance the real-time performance of assembly simulation for large-scale nuclear facilities, a policy based on separation of display scene and collision detection scene has been adopted. The display scene can be predigested to reduce the time of scene refreshment, and the collision detection performance is greatly improved by using the mature interference check ability of commercial CAD systems.Convenient observation mechanism brings more practicability. So a multi-viewpoints roaming scheme has been utilized to facilitate users’ assembly operation in the display scene. Users can obtain much optical information from multiple angles by manipulating viewpoints.According to the Collision Detection Concept Based on VR-CAD [3], an improved VR-CAD based collision detection (CD) method is utilized to enhance the CD efficiency. With this method, the check number is reduced from (n − 1)n/2 to (n − 1) for a collision detection scene of n parts during one checking. (3) Multi-way assembly planning: Three assembly planning modes are supported in this system: (a) interactive virtual assembly, (b) assembly path planning, (c) automatic path planning. During interactive assembly, users can realistically manipulate virtual tools to perform assembly operations. An assembly path could be specified through the path-planning interface, and then the assembly process will be automatically simulated along the path.
With automatic planning function, the system will automatically find a collision-free assembly path from the current position to the designated position. (4) Records and replays of assembly processes: Useful assembly information, such as assembly sequences, assembly trajectories, positions and orientations of parts, are automatically recorded in assembly script files during assembling. And an assembly process is recorded in unit of assembly snippet which is designated by users. Then users can flexibly select the initiative snippet while replaying an assembly process. It is very useful for engineers to express and exchange assembly processes.
4. Tests To verify the practicability of FVAS, and the capabilities for supporting large-scale complex machines, such as nuclear facilities, we performed several tests using real-world engineering models. The test cases are conducted on a PC (central process unit (CPU) of Pentium IV 2.0 GHz, random access memory (RAM) of 1 GB, and graphics card RAM of 128 MB) with StereoGraphics emitters and CrystalEyes stereoscopic shutter glasses. In this paper, two of these test cases are presented to demonstrate the validity of this system in assembly planning and verification: (1) the Experimental Advanced Superconducting Tokamak (EAST) [4] constructed by China, and (2) the Fusion-Driven Sub-critical System (FDS-I) [5–7] designed by the FDS Team. The EAST Superconducting Tokamak is characterized by large volume, complicated structure, and high assembly precision, e.g. the gap in the three tori (the tori of vacuum vessel (VV), thermal shield (TS), and toroidal filed coil (TF)) is 20 mm. According to the final assembly plan, EAST assembly process is successfully reproduced on FVAS 1.0 based on its engineering CAD models Fig. 2 shows a scenario during assembling a one thirty second section thermal shield. In the figure, the current operated part grows red due to colliding with some other parts. So the operator should adjust the assembly trajectory. The red wire frame shows the final location of the current part. It is very useful for assembly navigation. The test results
P. Long et al. / Fusion Engineering and Design 82 (2007) 2062–2066
Fig. 2. A collision scenario during assembling EAST.
indicate that: (1) the rapid response during manually interactive virtual assembling verifies the real-time collision detection performance, (2) the assembly path planning function plays an important role in accelerating assembly progress and keeping assembly path regular, (3) the automatic path planning interface provides an efficient approach for exhibition of complicated assembly paths and verification of assemblability, and (4) 3 h and a half assembly record exhibits 5day virtual assembly process, and the over 2 years actual assembly process. The flexible assembly replay function provides a useful and efficient approach to express, exchange, and demonstrate assembly plans for engineers. Furthermore, FVAS 1.0 has been tested in the evaluation of FDS-I concept from assembly point of view (Fig. 3). Comparing with EAST, FDS-I is even bigger, and has a diameter of 18.6 m and a height of 16.5 m. And the test results validate the practicability of FVAS 1.0.
5. Summary FVAS is a VR based engineering application developed by the FDS Team, which aims to assist assembly planning and evaluation. FVAS 1.0 has been created, and the main capabilities have been realized. This paper gives an overview of FVAS 1.0’s architecture, main features and capabilities, and several test cases conducted
2065
Fig. 3. The display of trajectories while validating FDS-I’s assemblability.
using real-world engineering models. Test cases prove that FVAS 1.0 is efficient and practicable for simulation and analysis of assemblies with overhead crane as assembly tool. Now, the system is being improved to support kinematics simulation, physics properties, and collaborative assembly based on multi-users and multi-tools.
Acknowledgments The authors wish to thank all the members of FDS team. The work has been performed in the framework of knowledge innovation of the Chinese Academy of Sciences.
References [1] S. Kaufman, R. Wilson, R. Jones, T. Calton, A. Ames, The Archimedes 2 mechanical assembly planning system, in: Proceedings of the IEEE International Conference on Robotics and Automation, IEEE Press, Piscataway, NJ, 1996, pp. 3361–3368. [2] J. Wernecke, The Inventor Mentor: Programming ObjectOriented 3D Graphics with Open Inventor (TM), Release 2, Addison-Wesley, 1994. [3] S. Liu, X. Liu, Z. Liao, Collision detection methods based on VR-CAD applying to EAST virtual assembly simulation, J. Eng. Graph. 26 (2) (2005) 46–49. [4] Y. Wan, P. Weng, J. Li, Q. Yu, D. Gao, HT-7U Team, HT-7U Superconducting Tokamak: Physics design, engi-
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P. Long et al. / Fusion Engineering and Design 82 (2007) 2062–2066
neering progress and schedule, in: 19th IAEA Fusion Energy Conference, France, October 2002, 2002, pp. 14– 19. [5] Y. Wu, FDS Team, Conceptual design activities of FDS series fusion power plants in China [J], Fusion Eng. Des. 81 (2006) 2713–2718.
[6] Y. Wu, S. Zheng, X. Zhu, W. Wang, H. Wang, S. Liu, et al., Conceptual design of the fusion-driven subcritical system FDS-I [J], Fusion Eng. Des. 81 (2006) 1305–1311. [7] Y.C. Wu, J.P. Qian, J.N. Yu, The fusion-driven hybrid system and its material selection, J. Nucl. Mater. Part B 307–311 (2002) 1629–1636.
Design and testing of the Fusion Virtual Assembly System FVAS 1.0 P. Long ∗ , S. Liu, Y. Wu, the FDS Team Institute of Plasma Physics, Chinese Academy of Sciences, P.O. Box 1126, Hefei, Anhui 230031, China Received 31 July 2006; received in revised form 6 July 2007; accepted 6 July 2007 Available online 20 August 2007
Abstract This paper presents the Fusion Virtual Assembly System FVAS 1.0 which makes possible engineering application for assemblies of large-scale complex nuclear facilities. This system focuses on utilizing a desktop virtual environment tightly coupled with commercial Computer Aided Design (CAD) systems, and is designed to support assembly planning, evaluation, demonstration, and training, and to work on personal computer (PC) platform. Main features of FVAS include: (1) automatic assembly modeling, (2) separation of display scene and collision detection scene, (3) multi-way assembly planning, (4) records and replays of assembly processes. This paper describes the system architecture, features and capabilities of FVAS. And tests conducted using real-world engineering models are also described. © 2007 Elsevier B.V. All rights reserved. Keywords: Virtual assembly; Collision detection; Virtual roaming; Nuclear facility
1. Introduction Due to the complicated structure and high precision requirements of nuclear machines, detailed accurate assembling procedures must be planned before the practical assembly. However, assembly planning for complex systems has always been a difficult task for engineers. Although CAD systems allow configura∗ Corresponding author. Tel.: +86 551 559 3326; fax: +86 551 559 3326. E-mail address: [email protected] (P. Long).
0920-3796/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.fusengdes.2007.07.010
tion evaluation by letting engineers visualize the final assembly, these systems do not support the visualization or planning of the assembly process. Although many systems (such as the one described by Kaufman et al. [1]) are attempting to automate the planning process, it is very difficult to formalize assembly planners’ knowledge. Thus, physical prototypes are still the primary mode of planning and evaluating assembly processes. The development of applications of virtual reality (VR) in engineering has opened up a powerful array of tools to solve above problems. Virtual assembly
P. Long et al. / Fusion Engineering and Design 82 (2007) 2062–2066
(VA), utilizing VR technologies to plan and evaluate assembly processes, retains the benefits (time-saving, inexpensive, and no hazardous) of VR technologies and conquers the shortcoming of physical prototypes, such as long circle, high cost, low precision. Engineers can perform the assembly intuitively in the virtual environment using VR hardware and software. The Fusion Virtual Assembly System (FVAS) is a VR based engineering application which is designed to support planning, evaluation and demonstration of assembly processes, and assembly training, and to work on PC platform. This system has been implemented successfully and is being evaluated using test cases from real-world engineering. In this paper, we describe the system architecture, features and capabilities, and tests of FVAS.
2. Fusion Virtual Assembly System FVAS has been designed and implemented by the FDS Team using Visual C++ and Open Inventor [2] at ASIPP. The overall system concept is illustrated in Fig. 1. Once the engineer designs the mechanical system using any CAD system (e.g. Unigraphics), FVAS automatically imports the necessary data to the virtual environment through a user selected option. In the virtual environment, the user is presented with an assembly scene. The VR user can import various parts in the preassembly area, and then perform the assembly. This enables the user to explore and vali-
2063
date assembly processes, and perform a host of other engineering tasks in the virtual environment. The FVAS’s architecture is based on object-oriented design concepts and methods. There are seven main modules in the system: (1) ModelConverter: Converts parts’ CAD models into VR assembly models. (2) ViewpointsManager: Manages viewpoints, provides interface to manipulate the active viewpoint and to switch among all viewpoints, and realizes virtual roaming. (3) PartsManager: Manages all parts in the scene, and provides interface to manipulate parts. (4) CollisionManager: Provides real-time collision detection and response, and feeds back information used in the steps that follow to determine object movement. (5) AssPlanManager: Obtains and processes user input of data and commands, manages the human/computer interaction, and realizes assembly simulation. (6) AssReplayManager: Parses assembly script files, updates scene displays, and replays assembly processes. (7) AssemblyManager: Harmonizes all modules and the whole system, records the assembly process to script files. In above modules, PartsManager and CollisionManager are the core sections. AssPlanManager and AssReplayManager serve as the application inter-
Fig. 1. System architecture of FVAS.
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P. Long et al. / Fusion Engineering and Design 82 (2007) 2062–2066
face. The AssemblyManager is a bridge between core sections and application interface. And ModelConverter and ViewpointsManager are assistant modules.
3. Features and capabilities of FVAS (1) Automatic assembly modeling: Polygon-facet models of Mechanical Parts are needed for FVAS’s virtual environment. A CAD conversion utility program was written to translate CAD geometry files to VR assembly model files, which not only contain polygon-facet geometry information, but also include any assembly information used during assembling. (2) Separation of display scene and collision detection scene: To enhance the real-time performance of assembly simulation for large-scale nuclear facilities, a policy based on separation of display scene and collision detection scene has been adopted. The display scene can be predigested to reduce the time of scene refreshment, and the collision detection performance is greatly improved by using the mature interference check ability of commercial CAD systems.Convenient observation mechanism brings more practicability. So a multi-viewpoints roaming scheme has been utilized to facilitate users’ assembly operation in the display scene. Users can obtain much optical information from multiple angles by manipulating viewpoints.According to the Collision Detection Concept Based on VR-CAD [3], an improved VR-CAD based collision detection (CD) method is utilized to enhance the CD efficiency. With this method, the check number is reduced from (n − 1)n/2 to (n − 1) for a collision detection scene of n parts during one checking. (3) Multi-way assembly planning: Three assembly planning modes are supported in this system: (a) interactive virtual assembly, (b) assembly path planning, (c) automatic path planning. During interactive assembly, users can realistically manipulate virtual tools to perform assembly operations. An assembly path could be specified through the path-planning interface, and then the assembly process will be automatically simulated along the path.
With automatic planning function, the system will automatically find a collision-free assembly path from the current position to the designated position. (4) Records and replays of assembly processes: Useful assembly information, such as assembly sequences, assembly trajectories, positions and orientations of parts, are automatically recorded in assembly script files during assembling. And an assembly process is recorded in unit of assembly snippet which is designated by users. Then users can flexibly select the initiative snippet while replaying an assembly process. It is very useful for engineers to express and exchange assembly processes.
4. Tests To verify the practicability of FVAS, and the capabilities for supporting large-scale complex machines, such as nuclear facilities, we performed several tests using real-world engineering models. The test cases are conducted on a PC (central process unit (CPU) of Pentium IV 2.0 GHz, random access memory (RAM) of 1 GB, and graphics card RAM of 128 MB) with StereoGraphics emitters and CrystalEyes stereoscopic shutter glasses. In this paper, two of these test cases are presented to demonstrate the validity of this system in assembly planning and verification: (1) the Experimental Advanced Superconducting Tokamak (EAST) [4] constructed by China, and (2) the Fusion-Driven Sub-critical System (FDS-I) [5–7] designed by the FDS Team. The EAST Superconducting Tokamak is characterized by large volume, complicated structure, and high assembly precision, e.g. the gap in the three tori (the tori of vacuum vessel (VV), thermal shield (TS), and toroidal filed coil (TF)) is 20 mm. According to the final assembly plan, EAST assembly process is successfully reproduced on FVAS 1.0 based on its engineering CAD models Fig. 2 shows a scenario during assembling a one thirty second section thermal shield. In the figure, the current operated part grows red due to colliding with some other parts. So the operator should adjust the assembly trajectory. The red wire frame shows the final location of the current part. It is very useful for assembly navigation. The test results
P. Long et al. / Fusion Engineering and Design 82 (2007) 2062–2066
Fig. 2. A collision scenario during assembling EAST.
indicate that: (1) the rapid response during manually interactive virtual assembling verifies the real-time collision detection performance, (2) the assembly path planning function plays an important role in accelerating assembly progress and keeping assembly path regular, (3) the automatic path planning interface provides an efficient approach for exhibition of complicated assembly paths and verification of assemblability, and (4) 3 h and a half assembly record exhibits 5day virtual assembly process, and the over 2 years actual assembly process. The flexible assembly replay function provides a useful and efficient approach to express, exchange, and demonstrate assembly plans for engineers. Furthermore, FVAS 1.0 has been tested in the evaluation of FDS-I concept from assembly point of view (Fig. 3). Comparing with EAST, FDS-I is even bigger, and has a diameter of 18.6 m and a height of 16.5 m. And the test results validate the practicability of FVAS 1.0.
5. Summary FVAS is a VR based engineering application developed by the FDS Team, which aims to assist assembly planning and evaluation. FVAS 1.0 has been created, and the main capabilities have been realized. This paper gives an overview of FVAS 1.0’s architecture, main features and capabilities, and several test cases conducted
2065
Fig. 3. The display of trajectories while validating FDS-I’s assemblability.
using real-world engineering models. Test cases prove that FVAS 1.0 is efficient and practicable for simulation and analysis of assemblies with overhead crane as assembly tool. Now, the system is being improved to support kinematics simulation, physics properties, and collaborative assembly based on multi-users and multi-tools.
Acknowledgments The authors wish to thank all the members of FDS team. The work has been performed in the framework of knowledge innovation of the Chinese Academy of Sciences.
References [1] S. Kaufman, R. Wilson, R. Jones, T. Calton, A. Ames, The Archimedes 2 mechanical assembly planning system, in: Proceedings of the IEEE International Conference on Robotics and Automation, IEEE Press, Piscataway, NJ, 1996, pp. 3361–3368. [2] J. Wernecke, The Inventor Mentor: Programming ObjectOriented 3D Graphics with Open Inventor (TM), Release 2, Addison-Wesley, 1994. [3] S. Liu, X. Liu, Z. Liao, Collision detection methods based on VR-CAD applying to EAST virtual assembly simulation, J. Eng. Graph. 26 (2) (2005) 46–49. [4] Y. Wan, P. Weng, J. Li, Q. Yu, D. Gao, HT-7U Team, HT-7U Superconducting Tokamak: Physics design, engi-
2066
P. Long et al. / Fusion Engineering and Design 82 (2007) 2062–2066
neering progress and schedule, in: 19th IAEA Fusion Energy Conference, France, October 2002, 2002, pp. 14– 19. [5] Y. Wu, FDS Team, Conceptual design activities of FDS series fusion power plants in China [J], Fusion Eng. Des. 81 (2006) 2713–2718.
[6] Y. Wu, S. Zheng, X. Zhu, W. Wang, H. Wang, S. Liu, et al., Conceptual design of the fusion-driven subcritical system FDS-I [J], Fusion Eng. Des. 81 (2006) 1305–1311. [7] Y.C. Wu, J.P. Qian, J.N. Yu, The fusion-driven hybrid system and its material selection, J. Nucl. Mater. Part B 307–311 (2002) 1629–1636.