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A learning environment for maintenance of power equipment using virtual reality
Symbiosis of Human and Artifact Y. Anzai, K. Ogawa and H. Mori (Editors) © 1995 Elsevier Science B.V. All rights reserved.
441
A Learning Environment for Maintenance of Power Equipment using Virtual Reality Shotaro Miwa, Takao Ueda, Masanori Akiyoshi, Shogo Nishida CENTRAL RESEARCH LABORATORY, MITSUBISHI ELECTRIC CORPORATION 1-1, TSUKAGUCHI-HONMACHI 8-CHOME, AMAGASAKI, HYOGO 661 JAPAN Abstract
This paper deals with a learning environment for maintenance of power equipment using Virtual Reality. First of all, the insights of cognitive science and the analysis of maintenance expertise are discussed from the viewpoint of understanding support system. Then design philosophy of the learning environment is proposed based on the analysis. The prototype system is designed and implemented using both EWS(Engineering WorkStation) and GWS(Graphic WorkStation). This prototype system is applied to the maintenance of the Gas Insulated Substation, which is one of power equipment, and its performance is evaluated through demonstration. I. Introduction
Progress of software technology of a computer has made it possible to facilitate access to multimedia information, such as text, sounds and graphics. Also, progress of hardware technology has produced new I/O devices, such as a gesture-inputting-device, a large high-resolution display and so on. Against the background of such progress, newly emerging technology called Virtual Reality is expected to provide a powerful interactive environment between human and computers[ 1]. On the other hand, many CAI(computer-assisted instruction) systems have been developed[2], and it is pointed out that a prerequisite for designing an effective learning environment is to clarify how we understand our world and develop our mental model. Since Virtual Reality technology has sense appeal as if we are embedded in the environment, we believe this feature makes it possible to construct a new learning environment beyond present CAI systems. In this paper, we propose a Virtual Reality learning environment for maintenance of power equipment. As a preliminary investigation, insights on human ways of understanding and maintenance expertise are analyzed. Then the requisites are pointed out, and the design philosophy of the learning environment is proposed.
442
2. Design Concept 2.1. Human Ways of Understanding As for human ways of understanding, the following points are important. • Understanding from multiple viewpoints When we try to understand something, we change our viewpoints. We understand completely by integrating such multiple viewpoints. Therefore it is important to provide a student with an environment, where he can change and find a viewpoint to help his own understanding. •Evolution in understanding Understanding is a ever-lasting process where we have some questions and find a solution[3]. This process leads to understanding deeply. And what is important for this process is a situation where he is confronted with a subject[4]. An environment that a student himself can make trial and error makes it possible to promote this understanding process.
2.2. Maintenance Expertise As for maintenance expertise, the following points are important. • Concrete knowledge on operations An operator needs to know contents of each maintenance step. For instance, he has to know a component's name and how to handle it. Furthermore he has to execute practical operations correctly on the maintenance spot • Network-like knowledge of the whole maintenance task An operator not only understands each maintenance step, but also he needs to understand flow of maintenance. For instance, he needs to know correlation of subsequent maintenance steps. • Causal understanding on mechanism To cope with unexpected situations, he should know mechanism of operational components with knowledge of maintenance task.
2.3. Requisites of the System From the above analysis, the requisites are pointed out as follows. • Visualization of a structure representing the expertise of experienced operators, and indication of significance of each step of the maintenance task • Reality in operational situations • Support for understanding correlation between maintenance knowledge and practical operations • Free exploration promoting situated understanding These requisites are realized in our learning environment using Virtual Reality.
443 3. A Learning Environment for Maintenance of Power Equipment Based on the above investigation we built a learning environment of power equipment using Virtual Reality. A system configuration and system functions are described in the following two sections. 3.1. System Configuration The above requisites are realized by using Virtual Reality and our information visualizing tool. This tool manages some attributes of maintenance expertise using 3D graphics, in which network structure is used for representing the learning data on maintenance expertise. Fig.1 shows the system configuration, which consists of EWS(engineering workstation), GWS(graphic workstation), and Control unit. The EWS manages the learning data and provides a pedagogical interface using four subwindows; for instance, indication of significance. The GWS manages 3D stereo graphics, which provide Virtual Reality with the aid of liquid-crystal glasses and a DataGlove. The Control unit manages a communication channel between EWS and GWS so that data from GWS changes the displayed information on EWS, and vice versa.
global window
i n fc~rmatlr~ n
window liquid-crystal glasses stereoscopic display
lima
DataGlove local win(
0 EWS
RS232C[ Control Unit ] Ethernet
GWS
Fig. 1 System configuration 3.2. System Functions System functions are described in the following three subsections. 3.2.1. EWS Fig.1 shows a window of EWS. The window is composed of four subwindows. Each subwindow has the following function.
444 • Global window This window shows the whole structure of the learning data. Each step of the maintenance task is represented in a colored cube that varies in size. The color depends on the significance grade in the maintenance task; for instance, danger items are shown in red. The size depends on the complexity grade; for instance, a large cube is used if operators have to disassemble some component for checking. The current maintenance step is marked with white wireframe box. • Local window The local window provides a detailed information on the current maintenance step, in which text explains the sequence of practical operations. • Information window This window shows which category of faults operators are checking; for instance, malfunction of power supply, malfunction of machinery and so on. • Map window This window provides spatial information on the maintenance site, in which an operator' s current position is marked with an arrow.
3.2.2. GWS The GWS manages 3D stereo graphics. It provides the following learning environment. • A learning environment which provides free exploration A student walks around a virtual environment, and for instance, he can disassemble some components and see inner mechanism. • Correlation between maintenance steps and practical operations The GWS shows virtual scenes that correspond to sequences of maintenance steps on EWS. Therefore a student easily understand practical maintenance situations.
3.3. Example We applied this system to the maintenance task of GIS(Gas Insulated Substation). Fig.2 shows an example of learning data. Suppose that an alarm message in the control room occurs. In this case, the categories of faults are divided into three kinds of faults, such as malfunction of
main control room
spot
! i
equipment
,,
control box '
:
main body
,
,,
[
II
II
DS is disabled. ''~y
Turn the direct-distant switch to direct.
| !
• maintenance task
i |
~
• flow
DS: Disconnecting Switch
Fig.2 An example of maintenance operationsfor power equipment
445 wiring, malfunction of power supply, and malfunction of machinery. The alarm message says that there is a problem about disconnecting switch. At first, an operator checks the malfunction of wiring. He goes to a control box, and change the mode of switch from a distant control to a direct control. He tries to directly make the disconnecting switch work on the spot, and proceed to a subsequent step. Fig.3 shows an example of virtual scene that comes into an operator's sight. Fig.4 shows a display of EWS. Realized functions are as follows.
Fig.3 An examle of virtual scenes on GWS
Fig.4 Pedagogical interface on EWS
• Grasp of the multiple aspects of each maintenance task When a student selects the first step in the global window, wireframe boxes are shown in both information window and map window. For instance, in the information window, a node labeled disconnecting switch and a node labeled malfunction of wiring are surrounded by wireframe. In the map window, a node labeled control box is surrounded by wireframe. This shows a category of faults and a component to investigate. In the local window, detailed text information of maintenance task is shown. EWS shows these information in four subwindows, and he knows multiple aspects of each maintenance task easily. • Grasp of whole maintenance task from multiple viewpoints Maintenance steps are displayed by cubes in the global window. X-axis shows flow of maintenance procedures. Y-axis shows names of components for maintenance. And Z-axis shows categories of faults. A student also grasps importance and meaning of each step of the maintenance task from colors and sizes of cubes. For instance, a red cube warns a student that it is a dangerous maintenance step for a high voltage component, or a large cube tells that it is a little complicated step to use a measuring tool. A global window can be rotated for arbitrary view. A student can find a viewpoint which helps to get information of categories of faults, or importance of each maintenance step. • Reality in operational situations Each maintenance step is related with practical operations in a virtual environment. In the global window of EWS, a student selects a maintenance step. Then, in a virtual environment, he
446 can go to the maintenance spot, find a component for the maintenance, and execute the practical operations. • Walkthrough in the virtual environment A student can walk through in the virtual environment. His location is monitored by EWS, and an alert message is displayed on EWS if an operator approaches a high voltage component. Furthermore, an operator can investigate internal mechanisms of virtual components that are invisible in the real world. Due to this visualization, he can understand components deeply and also execute operations with conviction. 3.4. Evaluation
By demonstrating the system, we collected subjective opinions as follows. (1) Positive opinions • Displaying the whole structure of learning data with 3D graphics is effective. • Free exploration and operations in the virtual environment is considered to enhance operators' understanding. (2) Constructive opinions to improve the system • Interface with force feedback is desirable. • Speedy movement from one place to another is needed for realism. • It is more useful if simulation models are implemented in the virtual world. 4. Condusion
This paper describes a learning environment for maintenance of power equipment using Virtual Reality. Our design concept is to support developing operators' mental model based on the investigations of insights on human cognition and the maintenance expertise. The system is now under evaluation, and is considered to be effective through demonstration. REFERENCES
1. C. Blanchard, S. Burgess, Y. Harvill, J. Lanier, A. Lasko, M. Oberman and M. Teitel, "Reality Built for Two: A Virtual Reality Tool", Computer Graphics, Vol.24, No.2, pp.35-36(1990) 2. D. Sleeman and J. S. Brown (eds.), "Intelligent Tutoring Systems", Academic Press, London(1982) 3. Y. Saeki(eds.), "What is the understanding?", Tokyo University Publishing Association(1985)(Japanese) 4. Y. Saeki, "Computer and Education", Iwanami Publishing(1986)(Japanese)
441
A Learning Environment for Maintenance of Power Equipment using Virtual Reality Shotaro Miwa, Takao Ueda, Masanori Akiyoshi, Shogo Nishida CENTRAL RESEARCH LABORATORY, MITSUBISHI ELECTRIC CORPORATION 1-1, TSUKAGUCHI-HONMACHI 8-CHOME, AMAGASAKI, HYOGO 661 JAPAN Abstract
This paper deals with a learning environment for maintenance of power equipment using Virtual Reality. First of all, the insights of cognitive science and the analysis of maintenance expertise are discussed from the viewpoint of understanding support system. Then design philosophy of the learning environment is proposed based on the analysis. The prototype system is designed and implemented using both EWS(Engineering WorkStation) and GWS(Graphic WorkStation). This prototype system is applied to the maintenance of the Gas Insulated Substation, which is one of power equipment, and its performance is evaluated through demonstration. I. Introduction
Progress of software technology of a computer has made it possible to facilitate access to multimedia information, such as text, sounds and graphics. Also, progress of hardware technology has produced new I/O devices, such as a gesture-inputting-device, a large high-resolution display and so on. Against the background of such progress, newly emerging technology called Virtual Reality is expected to provide a powerful interactive environment between human and computers[ 1]. On the other hand, many CAI(computer-assisted instruction) systems have been developed[2], and it is pointed out that a prerequisite for designing an effective learning environment is to clarify how we understand our world and develop our mental model. Since Virtual Reality technology has sense appeal as if we are embedded in the environment, we believe this feature makes it possible to construct a new learning environment beyond present CAI systems. In this paper, we propose a Virtual Reality learning environment for maintenance of power equipment. As a preliminary investigation, insights on human ways of understanding and maintenance expertise are analyzed. Then the requisites are pointed out, and the design philosophy of the learning environment is proposed.
442
2. Design Concept 2.1. Human Ways of Understanding As for human ways of understanding, the following points are important. • Understanding from multiple viewpoints When we try to understand something, we change our viewpoints. We understand completely by integrating such multiple viewpoints. Therefore it is important to provide a student with an environment, where he can change and find a viewpoint to help his own understanding. •Evolution in understanding Understanding is a ever-lasting process where we have some questions and find a solution[3]. This process leads to understanding deeply. And what is important for this process is a situation where he is confronted with a subject[4]. An environment that a student himself can make trial and error makes it possible to promote this understanding process.
2.2. Maintenance Expertise As for maintenance expertise, the following points are important. • Concrete knowledge on operations An operator needs to know contents of each maintenance step. For instance, he has to know a component's name and how to handle it. Furthermore he has to execute practical operations correctly on the maintenance spot • Network-like knowledge of the whole maintenance task An operator not only understands each maintenance step, but also he needs to understand flow of maintenance. For instance, he needs to know correlation of subsequent maintenance steps. • Causal understanding on mechanism To cope with unexpected situations, he should know mechanism of operational components with knowledge of maintenance task.
2.3. Requisites of the System From the above analysis, the requisites are pointed out as follows. • Visualization of a structure representing the expertise of experienced operators, and indication of significance of each step of the maintenance task • Reality in operational situations • Support for understanding correlation between maintenance knowledge and practical operations • Free exploration promoting situated understanding These requisites are realized in our learning environment using Virtual Reality.
443 3. A Learning Environment for Maintenance of Power Equipment Based on the above investigation we built a learning environment of power equipment using Virtual Reality. A system configuration and system functions are described in the following two sections. 3.1. System Configuration The above requisites are realized by using Virtual Reality and our information visualizing tool. This tool manages some attributes of maintenance expertise using 3D graphics, in which network structure is used for representing the learning data on maintenance expertise. Fig.1 shows the system configuration, which consists of EWS(engineering workstation), GWS(graphic workstation), and Control unit. The EWS manages the learning data and provides a pedagogical interface using four subwindows; for instance, indication of significance. The GWS manages 3D stereo graphics, which provide Virtual Reality with the aid of liquid-crystal glasses and a DataGlove. The Control unit manages a communication channel between EWS and GWS so that data from GWS changes the displayed information on EWS, and vice versa.
global window
i n fc~rmatlr~ n
window liquid-crystal glasses stereoscopic display
lima
DataGlove local win(
0 EWS
RS232C[ Control Unit ] Ethernet
GWS
Fig. 1 System configuration 3.2. System Functions System functions are described in the following three subsections. 3.2.1. EWS Fig.1 shows a window of EWS. The window is composed of four subwindows. Each subwindow has the following function.
444 • Global window This window shows the whole structure of the learning data. Each step of the maintenance task is represented in a colored cube that varies in size. The color depends on the significance grade in the maintenance task; for instance, danger items are shown in red. The size depends on the complexity grade; for instance, a large cube is used if operators have to disassemble some component for checking. The current maintenance step is marked with white wireframe box. • Local window The local window provides a detailed information on the current maintenance step, in which text explains the sequence of practical operations. • Information window This window shows which category of faults operators are checking; for instance, malfunction of power supply, malfunction of machinery and so on. • Map window This window provides spatial information on the maintenance site, in which an operator' s current position is marked with an arrow.
3.2.2. GWS The GWS manages 3D stereo graphics. It provides the following learning environment. • A learning environment which provides free exploration A student walks around a virtual environment, and for instance, he can disassemble some components and see inner mechanism. • Correlation between maintenance steps and practical operations The GWS shows virtual scenes that correspond to sequences of maintenance steps on EWS. Therefore a student easily understand practical maintenance situations.
3.3. Example We applied this system to the maintenance task of GIS(Gas Insulated Substation). Fig.2 shows an example of learning data. Suppose that an alarm message in the control room occurs. In this case, the categories of faults are divided into three kinds of faults, such as malfunction of
main control room
spot
! i
equipment
,,
control box '
:
main body
,
,,
[
II
II
DS is disabled. ''~y
Turn the direct-distant switch to direct.
| !
• maintenance task
i |
~
• flow
DS: Disconnecting Switch
Fig.2 An example of maintenance operationsfor power equipment
445 wiring, malfunction of power supply, and malfunction of machinery. The alarm message says that there is a problem about disconnecting switch. At first, an operator checks the malfunction of wiring. He goes to a control box, and change the mode of switch from a distant control to a direct control. He tries to directly make the disconnecting switch work on the spot, and proceed to a subsequent step. Fig.3 shows an example of virtual scene that comes into an operator's sight. Fig.4 shows a display of EWS. Realized functions are as follows.
Fig.3 An examle of virtual scenes on GWS
Fig.4 Pedagogical interface on EWS
• Grasp of the multiple aspects of each maintenance task When a student selects the first step in the global window, wireframe boxes are shown in both information window and map window. For instance, in the information window, a node labeled disconnecting switch and a node labeled malfunction of wiring are surrounded by wireframe. In the map window, a node labeled control box is surrounded by wireframe. This shows a category of faults and a component to investigate. In the local window, detailed text information of maintenance task is shown. EWS shows these information in four subwindows, and he knows multiple aspects of each maintenance task easily. • Grasp of whole maintenance task from multiple viewpoints Maintenance steps are displayed by cubes in the global window. X-axis shows flow of maintenance procedures. Y-axis shows names of components for maintenance. And Z-axis shows categories of faults. A student also grasps importance and meaning of each step of the maintenance task from colors and sizes of cubes. For instance, a red cube warns a student that it is a dangerous maintenance step for a high voltage component, or a large cube tells that it is a little complicated step to use a measuring tool. A global window can be rotated for arbitrary view. A student can find a viewpoint which helps to get information of categories of faults, or importance of each maintenance step. • Reality in operational situations Each maintenance step is related with practical operations in a virtual environment. In the global window of EWS, a student selects a maintenance step. Then, in a virtual environment, he
446 can go to the maintenance spot, find a component for the maintenance, and execute the practical operations. • Walkthrough in the virtual environment A student can walk through in the virtual environment. His location is monitored by EWS, and an alert message is displayed on EWS if an operator approaches a high voltage component. Furthermore, an operator can investigate internal mechanisms of virtual components that are invisible in the real world. Due to this visualization, he can understand components deeply and also execute operations with conviction. 3.4. Evaluation
By demonstrating the system, we collected subjective opinions as follows. (1) Positive opinions • Displaying the whole structure of learning data with 3D graphics is effective. • Free exploration and operations in the virtual environment is considered to enhance operators' understanding. (2) Constructive opinions to improve the system • Interface with force feedback is desirable. • Speedy movement from one place to another is needed for realism. • It is more useful if simulation models are implemented in the virtual world. 4. Condusion
This paper describes a learning environment for maintenance of power equipment using Virtual Reality. Our design concept is to support developing operators' mental model based on the investigations of insights on human cognition and the maintenance expertise. The system is now under evaluation, and is considered to be effective through demonstration. REFERENCES
1. C. Blanchard, S. Burgess, Y. Harvill, J. Lanier, A. Lasko, M. Oberman and M. Teitel, "Reality Built for Two: A Virtual Reality Tool", Computer Graphics, Vol.24, No.2, pp.35-36(1990) 2. D. Sleeman and J. S. Brown (eds.), "Intelligent Tutoring Systems", Academic Press, London(1982) 3. Y. Saeki(eds.), "What is the understanding?", Tokyo University Publishing Association(1985)(Japanese) 4. Y. Saeki, "Computer and Education", Iwanami Publishing(1986)(Japanese)