VIRTUAL REALITY TECHNOLOGIES AND VIRTUAL MANUFACTURING IN MANUFACTURING ENGINEERING

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1 VIRTUAL REALITY TECHNOLOGIES AND VIRTUAL MANUFACTURING IN MANUFACTURING ENGINEERING Jozef Novák-Marcinčin 1, Marcela Kuzmiaková 2, Khaled Al Beloushy 3 1,2,3 Technical University Košice, Faculty of Manufacturing Technologies in Prešov, Slovakia Abstract: The world environment around us provides a wealth of information that is difficult to duplicate in a computer. This is evidenced by the worlds used in virtual environments. Either these worlds are very simplistic such as the environments created for immersive entertainment and games, or the system that can create a more realistic environment has a million dollar price tag such as flight simulators. An augmented reality system generates a composite view for the user. It is a combination of the real scene viewed by the user and a virtual scene generated by the computer that augments the scene with additional information. Key words: virtual reality, virtual manufacturing, manufacturing engineering 1. INTRODUCTION With the advent of high-resolution graphics, high-speed computing, and user interaction devices, virtual reality (VR) has emerged as a major new technology in recent years. An important new concept introduced by many VR systems is immersion, which refers to the feeling of complete immersion in a three-dimensional computer-generated environment by means of user-centered perspective achieved through tracking the user. This is a huge step forward compared to classical modeling and CAD/CAM packages, which inherently impose major imitations on intuitive user interaction. VR technology is currently used in a broad range of applications, the best known being flight simulators, walkthroughs, video games, and medicine (virtual surgery). From a manufacturing standpoint, some of the attractive applications include training, collaborative product and process design, facility monitoring, and management. Moreover, recent advances in broadband networks are also opening up new applications for telecollaborative virtual environments in these areas. In this thesis I have chosen to cover certain areas which we believe to have a potentially significant impact on virtual manufacturing. This is still an evolving list and includes areas such as facility layout and work-cell management, real-time exact collision detection, motion modeling, avatar modeling, and virtual-real environment interaction in training, based on our years of experience in this field. In addition to these areas, the thesis explores some connections between VR and computer vision (especially camera self-calibration and stereo vision) in the context of depth recovery in virtual manufacturing. Some of the automation techniques resulting from these concepts can potentially reduce a lot of time and boredom for users involved in manually creating CAD-based virtual environments. Lately, with the emergence of complementary areas of VR such as augmented reality (AR), one can address crucial problems of registration between virtual and real worlds. 123

2 2. HISTORY OF VIRTUAL REALITY TECHNOLOGIES Historically, virtual reality has entered into the public awareness as medial toy with equipment helmet-glove, which was preferentially determined for wide public and the price of this system had also to correspond to this fact, so price could not be very high. As follows, the producers of virtual reality systems have aimed at developing and providing of the systems for data collecting and analysing and systems supporting economic modelling. It is obvious that, from among areas, where virtual reality systems can be most frequently used are applications based on 3D-space analysing and physical dimension visualisation. Virtual reality with ability to show data 3D and attach sounds and touch information increases extraordinarily data comprehensibility. Along with increasing the number of data are increased the effects from virtual reality too [6]. Let us have a short glimpse at the last three decades of research in virtual reality and its highlights [9]: Sensorama in years Morton Heilig created a multi-sensory simulator. A prerecorded film in color and stereo, was augmented by binaural sound, scent, wind and vibration experiences. This was the first approach to create a virtual reality system and it had all the features of such an environment, but it was not interactive. The Ultimate Display in 1965 Ivan Sutherland proposed the ultimate solution of virtual reality: an artificial world construction concept that included interactive graphics, force-feedback, sound, smell and taste. The Sword of Damocles the first virtual reality system realized in hardware, not in concept. Ivan Sutherland constructs a device considered as the first Head Mounted display (HMD), with appropriate head tracking. It supported a stereo view that was updated correctly according to the user s head position and orientation. VIDEOPLACE Artificial Reality created in 1975 by Myron Krueger a conceptual environment, with no existence. In this system the silhouettes of the users grabbed by the cameras were projected on a large screen. The participants were able to interact one with the other thanks to the image processing techniques that determined their positions in 2D screen s space. VCASS Thomas Furness at the US Air Force s Armstrong Medical Research Laboratories developed in 1982 the Visually Coupled Airborne Systems Simulator an advanced flight simulator. The fighter pilot wore a HMD that augmented the outthewindow view by the graphics describing targeting or optimal flight path information. VIVED VIrtual Visual Environment Display constructed at the NASA Ames in 1984 with off-the-shelf technology a stereoscopic monochrome HMD. VPL the VPL company manufactures the popular DataGlove (1985) and the Eyephone HMD (1988) the first commercially available VR devices. BOOM commercialized in 1989 by the Fake Space Labs. BOOM is a small box containing two CRT monitors that can be viewed through the eye holes. The user can grab the box, keep it by the eyes and move through the virtual world, as the mechanical arm measures the position and orientation of the box. Virtual Wind Tunnel developed in 1990s at the NASA Ames application that allowed the observation and investigation of flow-fields with the help of BOOM and DataGlove. CAVE presented in 1992 CAVE (CAVE Automatic Virtual Environment) is a virtual reality and scientific visualization system. Instead of using a HMD it projects stereoscopic images on the walls of room (user must wear LCD shutter glasses). This approach assures superior quality and resolution of viewed images, and wider field of view in comparison to HMD based systems. 124

3 Augmented Reality (AR) a technology that presents a virtual world that enriches, rather than replaces the real world. This is achieved by means of see-through HMD that superimposes virtual three-dimensional objects on real ones. Thanks to its great potential the enhancement of human vision augmented reality became a focus of many research projects in early 1990s. 3. BASIC APPLICATIONS OF VIRTUAL REALITY For a long time people have been gathering a great amount of various data. The management of megabytes or even gigabytes of information is no easy task. In order to make the full use of it, special visualization techniques were developed. Their goal is to make the data perceptible and easily accessible for humans. Desktop computers equipped with visualization packages and simple interface devices are far from being an optimal solution for data presentation and manipulation. Virtual reality promises a more intuitive way of interaction [1]. Fig. 1 VR in architecture: (a) Ephesos ruins, (b) reconstruction of destroyed Frauenkirche in Dresden (IBM). The first attempts to apply VR as a visualization tool were architectural walkthrough systems. The pioneering works in this field were done at the University of North Carolina beginning after year 1986, with the new system generations developed constantly. Many other research groups created impressive applications as well just to mention the visualization of St. Peter Basilica at the Vatican presented at the Virtual Reality World 95 congress in Stuttgart or commercial Virtual Kitchen design tool. What is so fantastic about VR to make it superior to a standard computer graphics? The feeling of presence and the sense of space in a virtual building, which cannot be reached even by the most realistic still pictures or animations. One can watch it and perceive it under different lighting conditions just like real facilities. One can even walk through non-existent houses the destroyed ones (Fig. 1) like e.g., the Frauenkirche in Dresden, or ones not even created yet. Another discipline where VR is also very useful is scientific visualization. The navigation through the huge amount of data visualized in three-dimensional space is almost as easy as walking. An impressive example of such an application is the Virtual Wind Tunnel, developed at the NASA Ames Research Center. Using this program the scientists have the possibility to use a data glove to input and manipulate the streams of virtual smoke in the airflow around a digital model of an airplane or space-shuttle. Moving around (using a BOOM display technology) they can watch and analyze the dynamic behavior of airflow and easily find the areas of instability (see Fig. 2). The advantages of such a visualization system are convincing it is clear that using this technology, the design process of complicated shapes of e.g., an aircraft, does not require the building of expensive wooden models any 125

4 more. It makes the design phase much shorter and cheaper. The success of NASA Ames encouraged the other companies to build similar installations at Eurographics 95 Volkswagen in cooperation with the German Fraunhofer Institute presented a prototype of a virtual wind tunnel for exploration of airflow around car bodies. Fig. 2 Exploration of airflow using Virtual Wind Tunnel developed at NASA Ames: (a) outside view, (b) inside view Other disciplines of scientific visualization that have also profited of virtual reality include visualization of chemical molecules (see Fig. 3), the digital terrain data of Mars surface etc. Fig. 3 VR in chemistry: exploration of molecules Augmented reality (see Fig. 4) offers the enhancement of human perception and was applied as a virtual user s guide to help completing some tasks: from the easy ones like laser printer maintenance to really complex ones like a technician guide in building a wiring harness that forms part of an airplane s electrical system. An other example of augmented reality application was developed at the UNC: its goal was to enhance a doctor s view with ultrasonic vision to enable him/her to gaze directly into the patient s body. Fig. 4 Augmented Reality: (a) idea of AR, (b) augmented reality manufacturing system 126

5 4. VIRTUAL MANUFACTURING The combination of information technology (IT) and production technology has greatly changed traditional manufacturing industries. Many manufacturing tasks have been carried out as information processing within computers. For example, mechanical engineers can design and evaluate a new part in a 3D CAD system without constructing a real prototype. As many activities in manufacturing systems can be carried out using computer systems, the concept of virtual manufacturing (VM) has now evolved [2]. VM is defined as an integrated synthetic manufacturing environment for enhancing all levels of decision and control in a manufacturing system. VM is the integration of VR and manufacturing technologies. The scope of VM can range from an integration of the design sub-functions (such as drafting, finite element analysis and prototyping) to the complete functions within a manufacturing enterprise, such as planning, operations and control. VM systems are integrated computer-based models that represent the precise structures of manufacturing systems and simulate their physical and informational behavior in operation. VM technology has achieved much in reducing manufacturing cost and time-tomarkcl, leading to an improvement in productivity. Much research effort to conceptualize and construct a VM system has been reported. Onosato and Iwata (1993) generated the concept of a VM system and Kimura (1993) described the product and process model of a VM system. Based on the concept and the model, a general modeling and simulation architecture for a VM system was developed by Iwata et al. (1995). Ebrahimi and Whalley (1998) developed a cutting force prediction model for simulating machining conditions in VM. A virtual machining laboratory for knowledge learning and skills training was implemented by Fang et al. (1998). In the virtual machining laboratory, both comprehensive knowledge learning and physical skills training can be achieved in an interactive synthetic environment. Using headmounted stereo glasses and interactive gloves, students can virtually operate a lathe or set machining parameters and input CNC G-code program to cut the work-piece automatically, Machining process performance, such as machining conditions, cutting forces, cutting power, surface roughness and tool life, can also be simulated with the machining process evaluation models. Fig. 5 Simulation of virtual workplaces activity During a VM simulation process, 3D graphics or VR will be an enabling tool to improve human-to-human or human-to-machine communications. VM addresses the collaboration and integration among distributed entities involved in the entire production process. However, VM is regarded as evolutionary rather than revolutionary. It employs computer simulation, which is not a new field, to model products and their fabrication processes, and aims to improve the decision-making processes along the entire production cycle. Networked VR plays an essential role in VM development. 127

6 Current VR and Web technologies have provided the feasibility to implement VM systems. However, this is not an easy task due to the following factors [2]: The conflicting requirements of real-time machining and rendering. Generally, a high level of detail for a scene description would result in a high complexity of the virtual scene. The conflicting requirements of static data structure and dynamic modeling. In the virtual machining environment, a dynamically modeled workpiece is essential. The requirements for a consistent environment to avoid confusion and provide navigational cues to prevent a user from getting lost in the VR environment. The importance of an adequate sense of immersion in the VR environment, without which even a highly detailed rendering will not help a user interact effectively in the virtual 3D environment using conventional 2D interfaces such as a keyboard. 5. CONCLUSION Virtual reality and virtual manufacturing often concentrate on an interface between VR technology and manufacturing and production theory and practice. In this thesis we concentrate on the role of VR technology in developing this interface. It is our belief that the direction of evolution of manufacturing theory and practice will become clearer in the future once the role of VR technology is understood better in developing this interface. Ministry of Education of SR supported this work, contract VEGA No. 1/0036/09 with title Optimization of mechanical technological processes by use of devices and technique of augmented virtual reality technologies. 6. REFERENCES [1] BANERJEE, P. - ZETU, D.: Virtual Manufacturing. John Wiley and Sons, New York, 320 pp., ISBN [2] JEDRZEJEWSKI J.- KWASNY W.: Remarks on state-of-the-art Virtual Manufacturing. In: Virtual manufacturing. Wroclaw university of Technology, Wroclaw, 2001, p [3] KURIC I. - KOŠTURIAK J. - JANAČ A. - PETERKA J.- MARCINČIN J.N.: Computer Aided Systems in Mechanical Engineering. EDIS ŽU, Žilina, 2002, 351 s. (in Slovak). [4] LEDERER G.: Virtual Manufacturing - Manufacturers Challenge of the 1990s. CIME - Computer Integrated Manufacture and Engineering. Vol. 1, No. 2, 1996, pp [5] MARCINČIN, J. N.: Computer Aided Manufacturing and Virtual Manufacturing - History and Present Time. Informatyka, organizacja i zarzadzanie. Nr. ser. 3, zeszyt Nr. 13, ATH Bielsko-Biala, 2004, pp , ISSN [6] MARCINČIN, J. N. - BRÁZDA, P.: Virtual Reality and Augmented Reality in Technologies. Automation and CA Systems in Technology Planning and in Manufacturing (Editor: S. Legutko). Vol. 5, No. 1, Poznan - Giewartow, 2004, pp , ISSN [7] MAZURYK, T. - GERVAUTZ, M.: Virtual Reality: History, Applications, Technology and Future. Vienna University of Technology, Vienna. [8] NEAGA, I. - KURIC, I.: Virtual Environments for Product Design and Manufacturing. In: Proceedings CA Systems and Technologies. Žilina, 1999, pp [9] ONG, S. K. - NEE, A. Y. C.: Virtual and Augmented Reality Applications in Manufacturing. Springer- Verlag London, 387 pp., ISBN [10] VALLINO, J.: Introduction to Augmented Reality. Rochester Institute of Technology, Rochester, 2002 ( 128