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Distributed Virtual Prototyping


Devices like a keyboard, a mouse, and/or a data-glove are used in most cases for navigation and manipulation purposes. These provide either a very abstract or a quite intuitive but very limited interface, caused by the fairly small reaching space of the human's arm with respect to the possible workspace. Moreover they usually allow only single-handed interaction with the virtual environment. This is despite the fact that, just as in real life, two-handed operations in most cases are the optimum when interacting with 3D-graphics. Indeed when humans can make use of both hands, they usually do. In order to make a step towards to overcome these difficulties, a new two-handed input device was developed, exploiting the SPACE MOUSE® technology developed by the German Aerospace Center as starting point. The device incorporates a high-resolution graphic display, together with two 6-DOF controllers, one at each side of the screen. It enables the user to steer around virtual objects, over arbitrary distance and rotations, in an intuitive way. The purpose of the device is not to provide a completely realistic impression while interacting with 3D-objects (like haptic devices), but it shall provide easy and untiring manipulation and navigation inside virtual environments. To use the device it is not necessary for the user to learn abstract motion control commands that one than transmits to the device. It is only necessary to push at the controller caps just so as one would do with a real object that is to be moved. It is therefore a desirable input device for every virtual reality application. It can be applied in single-handed or two-handed mode. The single-handed mode can be used to assemble two parts by moving each part by one controller. The two-handed mode is useful to perform assembly tasks with long objects or to steer flexible objects. This capability to support also two-handed interaction makes it especially qualified for assembly and disassembly applications.
The key feature of the assembly simulator is the ability to assemble and disassemble of CAD parts using direct interaction techniques and geometric constraints. This assembly simulator brings together many features such as surface based collision detection, automatic constraint recognition and deletion, kinematic simulation within a single software framework to provide a novel interactive design assessment approach. The potential applications of this assembly simulator are numerous. This assembly simulator can be used by various sectors such as automotive, aerospace, process industry and general engineering to assess assembly capabilities, assembly sequence and maintainability during design or for training maintenance engineers. The innovative feature of this assembly simulator is the ability to simulate physical tasks within a virtual environment using direct interaction techniques and physical constraints. This assembly simulator overcomes the weaknesses of current VR systems and offers a virtual paradigm to perform precise manipulations required by engineers to perform assembly assessment of products. Current CAD systems are now well matured to support the detailed design stages of a product. However, they lack support for assessing down stream processes such as assembly and maintenance. This assembly simulator provides a solution for supporting such down stream process within an immersive or non-immersive virtual environment. The use of this module, integrated within their current CAD solution, will allow companies to assess assembly and maintenance processes and reduce life cycle costs of products.
One of the major drawbacks of current virtual environments is the unrealistic behaviour of the manipulated parts. Even if there is the possibility to assign physical properties like a mass to them and to check for collisions between them, they are still commonly modelled as rigid bodies. But there are a lot of parts like pipes, wires, and cables that in fact are deformable. Thus to create simulations that are as close to reality as possible the virtual objects also have to be deformable. Because of this one part of the DIVIPRO project consisted in the development and implementation of computational models of deformable thread-like bodies for use in virtual reality scenarios. Reviewing the latest results in rod mechanics it was realised that available solution methods are not or only partially usable in context of real-time virtual reality applications. That is why two new approaches for the shape calculation of deformable thread-like bodies were developed. The first developed approach (shooting approach) uses a shooting method in combination with an explicit ODE-solver of Runge Kutta type to solve the underlying differential equations and is able to adapt the discretisation grid to the occurring deformations in order to save computational resources, while the other approach (elastic chain approach) is based on an elastic multi-body system model. Numerical tests demonstrated the efficiency and accuracy of the developed methods. It was observed that the elastic chain approach performs slower but also more stable. Moreover the developed methods were embedded into a multi-body scenario in order to be able to handle possibly occurring contacts with other bodies.