The aspects of adequate simulation of the flexible parts for path planning during the Assembly/Disassembly (A/D) operation simulation are discussed in this paper. An interactive system forming two complementary levels and incorporating mechanical models of flexible part is described. The approach proposed will be used as a basis to the simulation of flexible parts into a Virtual Reality (VR) environment for the A/D evaluation. First of all, the study of current assembly path planning systems is performed. Secondly, as an issue of the problems discussed, a new system integrating real-time and interactive mechanical simulation approaches is proposed. Finally, an example of the interactive mechanical behavior model applicable to flexible rods used into an A/D path planning context is presented. Numerical modeling focuses on typical boundary conditions. The present approach is considered as a proposal for a methodology used with VR environments during the product design process.

The Digital Mock-Up (DMU), which is a comprehensive numerical model describing the final manufactured product, is today widely used in the industry (like the automotive and aeronautic industries) to support the concurrent engineering organizations and processes. On the other hand, simulation helps in the development of a product for design decision making or validation purposes. It allows to determine, with the appropriate level of accuracy, the behavior of the future product under a specific environment or set of exterior actions. Virtual Reality (VR) applications are simulations where the focus is on immersion and interaction with the product. However, there is still lacks in the integration of simulation within the product development phases. In particular the link between the DMU and the numerical models for simulation in the large is often hardly achieved. For some types of simulation, it is even inexistent. In this paper, we propose a new object, the Downstream Digital Mock-Up (DDMU), based on a polyhedral representation, and we show that it can be a support for the integration of a subset of simulation activities within the product development process by making the link between the DMU and these simulations. In the particular case of VR, we show that this object is particularly adapted. One particularity of the DDMU is to be prepared for a specific target application, defined by its objectives and the context in which it is immersed.

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Fast simulation of Assembly/Disassembly (A/D) operations is important to improve quickly the performance and quality of products. However, it is difficult to model accurately the A/D operations of products containing flexible parts given their complex mechanical behavior. To evaluate the A/D of flexible parts in order to provide better responses in terms of design, maintenance, ergonomics, a user needs criteria characterizing A/D operations. The aim of this work is to propose some of these criteria based on geometric and physical parameters. The realistic values of these parameters are coupled to an adequate behavior model of flexible parts and can be used in virtual A/D simulations. So, as an issue of current A/D approach problems, the requirements for integration of the Interactive Mechanical Model (IMM) into a virtual A/D system are discussed. An example of flexible beam IMM providing the realistic data is presented. The use of non-linear IMMs raises questions regarding the boundary conditions required to model a user’s action during a virtual A/D operation simulation. To this end, physical and numerical experiments have been performed using an optical tracking system. From these experiments, the necessary parameters can be extracted to characterize both real and virtual A/D operations.

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