Interactive project review of deformable parts through haptic interfaces in Virtual Reality

P prototypes are increasingly replaced by virtual prototypes in the industrial implementation of Product Lifecycle Management. The design evaluation of an industrial deformable mechanical part plays a crucial role in term of validating its functional properties. From the industrial point of view, a deformable model formulated by the Finite Element Method is normally employed. However, the employment of the model is not straightforward for real-time interactions, especially when haptic interfaces are introduced into these deformation evaluation applications. Recently, a pre-computation approach based on the model reduction method was commonly used to reduce the real-time computational loads. The main goal of this thesis is to extend the pre-computation approach toward the design validation of deformable mechanical parts to investigate the trade-off issue between the deformation accuracy and the interaction performance. The key idea is to conceive techniques treating the off-line pre-computations and the on-line haptic interactions. Particularly, we develop a real-time deformation simulation framework by proposing a two-stage method combining an off-line phase and an on-line phase. During the off-line phase, we compute deformation spaces based on the modal analysis. The off-line pre-computations contribute to the modelling of a costless real-time deformation model which is suitable for haptic interactions. Furthermore, we propose an off-line mesh analysis method to pre-compute modal deformation spaces regarding the anticipated deformation evaluation scenarios. A real-time switch among these different spaces is developed so that the on-line deformation computations can focus on degrees of freedom where are necessary. During the on-line phase, we divide the real-time deformation computation process into two separate modules which are implemented on different threads to ensure the real-time haptic interaction performance. One module is dedicated to the haptic update task, which is implemented by extracting a sub-matrix from the pre-computed modal matrix, while the other module is dedicated to the deformation computation and visualization task. To verify the proposed method in the thesis, we carry out interaction experiments by interacting with different models with an increasing complexity. Experimental results show that our method can efficiently handle the trade-off issue, as the deformation modelling is formulated by the finite element method which guarantees the deformation accuracy. And moreover, the heavy computations of large elastic systems are occurred off-line which assure a costless deformation response model in real-time.