Haptic manipulation of deformable CAD parts with a two-stage method

Real-time interaction between a designer and a deformable mock-up in Virtual Reality environments is a promising paradigm to evaluate design feasibilities. In this paper we focus on the haptic-aided deformation verification process of industrial deformable parts by combining small deformations and relatively large rigid-body motions. First, concerning the modelling process of small deformations, we propose a two-stage method extended from the linear modal analysis. In this two-stage method, modal deformation sub-spaces are pre-computed in an off-line phase, and real-time deformations are quickly reproduced by superimposing the responses of certain modes which are selected depending on interaction requirements. Based on this two-stage method, we propose a mesh analysis method to enrich the off-line pre-computations corresponding to different anticipated interaction scenarios. Furthermore, we apply a real-time division scheme which divides the deformation response process into two separate modules, so that stable haptic interactions are guaranteed. Second, concerning the purpose of global deformation verifications, we combine relatively large rigid-body motions resulting from the integration of classical motion equations and small deformations resulting from the aforementioned two-stage method. We have implemented the two-stage method to model small deformations and rigid-body motions. Real-time experiments are carried out by coupling a single haptic device with a simulation framework and experimental results validate the deformation accuracy on one hand, and demonstrate a good and stable haptic interaction experience on the other.