Haptic Interaction with Deformable Objects: Modelling VR Systems for Textiles (Springer Series on Touch and Haptic Systems)

Haptic Interaction with Deformable Objects: Modelling VR Systems for Textiles (Springer Series on Touch and Haptic Systems)

Guido Böttcher

Language: English

Pages: 140

ISBN: 144712684X

Format: PDF / Kindle (mobi) / ePub

The focus from most Virtual Reality (VR) systems lies mainly on the visual immersion of the user. But the emphasis only on the visual perception is insufficient for some applications as the user is limited in his interactions within the VR. Therefore the textbook presents the principles and theoretical background to develop a VR system that is able to create a link between physical simulations and haptic rendering which requires update rates of 1\, kHz for the force feedback. Special attention is given to the modeling and computation of contact forces in a two-finger grasp of textiles. Addressing further the perception of small scale surface properties like roughness, novel algorithms are presented that are not only able to consider the highly dynamic behaviour of textiles but also capable of computing the small forces needed for the tactile rendering at the contact point. Final analysis of the entire VR system is being made showing the problems and the solutions found in the work

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the curve S(γ (s)) : R → M is arc length parameterised. Assuming further the textile surface does not vary much in local shear strain, the length of the first derivation of the surface curve ∂t∂ S(γ (t)) is equal in length of the derivative in parameter space ∂t∂ γ (t) . This is supported by the fact that tense threads are generally not curved and thus finding γ satisfying ∂t∂ γ (t) = 1 is comparatively easy. The easily found discrete differential operators by the aforementioned assumptions are

where particles have direct influence on each other. These non-zero entries are related to the elements that have been defined by the force functions in Sect. 2.3.3. But since the elements have a very small stencil on the textile mesh, the matrix is very sparse. At an iteration step of the CG method one can even more reduce the memory consumption by computing the blocks when they are needed to for the multiplication with the search vector. Having such small memory requirements can drastically

himself. Then the VR system tries to compute the forces or positions that a user would receive due to his actions as an immediate result of the current configuration in the VE. The computed signals are displayed by a so-called haptic device. For the computation as well as for the design of such devices, it is useful to consider the characteristics of our touch sense to provide the illusion of touch is provided by a haptically augmented VR system. 3.1.1 Touch Perception The human perception

created at the egression. By increasing the sampling frequency of the system it is possible to reduce the aforementioned effects. But due to limited computing power, such an approach is certainly undesirable and thus not suitable for complex simulations. Instead of that [14] proposes two solutions to the problem. In the first approach, the position is extrapolated for a the half of a time step in advance in order to compute a mean in force between the actual and the next time step. The second

including the contact force at the touch of the rigid support, and the second ensures the fulfilment of the kinematic constraint for the contact. Solving for the multiplier yields λ = kh − mg = fr (3.37) Despite the expression of the contact with Lagrange multipliers, it is still necessary to check for contact by fr > 0. When no contact is detected, i.e. fr equals zero, then the inequality constraint is disregarded as the multiplier vanishes. Another common method to consider contact problems

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