Effect of delays in softness display using contact area control: rendering of surface viscoelasticity

This paper discusses effects of delays in a softness display, which increase viscosity in the displayed tactile feelings. Previous softness reproductions based on contact area control used a static contact model to calculate contact area and thus did not consider dynamic contact behavior, such as delay. To discuss the delay and the resultant viscous feelings, this paper proposes a new dynamic contact model that extends the previous static model. The proposed dynamic contact model has a nonlinear damper and is verified by experiments that measure contact area on a real object. For the contact area measurement experiments, the work proposes a new sheet-type sensor specialized for contact area detection. Using the proposed contact model, control delays of the softness display is evaluated in comparison with the real object to find out the frequency limitation for correct reproduction of surface feelings. Finally, the paper proposes to implement a partially linearized dynamic contact model to the softness display to render feelings of viscoelastic objects.