In this study, we developed vibrotactile display methods that can assist designers in product design. In order to achieve realistic sensations required for such designing purposes, we used real materials such as cloth, paper, wood, and leather and applied vibrotactile stimuli to modify the roughness sensations of these materials. This approach allowed us to present textures of various virtual materials with a strong sense of reality. We verified that our proposed methods could selectively modify the fine and macro-roughness sensations of real materials. The methods are expected to aid product designers in deciding tactile sensations suitable for their products.
In this study, we set out to develop a method for estimating the fine and fast shear deformation of a finger pad, that is, the palm side of a fingertip, as it scans the surface of a material. Using a miniature accelerometer, we measured the acceleration at the radial skin, the deformation of which is accompanied by the shear deformation of the finger pad. Using a transfer function, as specified in a separate experiment, between the pad and side of a finger, we estimated the shear deformation of the finger pad in the frequency domain. A comparison between an estimate based on the accelerometer and another based on a precise force sensor for the tangential component of the interaction force between the fingertip and material surfaces showed that the estimation accuracy was sufficient for frequencies in excess of approximately 20-50 Hz and for skin deformation above 10 −6 m. Our technique merely requires that an accelerometer be attached to the side of the fingertip, which allows active texture exploration. These estimates or measurements of the finger skin deformation caused by touching materials will help us to comprehend the relationships between material surfaces and the resulting texture sensations.
Measuring the shear deformation of a finger pad during active haptic exploration of materials is important for analysis of textural sensations and development of tactile texture displays. Thus far, there has been no general methods to measure such deformations for active touch. To create a sensor system, we have been developing a new method for estimating the deformation of a finger pad based on the skin deformation propagated to the radial side of a finger tip. In this study, in order to validate the method, we compared the deformation or its acceleration of finger pad estimated on the basis of the acceleration measured at the radial side and those estimated by the shear force applied to the finger pad while exploring a few types of materials. The estimation errors for the deformations at 40-450 Hz were smaller than human discrimination thresholds, indicating that the accuracy of our method is satisfactory compared with human perceptual sensitivity.
A vibrotactile texture display produces virtual textures by applying vibratory stimuli to finger pads. In this study, we developed a technique to alter such textures based on certain specified materials. For example, the technique allows us to alter vibrotactile textures using terms such as "wood-," "cotton-," or "paper-like" which are familiar to end users of displays. The altered textures feel more similar to these specified materials. We realized this technique by constructing a material space, in which the materials are located based on the features of their vibrotactile spectra. The vibrotactile textures were then modified in this space. Our experimental results show that the technique can be used to alter a virtual wood texture to feel like cloth.
The dependence of the formation of surface roughness in Si on the incident angle of the Cs+ primary ion in secondary ion mass spectrometry is reported. No ripples formed in the analytical crater bottom when the primary ion incident angle was from 0° to 30° for sputtered depths of less than 4 μm, but ripples were observed when the incident angle was from 45° to 75°. The depth of ripple formation became shallower with the incident angle increasing. Cross sections of ripples observed by a scanning electron microscope and a transmission electron microscope suggest that ripples grow by forming facets from those plane faces with the largest sputtering rates so that the shapes of the facets remain constant during sputtering.
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