Integration and disruption effects of shape and texture in haptic search

In a search task, where one has to search for the presence of a target among distractors, the target is sometimes easily found, whereas in other searches it is much harder to find. The performance in a search task is influenced by the identity of the target, the identity of the distractors and the differences between the two. In this study, these factors were manipulated by varying the target and distractors in shape (cube or sphere) and roughness (rough or smooth) in a haptic search task. Participants had to grasp a bundle of items and determine as fast as possible whether a predefined target was present or not. It was found that roughness and edges were relatively salient features and the search for the presence of these features was faster than for their absence. If the task was easy, the addition of these features could also disrupt performance, even if they were irrelevant for the search task. Another important finding was that the search for a target that differed in two properties from the distractors was faster than a task with only a single property difference, although this was only found if the two target properties were non-salient. This means that shape and texture can be effectively integrated. Finally, it was found that edges are more beneficial to a search task than disrupting, whereas for roughness this was the other way round

Relative sensation of wetness of different materials

Previous studies have already shown that an illusion of wetness can be elicited by touching a dry cold object. Both metal and cloth are materials that can cause this illusion. This paper investigated the relative sensation of wetness caused by some other materials at the same low temperature. Participants were presented with stimulus pairs of different materials such as metal, PVC, acrylic and paper, and they had to judge which of the two felt wetter. From the results we obtained a scale of relative wetness sensation. Subsequently, several physical properties of the materials were measured. We conclude that materials that cause the human skin to cool quickly, cause the stimulus to feel relatively wet. Interestingly, also stickiness can lead to a sensation of relative wetness, even when presented at room temperature

Haptic perception of force magnitude and its relation to postural arm dynamics in 3D

In a previous study, we found the perception of force magnitude to be anisotropic in the horizontal plane. In the current study, we investigated this anisotropy in three dimensional space. In addition, we tested our previous hypothesis that the perceptual anisotropy was directly related to anisotropies in arm dynamics. In experiment 1, static force magnitude perception was studied using a free magnitude estimation paradigm. This experiment revealed a significant and consistent anisotropy in force magnitude perception, with forces exerted perpendicular to the line between hand and shoulder being perceived as 50% larger than forces exerted along this line. In experiment 2, postural arm dynamics were measured using stochastic position perturbations exerted by a haptic device and quantified through system identification. By fitting a mass-damper-spring model to the data, the stiffness, damping and inertia parameters could be characterized in all the directions in which perception was also measured. These results show that none of the arm dynamics parameters were oriented either exactly perpendicular or parallel to the perceptual anisotropy. This means that endpoint stiffness, damping or inertia alone cannot explain the consistent anisotropy in force magnitude perception.W Mugge ten tijde van uitkomen artikel werknemer TU Delft (UD tenure track). Artikel heeft geen TU Delft-affiliatie. Vandaar 2 werkrelaties aangegeven en "not eligible" bij SEP output typeBiomechatronics & Human-Machine Contro

"Haptic material": A Holistic Approach for Haptic Texture Mapping

International audienceIn this paper, we propose a new format for haptic texture mapping which is not dependent on the haptic rendering setup hardware. Our "haptic material" format encodes ten elementary haptic features in dedicated maps, similarly to "materials" used in computer graphics. These ten different features enable the expression of compliance, surface geometry and friction attributes through vibratory, cutaneous and kinesthetic cues, as well as thermal rendering. The diversity of haptic data allows various hardware to share this single format, each of them selecting which features to render depending on its capabilities

A High-Fidelity Surface-Haptic Device for Texture Rendering on Bare Finger

We present the design and evaluation of a high fidelity surfacehaptic device. The user slides a finger along a glass plate while friction is controlled via the amplitude modulation of ultrasonic vibrations of the plate. A non-contact finger position sensor and low latency rendering scheme allow for the reproduction of fine textures directly on the bare finger. The device can reproduce features as small as 25 μm while maintaining an update rate of 5 kHz. Signal attenuation, inherent to resonant devices, is compensated with a feedforward filter, enabling an artifact-free rendering of virtual textures on a glass plate

Harmonious textures: The perceptual dimensions of synthetic sinusoidal gratings

International audienceNatural gratings explored by a finger generate vibratory patterns. These vibrations contain a wide range of frequencies, which include the fundamental spatial frequency of the grating and other (higher) harmonics. In this study, it was proposed to investigate how the fundamental and harmonic frequencies contribute to the perception of a virtual grating presented in the form of spatial pattern of friction force. Using multidimensional scaling methods, we established that the first overtone was the main characteristic used by the participants to identify gratings. When asked to rate the pleasantness to the touch, participants' preferences were for gratings with low spatial frequencies and low amplitudes. These results suggest new ways of creating meaningful, pleasant human-computer interactions in the context of surface-haptic displays