While it is known that softness discrimination relies on both kinesthetic and cutaneous information, relatively little work has been done on the realization of haptic devices replicating the two cues in an integrated and effective way. In this paper, we first discuss the ambiguities that arise in unimodal touch, and provide a simple intuitive explanation in terms of basic contact mechanics. With this as a motivation, we discuss the implementation and control of an integrated device, where a conventional kinesthetic haptic display is combined with a cutaneous softness display. We investigate the effectiveness of the integrated display via a number of psychophysical tests and compare the subjective perception of softness with that obtained by direct touch on physical objects. Results show that the subjects interacting with the integrated haptic display are able to discriminate softness better than with either a purely kinesthetic or a purely cutaneous display.
"They should also be acoustically silent and generate low heat, so as to favor comfort for the user. In order to overcome the typical inability of pneumatic and electromagnetic drives to meet all these requirements (Minamizawa et al., 2007; Scilingo et al., 2010), new actuation technologies are needed. "
[Show abstract][Hide abstract] ABSTRACT: We describe here a wearable, wireless, compact, and lightweight tactile display, able to mechanically stimulate the fingertip of users, so as to simulate contact with soft bodies in virtual environments. The device was based on dielectric elastomer actuators, as high-performance electromechanically active polymers. The actuator was arranged at the user's fingertip, integrated within a plastic case, which also hosted a compact high-voltage circuitry. A custom-made wireless control unit was arranged on the forearm and connected to the display via low-voltage leads. We present the structure of the device and a characterization of it, in terms of electromechanical response and stress relaxation. Furthermore, we present results of a psychophysical test aimed at assessing the ability of the system to generate different levels of force that can be perceived by users.
Frontiers in Bioengineering and Biotechnology 09/2014; 2:31. DOI:10.3389/fbioe.2014.00031
"Further, slippery or sticky surfaces can be presented by tangentially deforming the finger pads     without modifying the actual frictional properties of the tactors. With the aim of presenting virtual softness simplistically, Bicchi and Scilingo et al.  , Fujita et al. , and Kimura et al.  proposed displays that controlled the contact area between the human finger pad and the tactor. Electric tactile displays also have the potential to function as simple texture displays without any mechanical structures  . "
[Show abstract][Hide abstract] ABSTRACT: For industrial purposes such as product design, texture displays should deliver a quality sense of touch to users. We have developed a vibrotactile texture display that uses real materials such as fabric, wood, and leather to enable the presentation of quality textures to users. By applying two types of vibrotactile stimuli to users’ finger pads through the materials, their fine and macro roughness sensations can be selectively modified while maintaining their original perceptual characteristics. This approach is effective for different types of textures such as paper, wood, leather, and cloth unless they possess strong damping properties that may attenuate the vibratory stimuli applied through them.
"Humans integrate both skin and proprioceptive sensations to estimate the properties of an object while exploring it with their fingers. For example, these two sensations provide information about the weight , , , hardness , , and length  of the object. Furthermore, links between these two sensations have been suggested to play a role in the perception of the surface shape , . "
[Show abstract][Hide abstract] ABSTRACT: Humans perceive a force applied to their fingertips by integrating skin and proprioceptive sensations. In this study, we investigated the relative contribution ratios of these sensations using two approaches. Decoupled forces were applied to the finger pad and proximal interphalangeal joint of the index finger of the participants. First, we calculated the ratios from the point of subjective equality between the skin and the proprioceptive perceptions. Second, we obtained discrimination limens of the two perceptions to compute their contribution ratios. The results of these two approaches showed good agreement. Additionally, we investigated how the magnitudes of forces, which were 1.0 and 0.3 N, applied to a fingertip affect the relative contribution ratios of the two sensory channels. When humans perceived the force of 1.0 N, the relative contribution ratios of skin and proprioceptive sensations were 16–28% and 72–84%, respectively. In contrast, when humans perceived the force of 0.3 N, the relative contribution ratios were 37–55% and 45–63%, respectively. These relative contribution ratios can be utilized for the design of efficient haptic interfaces.
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