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Cross-cutting Challenges - Theme 2: Interactive Discussions
Cross-cutting Challenges
California East
Sensing Materials Thermally
Lynette A. Jones
(Massachusetts Institute of Technology, USA)
Abstract: The changes in skin temperature that occur when the hand makes contact with an object provide information about the thermal properties of the object and these in turn assist in identifying the material composition of the object. In order to recreate these sensations in virtual environments or teleoperated robotic systems, thermal feedback has been incorporated in haptic displays. The objective of the display is to assist in object recognition in situations in which visual information may be limited or absent, and to create a more realistic experience of the contact between the hand and the object in a virtual environment. Thermal displays that assist in object identification typically consist of thermal stimulators, thermal sensors, and a temperature control system that monitors and controls the surface temperature of the thermal display. The results from a number of experiments have demonstrated that the thermal cues presented by such displays convey sufficient information to enable users to identify and discriminate between materials with a level of accuracy that is comparable to that achieved with real materials. Thermal displays have been incorporated into tactile displays with the aim of presenting a more realistic sensory experience of objects in virtual or remote environments. In these multisensory displays, thermal feedback provides information about the material composition of virtual objects and vibrotactile feedback conveys surface texture cues. Information regarding changes in skin temperature is relayed to the cerebral cortex in pathways that are separate from those that convey information about mechanical stimulation of the skin. In order to create effective multi-sensory displays, it is important to understand how these two sensory pathways interact. Results from recent experiments in which vibrotactile stimulation has been delivered concurrently with thermal stimuli indicate that vibration can have a substantial effect on the ability to identify thermal patterns. These studies demonstrated that dynamic tactile stimuli have a greater effect on thermal pattern identification than a continuous signal. Interestingly, vibrotactile stimulation had a greater effect on the perception of cold than warmth. This is an intriguing finding that is of particular relevance to perceiving the properties of objects in that most objects in contact with skin are at ambient temperature, and so it is the decrease in skin temperature that provides cues about the object’s material composition. The challenge in designing multi-sensory cutaneous displays is understanding such interactions and optimizing the temporal and spatial properties of stimulus presentation so that the user perceives a single perceptual entity and not independent sources of information.

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Time stamp: 2019-03-26T19:36:58+01:00