Université d'Evry: Thermal record and replay Thermal rendering can enhance the feeling of Presence in direct touch situations. For including this percept in the Person-to-Object scenario, first Université d'Evry had to find out how important thermal rendering is in distinguishing between different materials. Therefore, researchers at the Laboratoires Systèmes Complexes performed a study on multimodal perception and discrimination. The subject’s task was to identify seven different materials (Wood, Steel, Brass, Marble, Copper, Plexiglas and Aluminum). Thermal and visual cues were given – the first were presented as real material cubes the second as pictures (from these cubes) via computer display. Visual cues provide a very precise and dominant impression of our environment. In virtual reality settings visual feedback seems to be the most important kind of feedback. To create a more realistic and vivid virtual environment, other feedback modalities can be integrated, for example thermal feedback. Under normal conditions the haptic exploration of materials creates a feeling of cooling on the skin which is a result of a heat flow from the warm dermis into the cooler material. The aim of the study was first to find a baseline for human visual identification performance of a set of materials and to compare this performance to a second performance baseline when only thermal information is presented. Then, it should be examined if a benefit exists in discrimination performance when both modes are displayed together. Furthermore the researchers investigated how subjects react to ambiguous haptic information: in those trials visual and thermal properties displayed were from two different materials. In conclusion, the research group found that the discrimination ability of subjects is much higher when visual information is presented compared to single thermal information. Multimodal information did not significantly increase subject’s identification performance in this case. For the incongruent stimuli, the ratio congruent to incongruent stimuli did not significantly change subject’s judgments. It should be noted that in the case of more congruent information (group 2), the amount of visual judgments is the same as the amount of correct classifications in the unimodal visual condition. This leads to the conclusion that thermal information is not considered here or does not provide any additional information about the material. The handling times across the conditions were very similar with a mean between 19 and 17seconds. Only the unimodal visual condition was processed much faster with 4.70seconds. The slightly faster processing in the congruent condition especially for group 2 confirms the above finding, that if visual information is present and matches mostly with the thermal information, the identification is done quicker. At present Université d'Evry is developing design criteria of thermal interfaces. The research aims at enhancing the quality of thermal rendering in real and virtual telepresence environments. So far the following results could be achieved: Modeling and identification of thermoelectric modules: The researchers proposed models describing the behavior of Peltier thermoelectric modules for both steady-state and unsteady-state dynamics; these models are based on recursive ARMA models for temperature and heat flux. The proposed models are convenient for simulation, control, electronic, and thermal engineers. They also help understanding the functionality of the heat pumps, and facilitate the solving of cooling/heating problems without the need for expertise in thermal engineering. The effectiveness of the models and the synthesized controller are assessed by simulation and experimentally. Learning-based thermal rendering in telepresence To reproduce realistic thermal sensations, Université d'Evry has proposed a new approach based on a learning technique using real measurements of thermal heat flux exchanged during contact between operator finger and several materials. The candidates' materials are chosen so that they have dissimilar thermal properties. This technique reduces the difficulties in determining the thermal contact resistance because this resistance is not needed, since the use of complex mathematical models is avoided; it can also be used to avoid a sensing system different from fingertip thermal properties. The identification of the material in the operating site allows the generation of the adequate desired heat flux. The percentage of good classification depends on the length of the temporal sequence used for learning and/or for validation and the performance of the rendering depends on the instant and the type of contact. Also, the constructed databases may be used for studying the evolution of the contact heat flux and determining the thermal parameters of the touched object. To validate this approach, an experimental setup has been realized and a set of experiments performed. The obtained results are encouraging and allow the improvement of the thermal rendering in the future work in order to get more realistic sensations when exploring or manipulating remote objects via haptic interfaces.

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