A Model that Predicts the Material Recognition Performance of Thermal Tactile Sensing

Tactile sensing can enable a robot to infer properties of its surroundings, such as the material of an object. Heat transfer based sensing can be used for material recognition due to differences in the thermal properties of materials. While data-driven methods have shown promise for this recognition problem, many factors can influence performance, including sensor noise, the initial temperatures of the sensor and the object, the thermal effusivities of the materials, and the duration of contact. We present a physics-based mathematical model that predicts material recognition performance given these factors. Our model uses semi-infinite solids and a statistical method to calculate an F1 score for the binary material recognition. We evaluated our method using simulated contact with 69 materials and data collected by a real robot with 12 materials. Our model predicted the material recognition performance of support vector machine (SVM) with 96% accuracy for the simulated data, with 92% accuracy for real-world data with constant initial sensor temperatures, and with 91% accuracy for real-world data with varied initial sensor temperatures. Using our model, we also provide insight into the roles of various factors on recognition performance, such as the temperature difference between the sensor and the object. Overall, our results suggest that our model could be used to help design better thermal sensors for robots and enable robots to use them more effectively.Comment: This article is currently under review for possible publicatio

Influence of contact conditions on thermal responses of the hand

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009.Includes bibliographical references (leaves 82-87).The objective of the research conducted for this thesis was to evaluate the influence of contact conditions on the thermal responses of the finger pad and their perceptual effects. A series of experiments investigated the thermal and perceptual effects of different contact conditions including contact force, contact duration, the object's surface temperature, and its surface roughness. The thermal response of the finger pad was measured using an infrared camera as the contact force varied from 0.1 to 6 N. It was determined that the decrease in skin temperature was highly dependent on the magnitude of contact force as well as contact duration. A second set of experiments investigated the effect of surface texture on the thermal response of the finger pad, and demonstrated, contrary to predictions, that a greater change in skin temperature occurs when the finger is in contact with rougher surfaces. The effect of varying surface texture on the perception of temperature was also investigated. The changes in temperature due to varying surface texture are perceptible, and demonstrate that the perception of surface roughness is not only influenced by changes in temperature, but in turn affects the perception of temperature. The final set of experiments examined the effect of varying the surface temperature of the thermal display on the perceived magnitude of finger force. Over the range of 20 to 38 'C, the surface temperature of the display did not have a significant effect on the perceived magnitude of force. The results of these experiments can be incorporated into thermal models that are used to create more realistic displays for virtual environments and teleoperated systems.by Jessica Anne Galie.S.M

Development and evaluation of a thermal model for haptic interfaces

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.Includes bibliographical references (leaves 147-152).The thermal interaction between the skin and an object is influenced by the thermal properties and initial temperatures of the skin and object, and by the contact force and surface roughness of the contact surfaces. This thermal interaction is modeled in this research which characterizes the transient thermal responses during contact. The thermal model was evaluated in psychophysical and physiological experiments by determining whether simulated thermal feedback generated based on the model was capable of conveying information to users that was similar to that provided by real materials, and by comparing the temperature responses of the skin predicted by the model and elicited by real materials. In order to obtain precise skin temperature measurements, an infrared thermal measurement system was designed to overcome the limitations imposed by thermal sensors and to determine the influence of contact pressure on the skin temperature responses during contact. The results from the psychophysical and physiological experiments validated the thermal model proposed in this research within the typical contact force range of manual exploration. A thermal display based on this model is able to convey thermal cues that can be used to perceive and identify objects as effectively as those provided by real materials.by Hsin-Ni Ho.Ph.D

The Assessment of Practical Per-Cooling Targeting Peripheral Limbs During Exercise in Hot and Humid Environments

When excess body heat generation owing to the performance of exercise coincides with the heat dissipation limitations presented by hot and humid environments, the body’s ability to maintain thermal balance is compromised, and internal temperatures can rise to dangerous levels. Individuals who exercise in hot environments commonly look to acute cooling strategies to provide thermoregulatory assistance in order to avoid the health risks and performance decrements brought about by elevated thermal stress. Many cooling techniques aim to apply cold surfaces to large areas of skin on the torso, head, or neck to extract heat directly from core regions of the body. These locations, however, are often difficult to access without disrupting movement. In many exercise modalities including cycling, paddle sports, or wheelchair sports, however, peripheral regions such as the upper or lower limbs remain almost stationary, and may present a convenient location to apply cooling garments/equipment without disrupting required movements. The research studying the impact of practically applicable cooling techniques at these locations, however, is limited and inconclusive, prompting the present work. This document first outlines the quantifiable heat transfer principles that determine human thermal behaviour, and discusses the effects of thermal stress and acute cooling interventions. It then outlines practical considerations regarding the applications of cooling techniques, motivating the proposal of a novel technique that does not interfere with exercise performance by targeting the volar forearm skin of cyclists during exercise. The impacts of forearm cooling are then assessed experimentally during cycling ergometry exercise in a hot and humid environment. The cooling was observed to reduce the rate of core temperature rise by 0.43 ± 0.34°C/hr (p=0.002), while also eliciting significant reductions in heart rate drift and rating of thermal comfort. Computational modelling of the human thermal system was then employed to extend the experimental investigation and assess what impact the cooling may have during true cycling applications outside of the laboratory setting. Model outcomes suggest that the effects of the outdoor environment may reduce the effectiveness of the applied cooling slightly, but that the cooling will still be capable of providing quantifiable benefits. The impact of the cooling was also simulated across a range of ambient conditions, and the cooling was generally observed to be more impactful in hotter air temperatures and at higher ambient humidity levels