Graduation Year

2016

Document Type

Thesis

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Mechanical Engineering

Major Professor

Kyle B. Reed, Ph.D.

Co-Major Professor

Rasim Guldiken, Ph.D.

Committee Member

Nathan Crane, Ph.D.

Committee Member

Andres E. Tejada-Martinez, Ph.D.

Committee Member

Kristen Salomon, Ph.D.

Keywords

Thermal perception, Haptics, Constant cooling, Ther moelectric cooler, Finite element model, Thermal comfort

Abstract

The human body has a unique mechanism for perceiving surrounding temperatures. When an object is in contact with the skin, we do not feel its temperature. Instead, we feel the temperature change that is caused on our skin by that object. The faster the heat is transferred, the more intense the thermal sensation is. In this dissertation, a new dynamic thermal display method, where different rates of warm and cold are applied on the skin to generate a unique sensation, is presented. The new method can be related in a wide range of applications including thermal haptics and virtual reality.

To understand the perception of temperature and the general thermal state of the human body, the first aspect of this dissertation focuses on investigating the interaction between temperature change and perception on a large scale. Three field surveys were conducted inside airconditioned buildings to investigate the change in the thermal state and temperature perception of occupants when the room temperature changes. The results showed that the participants’ prediction of constant operating temperature was poor, however, their prediction was significantly improved when temperature changes were presented.

In order to more accurately investigate the perception of temperature on the skin, a new thermal display method using multiple-channel thermal actuators was developed. The principle of this method is to apply slow and fast rates of temperature change simultaneously on the skin. The slowly changing temperatures are below the perceptual threshold of the thermal receptors, therefore will not be detected whereas the quickly changing temperatures are above the perceptual threshold, hence, will be detected. The idea here is to keep the average surface temperature of the skin constant, however a person will perceive a sensation of continuous cooling. This method was tested through a series of experiments, and the results showed that it is capable of generating a continuous cooling sensation without changing the average temperature of the stimulation area. Multiple variations of this method were tested including different heating and cooling rates of change, different skin locations and patterns of stimuli. Also, a continuous warming was generated using similar concept.

To further investigate the temperature distribution that is caused by this method and its effect on the skin, a computational simulation was conducted. An approximate model of the skin was used to monitor its surface temperature and record the temperatures in the stimulation area when the continuous cooling method is applied. The results of the simulation showed that the temperature under the surface of the stimulation area was affected by the continuous cooling method that was applied on the skin model, however this method did not affect the average surface temperature of the skin. These findings may later determine the efficiency and intensity of the method of continuous cooling, and allow us to investigate different technically challenging variations of this method.

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