Thesis (Ph. D.)--Ohio State University, 2003. / Title from first page of PDF file. Document formatted into pages; contains xiii, 102 p.: ill. (some col.). Includes abstract and vita. Advisor: Roger A. Crawfis, Dept. of Computer and Information Science. Includes bibliographical references (p. 98-102).

Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (leaves 83-87).

published_or_final_version / abstract / Architecture / Doctoral / Doctor of Philosophy

The purpose of the study was to examine the efficacy of virtual reality exposure therapy (VRET) to treat driving phobia using a multiple baseline across-subjects design. The sequence of events included a pre-treatment assessment, a baseline phase, 8 weekly VRET sessions using a standardized treatment protocol, a post-treatment assessment, and 1- and 3-month follow-up assessments. A sample of seven treatment seeking adults with a primary diagnosis of specific phobia (driving) was recruited. Five completed the treatment and follow-up phases. One individual withdrew after the pre-treatment assessment, and the other, after the first treatment session. It was hypothesized that VRET would reduce driving anxiety and avoidance symptoms between pre- and post-treatment assessments using several outcome measures. Visual and statistical analysis methods were used to assess treatment outcome. Three participants showed clear improvement in driving anxiety and avoidance symptoms between pre- and post-treatment assessments. There was a marginal improvement in these symptoms for one participant. The remaining participant showed very little improvement, and some outcome measures revealed slight deterioration in some of her symptoms. There was negligible change in actual driving frequency in any participant. Some gains were lost at the 1- and 3-month follow-up assessments, but symptoms remained far below pre-treatment results. Possibilities for future research and practice implications are discussed.

Restoration of realistic animation is a critical part in the area of computer graphics. The goal of this sort of simulation is to imitate the behavior of the transformation in real life to the greatest extent. Physics-based simulation provides a solid background and proficient theories that can be applied in the simulation. In this dissertation, I will present real-time simulations which are physics-based in the area of terrain deformation and ship oscillations. When ground vehicles navigate on soft terrains such as sand, snow and mud, they often leave distinctive tracks. The realistic simulation of such vehicle-terrain interaction is important for ground based visual simulations and many video games. However, the existing research in terrain deformation has not addressed this issue effectively. In this dissertation, I present a new terrain deformation algorithm for simulating vehicle-terrain interaction in real time. The algorithm is based on the classic terramechanics theories, and calculates terrain deformation according to the vehicle load, velocity, tire size, and soil concentration. As a result, this algorithm can simulate different vehicle tracks on different types of terrains with different vehicle properties. I demonstrate my algorithm by vehicle tracks on soft terrain. In the field of ship oscillation simulation, I propose a new method for simulating ship motions in waves. Although there have been plenty of previous work on physics based fluid-solid simulation, most of these methods are not suitable for real-time applications. In particular, few methods are designed specifically for simulating ship motion in waves. My method is based on physics theories of ship motion, but with necessary simplifications to ensure real-time performance. My results show that this method is well suited to simulate sophisticated ship motions in real time applications.

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This thesis falls into the field of tactile displays that are meant to produce realistic tactile sensations, which replicate tactile sensations arising naturally when humans interact with the real world. / To begin with we need to know the biomechanics of the glabrous skin in human subjects. To this end, small patches of fingerpad skin are tested in vivo for their biomechanical properties under tangential loading. The skin is quasi-statically stretched and sheared to obtain its effective Young's modulus. Moreover, isotonic and isometric testing conditions are implemented to identify the viscoelasticity model of the skin. The results show a great deal of variability across subjects and it is observed that the glabrous skin exhibits nonlinear stiffening in tangential traction. The skin is consistently more elastic across the ridges, compared to along the ridges, regardless of the location of the sample on the fingerpad. The skin behaves visco-elastically but relaxes about twice as fast as it creeps. Finally, it is found that under large deformation, there is consistently 80% of hysteretic loss for a wide range of loading conditions. / Based on the results obtained by controlled testing, a high performance distributed display is designed. The display has a compact, yet modular structure. Its 6x10 piezo bimorph actuator array has a spatial resolution of 1.8x1.2 millimeters and a wide temporal bandwidth. The actuator mounting method is improved from conventional cantilever to dual-pinned lever, giving the actuator the capability of optimally coupling with glabrous skin. By using previously measured biomechanical data of the skin, we tune the parameters of the actuators to be optimal in terms of real deflection when they couple with the skin. The blocked force of the individual actuators can be adjusted from 0.15 N to 0.22 N to accommodate different applications. It is self-contained in a 150 cm3 volume and may be interfaced to most computers, provided that two analog outputs and six digital IO lines are available. Both public demonstration and psychophysical experiments have validated its effectiveness in rendering virtual tactile features. / The availability of a display raises the question of what signals should be used to drive it in order to render specific sensations. Some progress is made in this direction by analyzing the contact mechanics of fundamental cases, such as isolated indentation and traveling undulation. With the intention of explaining a tactile illusion engendered by straining the fingertip skin tangentially in a progressive wave pattern, resulting in the perception of a moving undulating surface, we carry out a contact mechanics analysis to derive the strain tensor field induced by a sinusoidal surface sliding on a finger, as well as the field created by a tactile transducer array deforming the fingerpad skin by lateral traction. We find that the first field can be well approximated by the second. Our results imply that, first, tactile displays using lateral skin deformation can generate tactile sensations similar to those using normal skin deformation. Second, there is a synthesis approach to achieve this result given constraints on the design of tactile stimulators. Third, the mechanoreceptors embedded in the skin must respond to the deviatoric part of the strain tensor field and not to its volumetric part. Finally, many tactile stimuli might represent for the brain an inverse problem to be solved. / Using the results of these investigations, we have demonstrated the feasibility of producing high-fidelity virtual tactile sensations.

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