Doctor of Philosophy

dissertationVirtual environments provide a consistent and relatively inexpensive method of training individuals. They often include haptic feedback in the form of forces applied to a manipulandum or thimble to provide a more immersive and educational experience. However, the limited haptic feedback provided in these systems tends to be restrictive and frustrating to use. Providing tactile feedback in addition to this kinesthetic feedback can enhance the user's ability to manipulate and interact with virtual objects while providing a greater level of immersion. This dissertation advances the state-of-the-art by providing a better understanding of tactile feedback and advancing combined tactilekinesthetic systems. The tactile feedback described within this dissertation is provided by a finger-mounted device called the contact location display (CLD). Rather than displaying the entire contact surface, the device displays (feeds back) information only about the center of contact between the user's finger and a virtual surface. In prior work, the CLD used specialized two-dimensional environments to provide smooth tactile feedback. Using polygonal environments would greatly enhance the device's usefulness. However, the surface discontinuities created by the facets on these models are rendered through the CLD, regardless of traditional force shading algorithms. To address this issue, a haptic shading algorithm was developed to provide smooth tactile and kinesthetic interaction with general polygonal models. Two experiments were used to evaluate the shading algorithm. iv To better understand the design requirements of tactile devices, three separate experiments were run to evaluate the perception thresholds for cue localization, backlash, and system delay. These experiments establish quantitative design criteria for tactile devices. These results can serve as the maximum (i.e., most demanding) device specifications for tactile-kinesthetic haptic systems where the user experiences tactile feedback as a function of his/her limb motions. Lastly, a revision of the CLD was constructed and evaluated. By taking the newly evaluated design criteria into account, the CLD device became smaller and lighter weight, while providing a full two degree-of-freedom workspace that covers the bottom hemisphere of the finger. Two simple manipulation experiments were used to evaluate the new CLD device

A 3-D visualization of kirkpatrick's planar point location algorithm

info:eu-repo/semantics/publishe

Rock joint systems

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1985.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.Bibliography: p. 745-764.by William Simon Dershowitz.Ph.D