Force Shading for Shape Perception in Haptic Virtual Environments.

摘要

This thesis proposes a novel haptic rendering algorithm and describes two experiments that demonstrate its effectiveness in causing humans to perceive shapes in haptic virtual environments. Haptic rendering algorithms control haptic interfaces, the robotic devices which enable manual interaction between humans and virtual environments. The algorithm proposed in this thesis, called force shading, refers to a controlled variation in the direction of the force vector output by the haptic renderer for the purpose of creating the illusion of a non-flat shape on a nominally flat surface. The two experiments, a matching experiment and a classification experiment, were done on 5 subjects. In the matching experiment, subjects were asked to change the size of a virtual 'matching' bump until it matched a virtual 'reference' bump. The reference bump was always a circular cylinder, while the matching bump was either another circular cylinder or one of three force shaded polyhedral approximations. As the number of polygons increased in the polyhedral approximations, the subjects' performance approached their performance in matching cylinders. Even for the nominally flat surface with force shading, subjects correlated their matching radii with the reference radii. When visual stimuli was added to the polyhedral approximations, performance was even closer to that in matching two cylinders. In the classification experiment, subjects were asked to classify the shape of various virtual polyhedral approximations to a circular cylindrical bump. Without force shading, the subjects accurately identified the polyhedral nature of the virtual bumps. With force shading, however, the subjects identified the polyhedral approximations as conveying approximately the same feel as a smooth cylinder.