Human Haptic Interaction with Soft Objects: Discriminability, Force Control, and Contact Visualization

摘要

The haptic interaction of humans with soft objects was studied from three perspectives: softness discrimination, force control, and contact visualization. The abilities of humans in actively discriminating softness was measured by using a specimen presenter system which was built to randomly present the specimens. Two experimental paradigms (1-and 2-finger) and three finger condition (normal, finger cot, and rigid thimble) were used to examine the importance of various sources of information. When using 1 finger, the Just Noticeable Difference (JND) was about 5% for normal and finger cot conditions and increased to about 50% with the thimble. The JND results from 2-finger discrimination were lower than the 1-finger results for both normal and finger cot conditions, but were higher with the thimble. Examination of the forces exerted on the specimens during 2-finger discriminations revealed possible underlying discrimination strategies. In the force control experiments, subjects were asked to exert several levels of constant forces under various finger conditions. The results indicated that the errors from tracking with visual feedback was significantly lower than that without visual feedback. No significant differences in force control were found with either different softness or under the three finger conditions. The absolute errors were higher when controlling higher target forces. Significant difference is force control was found between the two bands of the subject who showed handedness in the softness discrimination experiments. For contact visualization, a real-time imaging setup was built which consisted of a video microscopy system and a tactile stimulator system. By using this setup, real-time images from the contact region as well as the contact forces were digitized. Various image processing techniques were developed and applied in order to analyze and improve the contact images to distinguish between the contact and non-contact regions.