Tactile information in a palm is a necessary component in manipulating and perceiving large or heavy objects. Noting this, we investigate human sensitivity to tactile haptic feedback in a palm for an improved user interface design. To provide distributed tactile pattern, we propose an ungrounded haptic interface, which can stimulate multiple locations in a palm, independently. Two experiments were conducted to evaluate human sensitivity to distributed tactile patterns. The first experiment tested participants' sensitivity to tactile patterns by sub-sections in a palm, and a significant effect of the sub-section on the sensitivity was observed. In the second experiment, participants identified pressure distribution patterns in the palm collected from real-life objects with the percent correct of 71.4 % and IT (information transfer) was 1.58 bits.

When one manipulates a large or bulky object, s/he utilizes tactile information at both fingers and the palm. Our goal is to efficiently convey contact information to a user's hand during interaction with a virtual object. We propose a haptic system that can provide haptic feedback to thumb/middle finger/index finger and on a palm. Our interface design utilizes a novel compact mechanism to provide haptic information to the palm. Also, we propose a haptic rendering strategy to calculate haptic feedback continuously. We demonstrate that cutaneous feedback on the palm improves the haptic perception of a large virtual object compared to when there is only kinesthetic feedback to the fingers.

We investigate the role of contact location information on the perception of local features during contour following in a virtual environment. An absolute identification experiment is conducted under force-alone and force-plus-contact-location conditions to investigate the effect of the contact location information. The results show that the participants identify the local features significantly better in terms of higher information transfer for the force-plus-contact-location condition, while no significant difference was found for measures of the efficacy of contour following between the two conditions. Further data analyses indicate that the improved identification of local features with contact location information is due to the improved identification of small surface features.

The effect of contact location information on the perception of virtual edges was investigated by comparing human edge sharpness discrimination under the force-alone and force-plus-contact-location conditions. The virtual object consisted of the 2D profile of an edge with two adjoining surfaces. Edge sharpness JNDs for both conditions increased from about 2 to 7 mm as the edge radii increased from 2.5 to 20.0 mm, and no significant difference was found between the two conditions. A follow-up experiment with the contact-location alone condition resulted in higher (worse) edge sharpness discrimination thresholds, especially at higher edge radius values. Our results suggest that contact location cues alone are capable of conveying edge sharpness information, but that force cues dominate edge sharpness perception when both types of cues are available.