Planar Hand Motion Guidance Using Fingertip Skin-Stretch Feedback

In this paper, we show that a simple haptic device can accurately guide users through planar hand movements. The device guides the user through skin stretch feedback on the fingerpad of the user´s index finger. In an angle matching test evaluating two types of stimuli, users are able to discriminate between eight stimulus directions and match the motion of their hand to the stimulus direction with 10 degree accuracy. In two motion guidance tests, haptic cues effectively guide users´ arm motions through the full extent of their reachable workspace. Real-time corrective feedback greatly improves user performance, keeping average user hand motions within 12 mm of the prescribed path and within 4 degree of the indicated directions. Additionally, the paper shows that participants exhibit distorted haptic perceptual responses, finding that the distortion causes a response direction bias, but that appropriate haptic feedback can correct for the effect. Such motion guidance has applications in human-machine interaction, such as upper-extremity rehabilitation.