Three Critical Elementary Haptic Cues Explained
Cue I : Contact Location Trajectory
During exploration of a physical shape, orientation of the exploring fingerpad is observed to remain invariant as shown in (a). The interaction between the fingerpad and stimuli thus results in deformation at the contact region of the fingerpad. This deformation may be simulated through the rolling of a flat plate that is in contact with the fingerpad according to normal exploratory movements as is represented in (b). By deforming the finger using this method, all other aspects of interaction normally present during surface exploration, such as local shape effects, sliding, proprioception etc., are eliminated resulting in the presentation of a highly simplified signal.
Cue II : Tactile Flow
During natural exploration, there also exists a relative velocity between the skin and the physical object being explored as illustrated in (a). Tactile flow is a cue for estimating this relative velocity. This cue may be presented by allowing the operator to slide along the surface of the flat plate as is represented in (c).
Cue III : Proprioception
The proprioceptive cue provides information as to changes in position of limbs and joints. When traversing over a physical shape, finger is moves in all directions as is represented in (a). This cue may be displayed by a servo controlled positioning stage that moves along the z axis, resulting the a change in height of the finger that would be observed if moving over a physical surface (see (d)).
Tactile cues presented at the fingerpad. Red bars indicate contact location while the blue arrows indicate sliding direction of the fingerpad. Tactile flow (TF) is present when sliding occurs. a) Contact location trajectory (CLT) and TF cues normally present during exploration of natural stimuli b) CLT presented by a plate rolling under the fingerpad c) CLT and TF presented by a plate rolling under the fingerpad while the fingerpad slides on the plate d) CLT, TF and proprioception (P) presented by a plate rolling under the fingerpad while the fingerpad slides on the plate and while a linear stage moves along the z axis delivering height changes normally present when traversing over natural stimuli.