Perception of Skin Stretch Applied to Palm: Effects of Speed and Displacement

Skin stretch is a powerful haptic effect with a great potential as a feedback mechanism for digital gaming applications. For example, it has been shown to communicate directional information accurately to game players. However, the existing devices apply stretch to the tip of index finger except the Reactive Grip game controller by Tactical Haptics, which applies skin stretch to a user's palm and finger pads. We have designed a compact hand-held haptic device that applies skin stretch to the palm via an actuated tactor. Compared to the fingertip, the palm is slightly less sensitive to skin stretch but affords larger stretch area. The stretch area of the palm enables us to control both tactor displacement and speeds for a broader range, resulting in richer haptic feedback. Using this device, we conduct experiments with 8 participants to investigate the effects of tactor displacement, speed, direction and hand orientation on perceived magnitude of skin stretch. The results of the study show that not only the tactor displacement but also the speed has a significant effect on the perceived intensity of skin stretch and the mapping function between them is nonlinear. Moreover, it appears that the tactile sensitivity of human palm to skin stretch is not homogeneous and stretch applied to the radial aspect of palm towards the thumb results in higher intensity than that of ulnar aspect.