Investigating the Perception of Translational Shape-Changing Haptic Interfaces

Shape-changing haptic interfaces (SCHIs) are a promising and emerging field. However, compared to more established stimulus modalities, such as vibration, there is sparse literature on the perception of dynamic shapes. Furthermore, the influence of properties such as grasp types and displacement magnitude/direction has not been formally evaluated. This work attempts to initiate a formal perceptual evaluation of SCHIs via a psychophysical user study involving a 1-DOF translational shape-changing interface that can move its body with 1.25-micrometer resolution. Participants completed a Method of Constant Stimulus study while holding the device with three different grasps. Stimuli direction occurred both toward and away from the thumb, while the standard stimuli varied between small (0.48 mm) and large (6 mm). Our results indicate that translational SCHIs should maximize the translation magnitude rather than the number of fingers in contact. We also demonstrated how to apply our findings to real-world applications via a simple 'paddle game', where we compared conventional linear mapping with non-linear mapping derived from our perceptual experiment outcomes between the device position and its represented value. Results indicate that the non-linear mapping was more effective, with improved error distribution. We hope this work inspires further formal perceptual investigation into other SCHI morphologies.