Vibrotactile Phantom Sensations in Haptic Wrist Rotation Guidance

Haptic motion guidance has the potential to advance assistive technologies that support humans in movement tasks. This study systematically evaluates wrist rotation guidance methods in a 2 × 2 repeated measures design using a wearable vibrotactile feedback device. In two tasks, we investigate the benefits of encoding the current target distance in the cue strength and conveying additional information about the target location by incorporating a tactile illusion known as phantom sensation. For a directional response task, we analyze reaction times and error rates, and for an angle targeting task, we examine rise time, settling time, and maximum overshoot of the normalized step responses. These objective criteria are complemented by subjective user ratings that assess the intuitiveness and ease of interpreting the vibrotactile cues. Feedback methods incorporating an adaptive amplitude perform significantly better in the angle targeting task compared to those using a constant amplitude. Additional improvements can be achieved by combining the adaptive amplitude with phantom sensations, including an average additional 24.3% reduction in rise time. Furthermore, more than half of the participants rate this combination as their favorite method. Altogether, the results underline the potential of incorporating phantom sensations in vibrotactile wrist guidance, thereby contributing to the advancement of wearable haptics in assistive applications.