Pseudo force presentation to multiple fingers by asymmetric rotational vibration using a motor: Consideration in grasping posture

It is known that a pseudo force sensation of pulling in one direction is generated by presenting an asymmetrical vibration stimulus with different accelerations in a round trip. The present study employed a similar phenomenon using the asymmetric rotational vibration of a direct-current motor to present the pseudo force sensation to multiple fingertips. We investigated the frequency characteristics of this phenomenon for two fingers (i.e., the thumb and index finger) in a grasping posture, showing that vibration at a frequency around 30 Hz is optimal. We experimentally found that the equivalent physical force that this illusion generates is 10 to 30 grams, with large variance among participants in the study.