Contact Force Perception with an Ungrounded Haptic Interface

Two haptic interfaces, each able to provide either grounded or ungrounded haptic feedback, were constructed. Tests were conducted to compare a subject’s ability to perform boundary detection and object size discrimination tasks with grounded or ungrounded haptic feedback, with or without vision. Not surprisingly, grounded feedback is better than ungrounded feedback in displaying forces that stem from grounded sources. However, ungrounded haptic feedback can give comparable results in boundary detection tests. Subjects also reported that the application of forces to the fingertips by a moving paddle, as employed in the ungrounded tests and in some of the grounded tests, enhanced the realism of the virtual boundary contacts. Additional results concerning the synchronization of different feedback mechanisms and the use of a brake for grounded feedback are discussed in terms of their implications for the design of haptic interfaces.