Quantifying Feedback Modality Contributions for a Haptic Glove in VR Assembly

Abstract

An integral part of creating compelling and useful immersive virtual environments is the presence of haptic feedback, where both kinesthetic and cutaneous feedback convey unique information critical to object handling and manipulation. State-of-the-art haptic gloves are broadening the workspace and degrees of freedom for hand motion in VR, adding force and vibrotactile feedback to the user's hand and fingers. The effect of each feedback modality to task performance remains unclear. In the current proof-of-concept study we added high-frequency vibrotactile actuators onto a resistive force-feedback glove, to illustrate how our proposed analysis method might contribute to the field of human factors studies. We aim to identify improvements to a haptic glove by isolating the contribution of both haptic feedback modalities, that is the force and vibrotactile feedback. Haptic gloves are used to train the fine motor control skills for assembly operations, allowing the users to grasp objects in an natural manner. By tracking the Finger Indentation -- the distance that a fingertip travels into the virtual surface of the grasped object -- we can capture the grasping realism achieved by each haptic condition. This approach allows us to explore the differences between expected physical world behavior and corresponding behavior in a virtual environment. To determine if our proposed metric provides insights into human behavior, we perform a within-subject comparison of a simplified assembly task in virtual reality with 3 participants. Participants are asked to perform a pick-and-place task for 4 conditions: no feedback, vibrotactile feedback, force feedback, and combined feedback. Performance is judged by analysing task completion time, finger indentation, and subjective measurements. The results of this proof-of-concept study suggest that the combined feedback condition performs better in terms of lower thumb indentations and higher usefulness and satisfactory scores than the no feedback and vibrotactile feedback conditions. It is notable that the vibrotactile feedback condition did not seem to out-perform the no-feedback condition. Regardless, the finger indentation metric seems to be a valid method to compare feedback modalities for grasping performance in a full-sized human factors study.