Active Manipulation of Users in Haptic-Enabled Virtual Environments

The main goal of this research is to study the effect of subthreshold forces on human performance in a haptic-enabled virtual reality system. A multi-modal task similar to Fitts is used to study the effects of the sub-threshold forces on user performance. Each user’s movement is manipulated using controlled forces such that the user is not aware of the forces. Subjects can see the position of the haptic probe in a virtual environment where they are manipulated using sub-threshold forces. The multi-modal task is used to measure the accuracy of subjects in two experiments. During the experiments, the effects of force intensity and the relative direction of applied forces to the direction of user’s hand motion in the presence of visual cues are investigated. A performance index is also introduced that can be used to evaluate human performance in the application of subthreshold forces. A psychophysical method is utilized to ensure that the applied forces on the user’s hand are below the force threshold of the human haptic system. Results indicate that user performance is affected by both the intensity and direction of sub-threshold forces even when the users could control their actions through visual feedbacks.