The use of virtual fixtures to enhance operator performance in time delayed teleoperation.

Abstract

Abstract : This report reviews the notion of virtual fixtures for force-reflecting telepresence systems that has been introduced in a previous report and describes an additional study which demonstrates that such fixtures can reduce performance degradation due to transmission time delay. Real world tools and fixtures can enhance performance by guiding manual operations, providing localizing references, and reducing the mental processing required to perform a task. Virtual fixtures are computer-generated precepts overlaid onto the force-reflecting master workspace that have been shown to provide similar benefits in teleoperation tasks without time delay. Virtual fixtures are superimposed on top of the presentation of the remote site, completely independent of all sensory feedback from the remote worksite (and therefore unaffected by transmission delays). As a result, virtual fixtures act as high fidelity reference points overlaid on top of an otherwise time-distorted perceptual environment. This study expands the testing of the virtual fixture concept by using simple combinations of haptic surfaces as perceptual overlays in a standardized peg-insertion task, with the goal of minimizing performance degradation due to time delay. Six subjects were tested using a force-reflecting exoskeleton master device to control a slave robot arm with no time delay, 250 ms delay, and 450 ms delay. A Fitts' law paradigm quantified operator performance for each of four fixture configurations. Without the use of virtual fixtures, operator performance was reduced by 36% for the 250 ms delay and 44% for the 450 ms delay. With the use of the most effective virtual fixtures tested, there was no measured performance degradation in the time-delayed teleoperation.