Target Position and Safety Margin Effects on Path Planning in Obstacle Avoidance

Abstract

This study examined how people choose their path to a target, and the visual information they use for path planning. Participants avoided making contact with an obstacle as they walked to a bookcase and picked up a cup from different locations on a shelf. Participants chose a path with a smaller deviation angle from a straight line to the target and chose a side of the obstacle which was closer to them. Unlike previous studies which have not included a safety margin in their analyses, we found that the right and left safety margins combined to account for 26% of the variability in path planning decision making. In some cases, participants chose a longer path around the obstacle even when the available safety margin which would have resulted in a straight line to the target was large enough to allow passage. Gaze analysis findings showed that participants directed their gaze to minimize the uncertainty involved in successful task performance and that gaze sequence changed with obstacle location. Early in their walk to the target, the greatest allocation of gaze was on the safety margin and target, later in their walk, gaze shifted to the safety margin when it was small, and then gaze shifted primarily to the target after the participant passed the obstacle. Our results of a path selection judgment test showed that the threshold for participants abandoning their preferred side for circumventing the obstacle was 15 cm to the left of the bookcase shelf center.

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