  Safety is a fundamental requirement in any human-robot collaboration
scenario. To ensure the safety of users for such scenarios, we propose a novel
Virtual Barrier system facilitated by an augmented reality interface. Our
system provides two kinds of Virtual Barriers to ensure safety: 1) a Virtual
Person Barrier which encapsulates and follows the user to protect them from
colliding with the robot, and 2) Virtual Obstacle Barriers which users can
spawn to protect objects or regions that the robot should not enter. To enable
effective human-robot collaboration, our system includes an intuitive robot
programming interface utilizing speech commands and hand gestures, and features
the capability of automatic path re-planning when potential collisions are
detected as a result of a barrier intersecting the robot's planned path. We
compared our novel system with a standard 2D display interface through a user
study, where participants performed a task mimicking an industrial
manufacturing procedure. Results show that our system increases the user's
sense of safety and task efficiency, and makes the interaction more intuitive.
