A Mechanism for Smoothly Handling Human Interrupts in Team Oriented Plans

Team oriented plans have become a popular tool for operators to control teams of autonomous agents (or robots) to pursue complex objectives in complex environments. Such plans allow an operator to specify high level directives and allow the team to autonomously determine how to implement such directives. However, the operators will often want to interrupt the activities of individual team members to deal with particular situations, such as a danger to a robot that the robot team cannot perceive. Previously, after such interrupt, the operator would usually need to restart the team plan to ensure its success. In this paper, we present an approach to encoding how unexpected interrupts can be smoothly handled within a team plan. Building on a team plan formalism that uses Colored Petri Net, we describe a mechanism that allows a range of interrupts to be handled smoothly, allowing the team to efficiently continue with its task, after the operator intervention. We validate the approach with an application of robotic watercraft and show improved overall efficiency. In particular, our interrupt mechanism decreases the time to complete the mission (up to 48% reduction) and decreases the operator load (up to 80% reduction in number of user actions).