A novel HTN planning approach for handling disruption during plan execution

In this paper, we focus on how to handle disruptions during plan execution. Disruption are common in realistic plan execution, and the replanning is needed when the original plan is failed. Aiming to reduce the number of unnecessary replanning in this situation, a novel heuristic HTN (Hierarchical Task Network) planning approach is proposed. The approach includes two components: F-HTN and Controller. F-HTN is a heuristic temporal HTN planner. F-HTN uses STNs (Simple Temporal Networks) to express the complex temporal constraints in planning, and an STN-based heuristic search is designed to guide the search direction in F-HTN. When the planner F-HTN is terminated, it will generate a flexible plan which includes a complete plan and an STN associated with it. Then, Controller checks and adjusts the flexible plan when a disruption occurs during the plan execution. Integrating the plan generation and plan execution, this approach will reduce the number of unnecessary replanning. In the experimental study, we demonstrate the effectiveness and practicability of this approach through some emergency logistics problems.