Energy-Optimal Tours for Quadrotors to Scan Moth-Infested Trees in Densely-Packed Forests

In this paper, optimal control theory is used to generate energy-optimal tree-to-tree routes by taking into account the map of the forest environment and the quadrotor's dynamics. After computing the energy consumption between all pairs of trees, a Travelling Salesman Problem is formulated and solved using Integer Linear Programming along with Sub-Tour Elimination Constraints to determine the optimal global route. The first scan is not only time-optimal but is also complete. Thus, an infection map is established after the first scan. For subsequent scans, an online solution is proposed to update the path-planner and only include a subset of the trees by considering the probability of infection of a tree based on neighboring trees.