Surveillance planning with safe emergency landing guarantee for fixed-wing aircraft.

In this paper, we study Emergency Landing Aware Surveillance Planning (ELASP) to determine a cost-efficient trajectory to visit a given set of target locations such that a safe emergency landing is possible at any point of the multi-goal trajectory. The problem is motivated to guarantee a safe mission plan in a case of loss of thrust for which it is desirable to have a safe gliding trajectory to a nearby airport. The problem combines computational challenges of the combinatorial multi-goal planning with demanding motion planning to determine safe landing trajectories for the curvature-constrained aerial vehicle. The crucial property of safe landing is a minimum safe altitude of the vehicle that can be found by trajectory planning to nearby airports using sampling-based motion planning such as RRT*. A trajectory is considered safe if the vehicle is at least at the minimum safe altitude at any point of the trajectory. Thus, a huge number of samples have to be evaluated to guarantee the safety of the trajectory, and an evaluation of all possible multi-goal trajectories is quickly computationally intractable. Therefore, we propose to utilize a roadmap of safe altitudes combined with the estimation of the trajectory lengths to evaluate only the most promising candidate trajectories. Based on the reported results, the proposed approach significantly reduces the computational burden and enables a solution of ELASP instances with tens of locations in units of minutes using standard single-core computational resources. (C) 2020 Elsevier B.V. All rights reserved.