Safety Metrics for Obstacle Avoidance Trajectories of an Autonomous Helicopter

This paper discusses safety metrics associated with obstacle avoidance trajectories of an autonomous helicopter. First of all, the applicability of different norm-based metrics from the literature for assessing safety of UAV trajectories is carried out. It is shown that the current metrics cannot robustly capture all the information contained in an obstacle avoidance trajectory, and hence, a new metric is developed to account for both the vehicle distance to obstacles and its trajectory smoothness from a safety perspective. The new metric is evaluated using a comprehensive simulation model of the GTMax UAV test bed. Based on the simulation results, an approach for choosing the value of the clearance distance parameter in vehicle guidance algorithms for a selected value of safety metric is developed.