  In this paper, we propose a robust and efficient quadrotor motion planning
system for fast flight in 3-D complex environments. We adopt a kinodynamic path
searching method to find a safe, kinodynamic feasible and minimum-time initial
trajectory in the discretized control space. We improve the smoothness and
clearance of the trajectory by a B-spline optimization, which incorporates
gradient information from a Euclidean distance field (EDF) and dynamic
constraints efficiently utilizing the convex hull property of B-spline.
Finally, by representing the final trajectory as a non-uniform B-spline, an
iterative time adjustment method is adopted to guarantee dynamically feasible
and non-conservative trajectories. We validate our proposed method in various
complex simulational environments. The competence of the method is also
validated in challenging real-world tasks. We release our code as an
open-source package.
