Generating 6-D Trajectories for Omnidirectional Multirotor Aerial Vehicles in Cluttered Environments

As fully-actuated systems, omnidirectional multirotor aerial vehicles (OMAVs) have more flexible maneuverability and advantages in aggressive flight in cluttered environments than traditional underactuated MAVs. This letter aims to achieve safe flight of OMAVs in cluttered environments. We present a 3-stage pipeline to generate safe and dynamically feasible 6-D rigid body trajectories for OMAVs. Given the obstacle information and goal points, we first search a feasible initial path and represent the 3-D collision-free regions around the path by a series of intersecting convex polyhedra. Then a general 6-D trajectory optimization framework considering safety and kinodynamic constraints is presented to finally generate a feasible 6-D <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$SE(3)$</tex-math></inline-formula> trajectory, where the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$SE(3)$</tex-math></inline-formula> trajectory is represented as a 6-D polynomial in time without any inherent manifold constraints using rotation parameterization. A stereographic-based rotation parameterization is adopted to achieve more efficient optimization. To verify the proposed framework's performance, simulations and real-world experiments based on a tilt-rotor hexarotor aerial vehicle are carried out.