Real-time Motion Planning of Curvature Continuous Trajectories for Urban UAV Operations in Wind

Jay Patrikar,Vishal Dugar, Vaibhav Arcot and Sebastian Scherer
Published In the proceedings of 2020 International Conference on Unmanned Aircraft Systems (ICUAS), 2020

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A key challenge in enabling autonomous Unmanned Aerial Vehicles (UAVs) to operate in cluttered urban environments is to plan collision-free, smooth, dynamically feasible trajectories between two locations with the wind in realtime. This paper presents a novel path planning strategy using sampling-based planning that uses a two-point boundary value problem (BVP) to connect states in the presence of wind. Unlike most approaches that use a curvature discontinuous solution, the proposed BVP is formulated as a nonlinear constrained optimization problem with curvature and curvature-rate continuous profile to generate smoother trajectories. To achieve real-time performance, our method uses surrogate solutions from a precalculated library while solving the planning problem and then runs a repair routine to generate the final trajectory. To validate the feasibility of the offline-online strategy, simulation results on a 3D model of an actual city block with a realistic wind-field are presented. Results with a trochoid-based BVP solver are also presented for comparison. For the given simulation scenario, we could demonstrate a 93% success rate for the algorithm in finding a valid trajectory.

Overall Approach: Offline, we generate a trajectory library of precomputed wind-agnostic BVP solutions on a predefined grid. Online, we use the trajectory library to provide wind-aware surrogate solutions to perform real-time planning. Only the surrogate solutions that are part of the final path are repaired to provide smooth collision-free wind-aware path.