Search-based hierarchical whole-body motion planning and control for quadrotors

Abstract

In this paper, we propose a novel search-based hierarchical whole-body motion planning framework that can divide the planning process of a quadrotor into two parts: position-only planning and attitude-aware planning. A safe flight corridor (SFC) containing spatial scale information is designed to partition collision-free regions to identify narrow regions in the environment, and the attitude-aware planning process is triggered only in narrow regions. Based on the spatial-scale SFC, a carefully designed hierarchical collision detection mechanism can constrain the attitude of the quadrotor along the trajectory to the safe corridor to ensure collision-free and accelerate the planning process. Afterward, a trajectory refinement strategy is introduced to preserve the searched safe attitude-aware trajectory segments and optimize the neighboring position-only trajectory segments with position, velocity, and acceleration continuity, ensuring smooth transitions between different planning stages. Subsequently, a differentially flat model predictive controller is used to track aggressive trajectories. Benchmark results show that the proposed method generates safe and aggressive trajectories while reducing computation time by approximately 4-9 times relative to the search-based whole-body baseline. High-fidelity simulation experiments are conducted in various unknown environments to demonstrate the feasibility of the generated trajectories.