  This paper presents a free space trajectory optimization algorithm of
autonomous driving vehicle, which decouples the collision-free trajectory
planning problem into a Dual-Loop Iterative Anchoring Path Smoothing (DL-IAPS)
and a Piece-wise Jerk Speed Optimization (PJSO). The work leads to remarkable
driving performance improvements including more precise collision avoidance,
higher control feasibility and better driving comfort, as those are often hard
to realize in other existing path/speed decoupled trajectory optimization
methods. Our algorithm's efficiency, robustness and adaptiveness to complex
driving scenarios have been validated by both simulations and real on-road
tests.
