*4.4. On the Closed-Loop Tractability of the Proposed Planner*

This subsection reports the closed-loop tracking performance in CarSim when following the open-loop paths planned by the proposed planner (Figure 11). A linear quadratic regulator (LQR) is adopted as the controller. As illustrated in Figure 12, the open-loop and closed-loop paths do not differ much, which indicates that the planned paths are sufficiently smooth and thus easy to track. The concrete closed-loop tracking simulation results are presented in the following video link: https://www.bilibili.com/video/av677126688 (accessed on 8 December 2021).

**Figure 11.** CarSim simulation scenario layout and screenshot of simulation process.

**Figure 12.** Path planning results, w.r.t. tractability: (**a**) Case 1; (**b**) Case 2.
