Hierarchical motion planning system with consideration of the dynamic lane-changing behaviour

In this paper, a hierarchical motion planning framework is proposed to solve complex navigation problem in realistic dynamic traffic environments. Firstly, according to the possible collision risk in the lane changing process, a safe lane-changing (LC) model with consideration of the emergency braking of the preceding car is established. Then a straight-line approximation method is proposed to convert the nonlinear constraints into linear constraints, which effectively improves the solution efficiency. Secondly, the quintic B-spline curve method and the quadratic programming (QP) method are integrated to screen out the optimal LC trajectory, with consideration of driving safety, traveling comfort and efficiency. Thirdly, a decision-making strategy is proposed to decide whether the trajectory should be re-planned according to the real-time prediction of the surrounding environments, and decide the optimal lane. Finally, a model predictive control (MPC) path tracker is proposed to track the planned trajectory. The CarSim-Simulink joint simulation verify the effectiveness of the proposed motion planning framework.