Planning collision-free trajectories in time-varying environments: a two-level hierarchy

Global geometric algorithms for trajectory planning are used in conjunction with a local avoidance strategy. Simulations have been developed for a mobile robot in the plane among stationary and moving obstacles. Essentially, the robot has a geometric planner that provides a coarse trajectory (the path and the velocity along it), which may be modified by a (low-level) local avoidance module if sensors detect obstacles in the vicinity of the robot. This hierarchy makes effective use of the complementarity between global trajectory planning and local obstacle avoidance