“…They can be divided into two categories, the local methods and the global methods. The local methods can offer fast response in face of the obstacles with local optimization, mainly including the vector field histogram [26], motion field flow [27], the curvature-velocity method [28], and the artificial potential field approach [29,30]; the global methods can ensure that a valid and whole trajectory optimized solution can be found if it exists, but requires large computation and global representation of the environments and obstacles, mainly containing the path planning algorithms [31,32] and the global search approaches [33,34]. The artificial potential field approach, which was proposed by Khatib [29] in 1986, has been widely studied to avoid obstacles.…”