The potential field method is used for creating a virtual force, acting on the robot, to attract the robot to a desired target point and to push the robot away from nearby obstacles at the same time. Two relative distances between obstacles and current robot position as well as between current robot locations and the target point help to compute the repulsive force and the attractive force, respectively. The advantage of the potential field are 1) the virtual force can be updated in real time such that the robot path in the global occupancy grid does not need to be pre-planned in advance and 2) the planning method can be coupled directly to the potential field. Its main disadvantage is that the robot might be trapped at the local minim position. The potential field is comprised of two potential functions as the following