The artificial potential field based path planning has been most wisely used for local path planning because it provides simple and efficient motion planners for practical purposes. However, this approach has a local minimum problem which can trap a robot before reaching its goal. The local minimum problem is sometimes inevitable when a mobile robot moves in unknown environments, because the robot cannot predict local minima before it detects obstacles forming the local minima. The avoidance of local minima has been an active research topic in the potential field based path planning. In this study, we propose a new concept using a virtual hill to escape local minima that occur in local path planning for a mobile robot. A virtual hill is located around local minimum to repel a robot from local minimum. Copyright © 2005 IFAC Keywords: mobile robot, path planning, artificial potential field, virtual hill, extra potential, navigation.
ITRODUCTIONArtificial potential field methods provide simple and effective motion planners for practical purposes (Lee and Park, 1991). These approaches have been widely applied to path planning of a mobile robot and a manipulator (Borenstein and Koren, 1989;Chuang, 1998;Chuang and Ahuja, 1998;Chuang et al., 2000;Guldner and Utkin, 1995;Haddad et al., 1998;Hwang and Ahuja, 1992;Tsai et al, 2001;Vadakkepat, 2001;Veelaert and Bogaerts, 1999). The applications of artificial potential field for obstacle avoidance was first developed by Khatib (Khatib, 1985;Khatib, 1986). This approach uses two types of potential, which are a repulsive potential field to force a robot away from obstacles or forbidden regions and an attractive potential field to drive the robot to its goal. The robot moves under the action of the artificial force which is proportional to the negative gradient of artificial potential. The robot is driven from the positions with the higher potential to that with the lower potential.However, the path planning by the artificial potential field approach has a major problem, a local minimum problem, which can trap a robot before reaching its goal. The local minimum problem is sometimes unavoidable in local path planning, because the robot can detect only local information on obstacles. In other words, the robot cannot predict local minima before experiencing the environment. An avoidance of a local minimum has been an active research topic in potential field based path planning (Chang, 1996;Cho and Kwon, 1996;Connolly et al., 1990; Connolly, 1992;Janabi-Sharifi and Vinke, 1993;Kim and Khosla, 1992; Lee and Park, 1991;McFetridge and Yousef-Ibrahim, 1998;Park and Lee, 2003; Rimom and Koditschek, 1992;Volpe and Khosla, 1990). However, the previous solutions were limited to simple formations of obstacles or available for path planning in known environments.