1 Introduction
Although many different motion planning methods have been proposed [1] most of them are not used in practice. Complete planners are too slow to be useful except for some restricted cases, e.g. robots with two or three degrees of freedom (dot), and require a processing time that is exponential in the number of dof of the robot [4] The increasing need of practical planners for robots with many dof has focused the attention on randomized or probabilistic motion planning methods. These methods are incomplete or embed weaker notions of completeness because they will find a solution if exists given a sufficient running time.