Robot motion planning: the case of nonholonomic mobiles in a dynamic world

The authors present a trajectory planner whose purpose is to determine a smooth trajectory C which is maneuver free and collision free with respect to the static obstacles of the world. C is made up of straight segments and of circular arcs connected so that C is of class C¹ and the circular transitions are determined by building and searching a particular domain called the `space of curvature centers´. They describe a motion controller which is concerned with the online execution of a motion plan made up of the trajectory C and of time constraints of the type `reach location l at time t´. The motion controller operates on a discretized model of the local environment of the vehicle. This model is used to adapt the behaviour of the vehicle to the characteristics of its actual environment (to avoid the other vehicles in particular). This is achieved using a potential fields approach allowing the vehicle to follow as closely as possible the given nominal trajectory and to satisfy as much as possible the associated time constraints