We will limit our analysis to the case of a robot workspace free of obstacles. In fact, we implicitly consider the robot controller to be embedded in a hierar- chical architecture in which a higher-level planner solves the obstacle avoidance problem and provides a series of motion goals to the lower control layer. In this perspective, the controller deals with the basic issue of converting ideal plans into actual motion execution. Wherever appropriate, we shall highlight the in- teractions between feedback control and motion planning primitives, such as the generation of open-loop commands and the availability of a feasible smooth path joining the current robot position to the.
