A Practical Approach for Motion Planning of Wheeled Mobile Robots

Wheeled Mobile Robots (WMR) have been widely studied in the past fifteen years. Due to kinematic constraints, many WMR are not integrable (non-holonomic). Therefore, standard techniques developed for robot manipulators are not directly applicable. In particular, the motion planning of WMR is still a relevant issue. Examples of motion planning for WMR are available in the literature (Latombe, 1991; Laumond et al., 1997; Gracia & Tornero, 2003; Borenstein & Koren, 1989). On the other hand, the singularity of WMR kinematics must be avoided since it implies slip or impossible control actions (Gracia & Tornero, 2007a). In the same way, in the vicinity of singularities there is high amplification of active joints’ error or high values for active joints. Therefore, the aim of the present research is to develop a practical approach for motion planning of WMR based on avoiding singularities. The chapter is organized as follows. Section 2 presents the kinematics of WMR considering four types of wheels: fixed, centered orientable (hereinafter orientable), castor and Swedish. Afterwards, section 3 discusses the possibilities for motion planning and develops a cost index based on singularity. To illustrate the applications of the proposed motion planning an industrial forklift is considered and several simulation results are shown. Finally, section 4 points out the more outstanding contributions of this research.