Kinematic modeling and singularity of wheeled mobile robots

Abstract

This paper presents a global singularity analysis for wheeled mobile robots (WMRs). First, a kinematic model of a generic wheel is obtained using a recursive kinematics formulation. This novel and efficient approach is valid for all the common types of wheels: fixed, centered orientable, off-centered orientable (caster or castor) and Swedish or Mecanum. Then, a procedure for generating robot kinematic models is presented based on the set of wheel equations and the null space concept. Next, the singularity of kinematic models is discussed: first, the kinematic singularity condition in forward models is obtained, and then the singularity condition in inverse, or even mixed, models. A generic and practical geometric approach is established to characterize the singularity of any kinematic model of any WMR with the mentioned wheels. To illustrate the applications of the proposed approach, the singular configurations for many types of WMRs are depicted. Finally, the singularity characterization is extended to include other specialized wheels: dual-wheel, dual-wheel castor, ball-type and orthogonal.