Analysis of the Mecanum wheel arrangement of an omnidirectional vehicle

Mecanum wheels are widely used in omnidirectional vehicles, but their arrangements are usually arbitrarily selected. We find that the arrangement of Mecanum wheels influences the performance of an omnidirectional vehicle. The two most used arrangement modes, Type-X and Type-O, are studied. The inverse velocity Jacobian matrix of the arrangement judges whether a vehicle can fulfill omnidirectional movement. The eigenvalues of the inverse velocity Jacobian matrix and global stiffness index are proposed to evaluate the stability and dexterity of different arrangement modes. The theoretical results show that the Type-X vehicle has a larger stiffness and global stiffness index than the Type-O vehicle, which ensures that the Type-X vehicle moves more precisely and stably than the Type-O vehicle. Four types of movements (straight, sideways, diagonal, and revolving) are tested for both arrangements. The experiments show that the actual running tracks of Type-X follow the ideal running tracks well, while the performance of Type-O is much worse. Moreover, an external force is subjected to both arrangements. The results illustrate that the behavior of the Type-X vehicle is more stable than that of Type-O.