Abstract: An internal locomotion mechanism of a spherical omnidirectional rolling robot is designed. Four linear motors move inward and outward respectively along four spokes with geometrical symmetry in three dimensional space, which will cause the robot to roll in all directions on a flat surface by displacing its gravity center. Based on the nonholonomic constraint arising from rolling contact and the discrete motion nature of stepper linear motors, the motion model of the robot is established. The second-order control differential equations are derived. Then an algorithm for trajectory planning is developed. A numerical example is given to illustrate the methods for motion analysis and trajectory planning. The virtual prototype technology is used to validate the effectiveness of the methods.

Key words: spherical robot, omnidirectional rolling, motion analysis, trajectory planning, virtual prototype