Abstract: Spherical mobile robot is characterized by compact structure and agile motion, thus possessing unique advantages in the application fields such as environment exploration. This article introduces the structure and motion principle of BHQ-2, a newly designed spherical mobile robot equipped with two cameras, and discusses its kinematic motion control. Since this robot belongs to a kind of nonholonomic system, and has no inverse position resolution, its motion control problem at the velocity level is studied. Based on screw theory the Jacobian matrix of BHQ-2 is deduced and its inverse velocity resolution is obtained by means of generalized inversion. With control Lie algebra, the BHQ-2 robot system is proved to be full rank, therefore it is completely nonholonomic and controllable. Simulations and experiments of straight line trajectory and circular trajectory motions of BHQ-2 are done based on the inverse velocity resolution, and the results of simulations and experiments validate the controllability of the robot and the correctness of the inverse velocity resolution of the robot.

Key words: spherical robot, screw, Jacobian matrix, inverse velocity resolution, nonholonomic system