Abstract: In order to improve the practicability of the spherical robot in the unstructured task environment, the BYQ-GS spherical robot with the ability to change the centroid radially is developed, which not only has the heavy pendulum driving mode, but also has the inverted pendulum driving mode. Under the two different motion modes, it can both realize the radial centroid change function.The radial variation of centroid is considered, and the controllable influence factors during the motion process are integrated into the dynamic model construction process to realize the dynamics model for unstructured task environment in two motion modes. Based on the BYQ-GS spherical robot, the effects of inverted pendulum driving mode and radial movement of mass center on the motion of spherical robot are analyzed. The results show that compared with the heavy pendulum driving mode, the inverted pendulum driving mode has advantages in overshoot, response speed and energy consumption, and has disadvantages in convergence speed and stability.The reduction of the distance between the centroid and the ball center at the beginning of the movement can make the convergence speed, overshoot, stability and response speed of the two driving modes worse, and optimize the energy consumption.

Key words: spherical robot, mechanism design, dynamic model, motion analysis, centroid