Hopping Dynamics of the Internal-Torque-Actuated Asteroid Surface Rover

The hopping rover, especially the internal-torque-actuated (hopping) rover, is currently recognized as one of the most suitable type for asteroid surface exploration. Although such rovers have been successfully demonstrated in the Hayabusa 2 mission, their dynamical and control problem of its hopping motion has not been studied enough. Consequently, this paper first builds the rover's hopping dynamical model based on the Polygonal Contact Model in considering the flywheel braking process. The hopping motion is then numerically simulated on two kinds of planes, including an ideally flat plane and a complex rocky terrain. Furthermore, the parametric studies of the rover's hopping process are implemented by considering the flywheel's non-constant reaction torque during braking, the multi-contact, the surface deformation, and the slip cases. Particularly, the multiple times of micro-contact phenomenon between the rover and the asteroid surface before the departure is discovered. The effect of the flywheel's braking process, contact stiffness, and friction coefficient on the hopping characteristics of the rover are investigated. Moreover, their intrinsic dynamical mechanisms are also illustrated. This study could provide a reference for future missions that require roving on the surface of a small celestial body.