Abstract: A new kind of rolling mechanism is proposed. This mechanism is able to deform between triangular bipyramid and spheroid with two corresponding mobile modes. When it is a triangular bipyramid, rolling function can be realized by transformation and the eccentric block controls direction switching. It can be folded into a spheroid which driven by a eccentric block. Folding mechanism is used to realize the motion function and decrease the storage space by single degree of freedom. It is proved that there are three freedoms by analysing the structure. Rolling gait is confirmed by kinematics analysis. The results of the simulated model show that the rolling mechanism can transform between the two modes and pass the prospective path. A prototype is manufactured to test the feasibility of deforming method and rolling function, and the theory is proved by its performance.

Key words: folding mechanism;triangular bipyramid：rolling mechanism