A deformable tri-prism rolling mechanism constructed with only R joints

In this paper, a novel deformable tri-prism rolling mechanism constructed with only revolute (R) joints is proposed. The rolling mechanism is composed of six vertices and nine planar RRR chains, forming a regular tri-prism structure with a total of seven degrees of freedom (DoFs). The kinematics of the mechanism is analyzed based on the vector loop closure method. First, two quasi-static non-impact rolling gaits, namely the pyramidal and cylindrical rolling gaits, are developed through coordinated structural deformation. Subsequently, an accelerated rolling gait with the minimum impulse is developed based on the work–energy principle and impact dynamics. A minimum-impulse criterion is formulated to determine the impact configuration, and the residual kinetic energy after impact is utilized to sustain forward rolling. Furthermore, an obstacle-crossing gait is developed to improve the terrain adaptability of the mechanism. In addition, both moving and folding performances of the tri-prism rolling mechanism are discussed. Finally, a prototype is manufactured, and the experiments have verified the feasibility of the four proposed rolling gaits as well as the moving and folding performances of the tri-prism rolling mechanism.