Envelop-Climbing Locomotion Planning and Capability Analysis of a Deformable Tetrahedron Rolling Robot

This paper proposes an envelop-climbing locomotion planning for vertical obstacles by concave polyhedron construction in order to achieve high terrain adaptability of polyhedron robots. Using the triangle outline of the supporting area, a Z-shape path planning along the section of terrains is proposed. Three actions (Bridging, Enveloping and Climbing) for obstacle-crossing are sequentially planned and analyzed by constructing the external shape of concave polyhedrons to cover obstacles in the path. The kinematics analysis of the obstacle-crossing critical state for each action is established. The expression of central mass (CM), obstacle height and distance are deduced by homogeneous transformation matrix. The numerical solution of the maximum height along with motion angle and distance is figured out. Meanwhile, obstacles with different heights can be passed by executing a combination of the three different actions of the obstacle-crossing locomotion. The results of our analysis show that the locomotion can realize an obstacle-crossing ability with 170% of the height of CM. A prototype is manufactured to verify the envelop-climbing locomotion for obstacle-crossing (see video).