Abstract: Hex-style robots can perform manifold moving gaits in different applications, but they have always faced a challenge of climbing up high obstacles. In this paper, the bionics-based gait optimization in an RHex-style robot is proposed for climbing steps at different heights, which even enables the robot to climb up the step with 4.2 times of the leg length. First, a thoracic flexion is designed in the robot, and an algorithm of adjusting body inclination is proposed to perform the rising stage after placing front legs on top of step, which can be applied in different RHex-style robots with different sizes. Especially, when the thoracic flexion is implemented, the robot can climb the higher step with the proposed algorithm. Second, to climbing the higher steps, a claw-shape legs-based algorithm is proposed for robot reaching the higher step and climbing it up. During the vital rising stage, when the front legs of the robot have reached the top of the step, the robot can bend the front body downward with its thoracic flexion like a cockroach, and then lift the front and middle legs alternately to move COM up and forward onto the step. The simulation analysis is utilized to verify the feasibility of the proposed algorithms. Finally, the step-climbing experiments at different heights are performed in our robot to compare with the existing works. The results of simulations and experiments show the superiority of the proposed algorithms for the improved robot due to climbing up the higher steps.

Key words: Mini-RHex robot, Climbing gait, Thoracic fexion, Gait optimization, Claw-shape legs