Abstract: Inspired by the cockroach’s use of a pitch-roll mode traverses through narrow obstacles, we improve the RHex-style robot by adding two sprawl joints to adjust the body posture, and propose a novel pitch-roll approach that enables an RHex-style robot to traverse through two cylindrical obstacles with a spacing of 90 mm, about 54% body width. First, the robot can pitch up against the obstacle on the one side by the cooperation of its rear and middle legs. Then, the robot rotates one side rear leg to kick the ground fast, meanwhile the sprawl joint on the other side rotates inward to make the robot roll and fall forward. Finally, the robot can rotate the legs on the ground to move the body forward until it crosses the obstacles. In this article, both cylinder and rectangular columns are considered as the narrow obstacles for traversing. The experiments are demonstrated by using the proposed approach, and the results show that the robot can smoothly traverse through different narrow spaces.

Key words: RHex-style robot , · Sprawl joint , · Pitch-roll mode , · Narrow obstacles