BiDSpoke: A Leg-Wheel Robot With Bidirectionally Transformable and Isotropic Spoke Wheels

To address the challenge that existing transformable spoke wheel robots struggle to achieve balanced climbing performance in both forward and backward directions, a bidirectionally transformable and isotropic spoke wheel robot has been designed. The robot features a four-spoke wheel design, with each spoke wheel driven by two independent motors. The transformation of the spoke wheels is achieved through a combination of gear and linkage transmission. The symmetrical design of the transmission system ensures that the spoke wheels exhibit equivalent climbing capabilities and structural strength in both forward and backward directions, which is a property defined as isotropy. This design enables the robot to switch between hook-shaped and arc-shaped forms without altering its orientation, enhancing operational efficiency and reducing the risk of entrapment in scenarios where turning is restricted. This article presents a design methodology for the spoke wheel and evaluates the torque requirements for driving, along with the stair climbing capabilities. A prototype of the robot was developed, and various experiments were conducted on different terrains, including flat ground, steps, and stairs. The results demonstrate that the proposed design method for the transformable spoke wheel is practical, and robots utilizing this mechanism show great potential for real-world inspection tasks.