Among the several designs of mobile robots, the wheel design is unfavorable for navigation of stairs or over obstacles. The leg design and the creeping design demand very intricate control systems and are not efficient on flat surfaces. The caterpillar design is unreliable and unstable in stair navigation. In the arm-wheel design, the sensor which discriminates between stairs and flat surfaces and the mechanism which alternates between wheel-running and arm-creeping modes are complicated. In this paper, a new type of arm-wheel design for a mobile robot enabling it to navigate stairs is developed, which requires no sensor for discrimination between stairs and flat surfaces of stairs and no mechanism for alternating between wheel-running and arm-creeping modes. Since no sensor is required, the reliability in an extreme environment is high. Moreover, since it has no intricate discrimination mechanism, it can also be applied to a wheelchair, for example, which is not powered. The author has confirmed through experiments using a stair-navigating robot prototype that the mechanism developed here functions as intended.
