A Wheel-based Stair-climbing Robot with a Hopping Mechanism

In this chapter, we introduce a stair-climbing robot developed in our laboratory. This robot consists basically of two body parts connected by springs, and hops as a result of the vibration of a two-degrees-of-freedom (2-DOF) system. The excellent combination between the frequencies of the robotic body vibration and the tread-riser interval of stairs enables a small and simple robot fast stair climbing, soft landing, and energy saving. In an attempt to give the robot mobility in an environment such as an office building having steps and stairs, various mechanisms have been proposed and developed. Each one of which has different characteristics. For example, wheel-based robots are very simple in terms of both mechanical design and control, and they can travel quickly and stably. But their size tends to be big for climbing stairs, as they cannot surmount a riser higher than their wheel radius. On the other hand, although crawler-type robots can climb over a riser higher than a wheel-based robot, they are slow and noisy. Typical examples of crawler-type robots are TAQT (Hirose et al., 1992) that can carry a human and Kenaf (Yoshida et al., 2007) for rescue operations. Legged robots, especially humanoid ones, are well suited for climbing stairs, but require many DOFs and complex control. Honda’s ASIMO (ASIMO OFFICIAL SITE), AIST’s HRP (Harada et al., 2006) and Waseda University’s legged robot (Sugahara et al., 2007) are good examples. In addition, the hybrids of these types have been proposed and have improved upon mutual demerits. Chari-be (Nakajima et al., 2004), with two wheels and four legs, travels quickly on its wheels over flat terrain, and climbs using its legs in rough terrain such as a step and stairs. A biped-type robot with a wheel at the tip of its legs (Matsumoto et al., 1999) climbs stairs smoothly. RHex (Altendorfer et al., 2001) has six compliant rotary legs and travels speedily not only up and down stairs, but also even uncertain terrain such as a swamp. Moreover, modular robots such as an articulated snakelike robot and special mechanisms for stairs have also been proposed. Yim’s snake-like robot (Yim et al., 2001) climbs stairs, transforming its own loop form into a stair shape. These excellent mechanisms have improved the manoeuvrability of the robot for rough terrain, but as most are general-purpose robots for rough terrain, a more specialized mechanism must be developed if we focus solely on stair-climbing ability in an office building. 3