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Introduction

Stair climbing is one of the most attractive performance of mobile robot for both legged and wheeled. (e.g. Stoeter et al., 2002; Murphy, 2000; Yim et al., 2000; Krishna et al., 1997;Granosik et al., 2005; Liu et al., 2005; Arai et al., 2006; Tanaka et al., 2006; Miyanaka et al.,2007; Tsukagoshi et al.,2005)Authors have been developing various kinds of stair climbers, considering how to make itsclimbing ability higher and its mechanical complexity easonable and practical. The researchincludes realizing a large step negotiating height, controlling to keep its centre of gravity almost the centre of ground contacting area, higher speed of climbing up, large load tolerance to carry on. Reducing body weight and energy consumption is also the important matter of developing In the first part of this chapter, we introduce some solutions to realize stair climbing machines that we developed. Each of them has good performance as in a category of their kind, e.g. various numbers of legged and wheeled shapes. Then, we discuss a development of high-grip crawler, which we think one of the best solutions as the stair climber.

The Stair Problem

A robot which moves freely in a building has to be adapted to an environment made for humans. On its way it may encounter small obstacles ( up to 4 cm of hight, e.g. door steps, sills  etc.) and stairs. These stairs often have nosings or ledges and sometimes open risers. The slope of indoor stairs can vary between  25° and 42°. Sometimes you will find in residental buildings even steeper stairs, especially spiral stairs. In public buildings stairs often have a rise s of 17cm and a run a of 29cm (slope approx. 30°)

Well-known Stair Climbing Robots

If you search the internet, you will find quite a number of stair climbing robots. There are the famous

-two-legged robots( e.g. Asimo, HRP2 ),

-six-legged robots ( e.g. RHex ), and

-tracked robots, mainly in military or law enforcement applications (e.g. Urbie, packBot).

Looking for wheeled robots you will find only a small selection. Best known probably shrimp of the EPFL Lausanne.  Helios V also climbs up and down stairs. There are also some hybrid designs with rotating legs, a mixture of a wheel and a 1-DOF-leg:  whegs, whegsII and mini-whegs IV ( and RHex). Mini-whegs IV  uses yet another concept: It jumps from step to step.

In the amateur area are successful stair climbers too, for example the Lego robot P’titgneugneu. It climbs stairs in both directions, but it is not well suited for floors, due to its design especially developed for stair climbing.