A Field Robot with Rotated-claw Wheels

With the development of space science and technology, some countries have launched unmanned planetary exploration programs. Because planet surfaces are rough and formidable, planetary exploration rovers were used as a versatile and safe alternative to manned space missions to explore the planets. In recent years, many types of planetary rovers were developed including tracked type, legged type, and wheeled type, etc. (Li et al., 2005). Because wheeled rovers are well suited to provide smooth motion and offer a high payload capacity, they become the most popular and the mainstream in current rovers (Salemo et al., 2002). In order to deal with the rough terrains of planetary surfaces, researchers put most of the efforts in designing new structure of rover body, but give less attention to new types of wheel. Currently, three main classes of wheels are used in planetary rovers as follows: (1) Traditional Circular Wheel. Representations are the wheels of Mars exploration rover Spirit (Lindemann et al., 2006) developed by JPL and Japanese rover Micro5 (Takashi et al., 2003). This type of wheel has a circular shape with a lot of transverse striae spaced evenly around the wheel to increase the friction between ground and the wheel. The wheels are commonly used in most of the rovers that can move smoothly and turn around agilely. But its fatal disadvantage is that it can not scale the step whose height is larger than the radius of the wheel, also it can not cross the ditch whose width is larger than the diameter of the wheel. (2) Flexible flake wheel. The representation is the wheel of Mars rover made by Toshiba in Japan (Liu et al., 2002). This kind of wheel is circular too, but the difference is that there are lots of flexible flake spaced evenly around the wheel. Compared with the first type wheel, this wheel increases buffering, and it can traverse over the step whose height is larger than the radius of the wheel. However, it can not cross the ditch whose width is larger than the diameter of the wheel. (3) Multiple planetary wheel. A representative example is the wheel of Lunar rover developed by Harbin Institute of Technology (HIT) in China. The lunar rover uses planetary wheel which consists of three small circular wheels (Deng et al., 2003; Deng et al., 2004). When the lunar rover moves on flat terrain, only two small wheels touch ground. Once it encounters a big obstacle or step, the three small wheels revolve around the public center of