Mechanism and Control of Anthropomorphic Biped Robots

Human beings, animals and some birds use their legs to move with great mobility, but we do not yet have a full understanding of their motion mechanism. The reason is that we lack man-made robots that use legs to obtain high mobility. We, especially, need two-legged robots that are able to adapt to human living environments such as offices and homes. In order to analyze a human walking mechanism, some research groups studied about hydraulically-actuated or pneumatically-activated two-legged mechanisms in the 1960s. In 1973, a world’s first full-scale anthropomorphic robot, WABOT-1 (WAseda roBOT-1), was constructed at Waseda University as shown in Figure 1. It was able to communicate with a human in Japanese and to measure the distance and direction of objects using external receptors such as an artificial mouth, ears and eyes (Kato et al., 1973). Hydraulically powered, it used disproportionately large feet for stability. Also, it was able to grip and carry objects using the hands that were equipped with tactile sensors. In 1983, WL-10R (Wasada Leg-10 Refined) was constructed using rotary type servoactuators and carbon-fiber reinforced plastic. It was able to walk forwards and backwards, and turn on a flat plane. Based on the WL-10R, WHL-11 was developed by Wasada and Hitachi (Takanishi et al., 1985). It walked more than 85 km at Tsukuba Science Expo’85. In 1986-1995, WL-12 series robots that have a trunk and a 2-DOF waist was constructed to simulate human walking motion including his upper body motion as shown in Figure 2 (Takanishi et al., 1988; Li et al., 1992; Yamaguchi et al., 1995). They performed dynamic walking going up and down a stair with a height of 0.1 m and a slope of 10 deg (Takanishi et al., 1990). Also, they did not fall down and walked under an unknown external force of 100 N applied to their backs (Takanishi et al., 1991). However, the relative motion between their upper body and legs was difficult to be simulated. An electrically powered human-sized biped humanoid robot, WABIAN (WAseda BIped humANoid), was constructed in 1996 for simulating human motion. It consists of a total of 35 DOF; two 3-DOF legs, two 10-DOF arms, two 2-DOF eyes, a 2-DOF neck and a torso with a 3-DOF waist (Setiawan et al., 1999). After 1996, WABIAN series robots were developed, and achieved qusi-human follow walking, emotional motion, dancing motion and so on (Setiawan et al., 1999; Lim et al., 2004a).