Dynamics and Control for a Novel One-Legged Hopping Robot in Stance Phase

Legged locomotion systems are a class of biological robots by supporting on the ground with discrete points, and can traverse nature terrain in large range. This kind of robots is a class of important research objects in robotics community in a long time. In the early time, most of the legged robot systems are static balance locomotion systems, which show a slow moving speed and high requirement in energy dissipation. During the past twenty years, many scholars were interested in dynamic legged robots for improving the performance of the systems. The one-legged hopping robots are a typical and the simplest systems of the dynamic legged robots, and can be found in many literatures, such as (Raibert,1986; Francois & Samson,1998; Gregorio et al,1997; Ahmadi & Buehler,1997,2006; Ahmadi et al, 2007; Vakasi et al, 1991; Lapshin, 1992; Papadopoulos & Cherouvim, 2004; Hyon & Emura,2002; Zeglin,1999; Guang-Ping H. & Zhi-Yong G, 2008 etc.). As it pointed out that in (Papadopoulos & Cherouvim, 2004), most of researches about the one-legged hopping robots were limited to the systems with Spring Loaded Inverted Pendulum (SLIP) model, which is composed of a point mass attached on a telescopic spring that is free to rotate around its point of contact with the ground. The SLIP model hopping systems can be stabilized without much effort in control design since the simple decoupling dynamics (Raibert et al, 1984; Raibert,1986; Francois & Samson,1998; Gregorio et al,1997; Ahmadi & Buehler, 1997, 2006; Ahmadi et al, 2007; Vakasi et al, 1991; Lapshin, 1992; Papadopoulos & Cherouvim, 2004; Hyon & Emura,2002, 2004; Zeglin,1999; Hodgins & Raibert, 1990; Hyon et al, 2004 ). It was shown that this class of hopping robots not only could stably hop but also realize some acrobatic motion such as somersaults (Raibert et al, 1984; Hodgins & Raibert, 1990). Nevertheless, the main limitations of the SLIP model systems are that the mechanical systems lose the biological characteristics and the leg of the robot commonly has translational telescopic joint. The translational telescopic legs are generally actuated by pneumatic or hydraulic actuators, and show small motion range. The pumping station of the hydraulic systems is not easy to be embedded into the robots such that the robots could not move in large range. Though (Gregorio et al,1997; Ahmadi & Buehler, 1997, 2006; Ahmadi et al, 2007) realized the hopping control on an electrically actuated experimental robot, the