Contraction Control of Swing Leg for Smooth Wheel Gait Generation of Planar X-shaped Walker with Telescopic Legs

The authors have been studying methods generating a stable wheel gait of a biped robot in which the swing leg is rotated in the same direction as the stance leg. In our previous study, we succeeded in generating an asymptotically stable wheel gait for a planar X-shaped walker with telescopic legs by achieving constraint on impact posture. In this paper, for the same robot model, we propose a control method to mitigate the impact at fore-foot landing by contracting the swing-leg length immediately before impact in order to generate smoother and more energy efficient wheel gait, and analyze the effect of this on gait efficiency through numerical simulations. In particular, we discuss the importance of the target terminal length and contraction speed of the swing leg, using the impulses acting on the rear and fore feet at impact as an indicator.