Abstract
The passive walker with knees can naturally execute the leg motion, which is essential to take a step forward, by the dynamics of legs under the gravity only. On the other hand, an inadequate dynamics causes an undesirable leg motion, such that the stance leg bends at the knee joint, the swing leg unsuitably strikes its foot on the slope and the walker falls backward by the negative gravitational moment. Though an arc foot is very important for the leg motion, its dynamical effects and mechanism have never been clarified, and a useful design framework of its shape has never been established. In this study, for the sake of simplicity and clarity, the linearized simplest walking model is used. In this paper, the dynamical effects of the arc foot, which can keep the knee joint of stance leg straight only by the stopper and can enhance the flexion of knee joint of swing leg, are discussed. Also, its geometrical negative effect is examined. Furthermore, the forward-falling condition of the walker is derived based on the energy analysis. Finally, the desired arc foot is designed and the actual effects are confirmed by a walking experiment.
