Abstract
It was clarified that speeding-up of passive dynamic walking (PDW) of a combined rimless wheel (CRW) can be achieved by adjustment of the phase difference between the fore and rear legs. We discussed the mechanism from the viewpoint of overcoming the potential barrier, and pointed out that the trajectory of the whole center of mass (CoM) is significantly flattened according to the phase difference as one of the factors. This paper investigates the possibility of speeding-up of a CRW not by having the phase difference but by adding a passive wobbling mass that vibrates up and down in the body. Our expectation is that the wobbling mass would flatten the whole CoM trajectory to realize an efficient walking. First, we numerically show that the walking speed increases by the effect of the wobbling mass and that the gait efficiency changes with respect to the viscoelasticity. Second, we analyze the transition from anti-phase to in-phase phase oscillation focusing on the frequencies of the CRW and wobbling mass. We also show nonlinear characteristics such a high sensitivity to initial conditions and hysteresis phenomenon. Furthermore, the validity of the simulation results is verified using an experimental CRW machine.
