Gait analysis and efficiency improvement of passive dynamic walking of combined rimless wheel with wobbling mass

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 potential barrier, and showed that the trajectory of the whole center of mass (CoM) is significantly flattened by choosing the phase difference. This paper investigates the potentiality of speeding-up the CRW without having the phase difference but by using a passive wobbling mass that vibrates up and down in the body in expectation of flattening the whole CoM trajectory. We show that the walking speed is increased by the effect of the wobbling mass and that a transition from anti-phase to in-phase oscillation arises with the increase of the elasticity. 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.