Reconstructing human push recovery reactions using a three dimensional under-actuated bipedal robot

This paper presents the ability of hybrid zero dynamics (HZD) feedback control method to reproduce human like movements for walking push recovery of an under-actuated 3D biped model. The balance recovery controller is implemented on a three-dimensional under-actuated bipedal model subjected to a push disturbance. The biped robot model is considered as a hybrid system with eight degrees of freedom (DOF) in the single support phase and two degrees of under-actuation in the ankle joint. The control is done based on the method of virtual constraints and HZD, by adjusting the desired trajectory of the event-based feedback controller. Several simulations have been done considering pushes exerted during walking. The results showed the performance of the method in recovery of pushes occurring in the sagittal and frontal planes and also in the both directions, simultaneously. The results showed that the simulated motions can be characterized in terms of strategies observed in human for balance recovery against perturbations during walking.