Controlling lateral stepping of a biped robot by swinging torso toward energy efficient walking

In this paper, we propose a controller for stable lateral stepping of a humanoid which utilizes the passive phase and changes the swinging phase of torso by the ground contact of the swing leg. Although the passive phase makes use of the gravitational power, the existence of the passive phase makes it difficult to control the period of the motion. We utilize the relationship between the amplitude of swinging torso and the motion period so that the desired period of lateral stepping is realized. Combined with a simple controller for walking in the sagittal plane, our proposed controller can enable 3-D walking with short step length.