Toward Varying Bipedal Walking Gaits Using Rolling Ball-Tray Dynamics at the Walker’s Core

Actuated compass-gait walking machines have the potential to navigate areas with gentle slopes using very little energy, but a technological solution for applying a torque that will drive its natural gait is still proving elusive. In this paper, we investigate a mechatronic solution that could provide a driving force to a compass-gait walker: a heavy ball rolling in a V-shaped tray that is composed of circular arcs and straight segments. By tilting the tray, the ball can be made to roll back and forth. The equations of motion derived for this system are numerically simulated and compare favorably with the ball’s response in experiments. We then interpret the ball’s motion as a center-of-mass shift at the hips of a simulated walker to investigate what effects a ball-tray system would have on the compass-gait. When the ball’s motion under suitable tray geometry and tilt profile was applied as a mass shift at the hip to a compass-gait walking simulation, several feasible gait solutions were found. This suggests that the tilting ball-tray actuation method may be a suitable drive strategy for operating physical bipeds. In the long term, these results may be used to develop a system that can excite the walking dynamics of the biped from the core to create variable styles of walking gaits as described in Laban-Bartenieff movement theory.