Orbital Analysis of a Passive Dynamic Biped Walker with a Torso Coupled by a Torsional Spring and Damper

Passive dynamic biped walkers are widely used to study and mimic human locomotion. However, many existing models neglect the torso, which constitutes a significant portion of the human body’s mass. This study integrates a passive torso into a passive dynamic biped walker, with a torsional spring and damper installed at the hip to maintain the torso’s upright position. Numerical simulations are conducted to evaluate the walker’s performance, and the system’s stability is rigorously analyzed using the Poincaré return map. The results reveal that a torso with well-optimized length and mass substantially enhances system stability. Furthermore, the addition of a spring and damper is critical for achieving a stable periodic gait. Notably, higher spring stiffness fosters stable walking, while slight damping significantly improves stability. These findings provide valuable insights for advancing the design of humanoid robots and walking-assist devices.