On the energetics of quadrupedal bounding with and without torso compliance

This paper examines the influence of torso compliance on the efficiency of quadrupedal running with a bounding gait. Two sagittal-plane models, one with and one without torso compliance, are developed in a template setting. The models feature non-trivial leg mass, and are coupled with a simple leg recirculation controller to generate bounding motions. Despite their simplicity, the proposed models are sufficiently expressive to capture the energetics of bounding motions and to assess the contribution of torso flexibility to gait efficiency measured by the cost of transport. Comparisons reveal that torso compliance promotes locomotion performance by reducing energy consumption only at speeds that are sufficiently high.