Trunk viscoelasticity and gait stability in quadruped walking

This study is a feasibility study on the viscoelastic properties of the spinal structure and the stability of the gait in a quadruped locomotion robot with a spinal structure. The leg motions in locomotion are periodic, so the gait is parametrized by the phase difference between each leg motion. On the other hand, we modeled the spinal structure as a sequentially connected structure of vertebrae and intervertebral discs. The structure has nonlinear viscoelastic properties. This study analyzed the viscoelastic properties of the spinal structure and the stability of multiple gait conditions using a simple two-inertia system model. We compared the analysis results using the two-inertia system model with the gait conditions observed by hardware experiments. We confirmed that various stable gait conditions depend on the trunk stiffness and locomotion speed.