A Theoretical Explanation for the Relative Leg Stiffness of Animals

One approach in the field of legged locomotion is to use theoretical models and analysis to provide basic knowledge [1]. One particular group of these models with rotary hip torque and radial leg damping has demonstrated a greater degree of robust stability and biological relevance. The previously developed Clock Torqued Spring-Loaded Inverted Pendulum [3] and Torque-Actuated Dissipative Spring Loaded Inverted Pendulum [4] both have a controlled hip torque as well as leg damping and are fully asymptotically stable. Recently, a simplified model of locomotion with hip forcing and leg damping called the Hip-actuated SLIP [5] has been developed and analyzed to study the effects of forcing and damping on the stability of locomotion. An important next step would be to use these hip actuated models to explain the near universality of relative stiffness in animal locomotion.