Variable-Leg-Spring Hopping with Velocity-Dependent Stiffness

Even though biological legs operate amazingly springlike, they clearly deviate from a perfect spring. For instance, experimental data of human hopping and running suggest an increase in leg length and a decrease in leg stiffness between touchdown and takeoff. Here, this variability of human gait is considered as a fundamental system property and introduced via non-constant leg parameters to a 1-DOF spring-mass model. This approach may help overcome the need for precise parameter tuning and complex control schemes in artificial legged locomotory systems.