Design and Control of Compliant Legged Systems

Inspired by nature, where elastic elements in muscles and tendons largely
contribute to the impressive locomotion capabilities, the quadruped robot
StarlETH is built mechanically compliant. In each of the twelve joints, serial
springs provide the necessary robustness to perform dynamic maneuvers.
They improve energetic efficiency by intermittently storing energy, and they
enable precise torque control for elaborate interaction with the environment.
We specifically engineer the mechanical properties of the actuators to support
the natural dynamics of running gaits and provide low-level control
techniques to precisely regulate the joint torque and position.
The performance of the applied design, actuation, and low-level control
approach is evaluated in planar single leg hopping experiments. To this end,
the motion is generated and stabilized by emulating bio-inspired locomotion
templates. Thereby, the leg can passively recover as much as 64% of the
energy, while the peak power and speed at the joint are more than four times
higher than at the corresponding motor. These findings are highly consistent
with different biomechanical studies and the underlying control principles can
be directly extended to multi-legged systems.