Orbit Characterization, Stabilization and Composition on 3D Underactuated Bipedal Walking via Hybrid Passive Linear Inverted Pendulum Model
This work addresses gait control for 3D underactuated walking robots, offering a methodology for continuous gait generation and stabilization, though it appears incremental as it builds on existing models like the Linear Inverted Pendulum.
The authors tackled the problem of generating and stabilizing periodic walking orbits for 3D underactuated bipedal robots by proposing a Hybrid passive Linear Inverted Pendulum model, resulting in smooth gait generation and stabilization from stepping-in-place motion for models like aSLIP and the Cassie robot.
A Hybrid passive Linear Inverted Pendulum (HLIP) model is proposed for characterizing, stabilizing and composing periodic orbits for 3D underactuated bipedal walking. Specifically, Period-1 (P1) and Period-2 (P2) orbits are geometrically characterized in the state space of the H-LIP. Stepping controllers are designed for global stabilization of the orbits. Valid ranges of the gains and their optimality are derived. The optimal stepping controller is used to create and stabilize the walking of bipedal robots. An actuated Spring-loaded Inverted Pendulum (aSLIP) model and the underactuated robot Cassie are used for illustration. Both the aSLIP walking with P1 or P2 orbits and the Cassie walking with all 3D compositions of the P1 and P2 orbits can be smoothly generated and stabilized from a stepping-in-place motion. This approach provides a perspective and a methodology towards continuous gait generation and stabilization for 3D underactuated walking robots.