Robust Bipedal Walking With Closed-Loop MPC: Adios Stabilizers

Abstract

We propose a novel walking control scheme based on the dynamics of the Linear Inverted Pendulum (LIP) model. The pattern generation incorporates a model of contact forces, enabling closed-loop control of the humanoid robot's state, including the Center of Mass (CoM) position, velocity, and Zero Moment Point (ZMP). No additional control policies are required to maintain static and dynamic balance. Our approach also includes dynamic re-planning of step locations and timings, thus preserving the LIP's boundedness condition. We validated this controller on five different humanoid robots, testing its robustness through various disturbances, including sudden pushes during walking and static phases. Additionally, our controller demonstrated effective locomotion over uneven and compliant terrain. Both simulation and experimental results confirm the effectiveness and robustness of this controller.