Biped Stabilization by Linear Feedback of the Variable-Height Inverted Pendulum Model

TL;DR

This paper introduces a simple linear feedback stabilizer for bipeds using the variable-height inverted pendulum model, enhancing recovery from larger disturbances by leveraging height variation of the center of mass.

Contribution

It presents a novel biped stabilization method based on linear feedback of the VHIP model, capable of handling larger perturbations than existing ankle strategies.

Findings

Effective stabilization of HRP-4 robot demonstrated

Capable of recovering from larger disturbances

Matches state-of-the-art for small perturbations

Abstract

The variable-height inverted pendulum (VHIP) model enables a new balancing strategy by height variations of the center of mass, in addition to the well-known ankle strategy. We propose a biped stabilizer based on linear feedback of the VHIP that is simple to implement, coincides with the state-of-the-art for small perturbations and is able to recover from larger perturbations thanks to this new strategy. This solution is based on "best-effort" pole placement of a 4D divergent component of motion for the VHIP under input feasibility and state viability constraints. We complement it with a suitable whole-body admittance control law and test the resulting stabilizer on the HRP-4 humanoid robot.