Balance control using both ZMP and COM height variations: A convex boundedness approach

TL;DR

This paper introduces a convex, real-time control method for 3D biped robot balance that leverages ZMP and COM height variations, using a boundedness condition to ensure capturability of CoM trajectories.

Contribution

It proposes a low-dimensional, convex approach for 3D CoM control that is computationally efficient and handles both ZMP and COM height variations.

Findings

Enables real-time 3D balance control in biped robots.

Uses boundedness condition to ensure capturability of trajectories.

Achieves stable 3D walking with a convex optimization framework.

Abstract

Developments for 3D control of the center of mass (CoM) of biped robots are currently located in two local minima: on the one hand, methods that allow CoM height variations but only work in the 2D sagittal plane; on the other hand, nonconvex direct transcriptions of centroidal dynamics that are delicate to handle. This paper presents an alternative that controls the CoM in 3D via an indirect transcription that is both low-dimensional and solvable fast enough for real-time control. The key to this development is the notion of boundedness condition, which quantifies the capturability of 3D CoM trajectories.