Angular Divergent Component of Motion: A step towards planning Spatial DCM Objectives for Legged Robots

TL;DR

This paper extends the Divergent Component of Motion (DCM) concept to include angular coordinates, enabling spatial planning for legged robots with both linear and rotational objectives, validated through simulations and hardware tests.

Contribution

It introduces the angular DCM theory, integrating rotational objectives into the existing linear DCM framework for the first time.

Findings

Angular DCM theory for 1D rotation developed

Combined 3D linear and 1D angular DCM framework proposed

Validated with MATLAB simulations and hardware on TORO humanoid

Abstract

In this work, the Divergent Component of Motion (DCM) method is expanded to include angular coordinates for the first time. This work introduces the idea of spatial DCM, which adds an angular objective to the existing linear DCM theory. To incorporate the angular component into the framework, a discussion is provided on extending beyond the linear motion of the Linear Inverted Pendulum model (LIPM) towards the Single Rigid Body model (SRBM) for DCM. This work presents the angular DCM theory for a 1D rotation, simplifying the SRBM rotational dynamics to a flywheel to satisfy necessary linearity constraints. The 1D angular DCM is mathematically identical to the linear DCM and defined as an angle which is ahead of the current body rotation based on the angular velocity. This theory is combined into a 3D linear and 1D angular DCM framework, with discussion on the feasibility of simultaneously achieving both sets of objectives. A simulation in MATLAB and hardware results on the TORO humanoid are presented to validate the framework's performance.