Humanoid Control Under Interchangeable Fixed and Sliding Unilateral Contacts

TL;DR

This paper introduces a real-time whole-body control strategy for humanoid robots that allows seamless switching between fixed and sliding contacts, ensuring balance and precise contact force control in multi-contact scenarios.

Contribution

The authors develop a quadratic programming-based control method that enables real-time switching between contact modes without precomputing balance regions, improving adaptability in humanoid robot balance management.

Findings

Successful experimental demonstrations of contact mode switching

Effective control of contact forces and CoM trajectories

Maintained balance during contact interchanges

Abstract

In this letter, we propose a whole-body control strategy for humanoid robots in multi-contact settings that enables switching between fixed and sliding contacts under active balance. We compute, in real-time, a safe center-of-mass position and wrench distribution of the contact points based on the Chebyshev center. Our solution is formulated as a quadratic programming problem without a priori computation of balance regions. We assess our approach with experiments highlighting switches between fixed and sliding contact modes in multi-contact configurations. A humanoid robot demonstrates such contact interchanges from fully-fixed to multi-sliding and also shuffling of the foot. The scenarios illustrate the performance of our control scheme in achieving the desired forces, CoM position attractor, and planned trajectories while actively maintaining balance.