A unified framework for walking and running of bipedal robots

TL;DR

This paper introduces a flexible framework for bipedal robot locomotion that relaxes traditional assumptions, enabling diverse walking and running gaits with minimal complexity increase, and includes a disturbance-adaptive control mechanism.

Contribution

It presents a novel virtual constraints-based framework that generates varied gaits and incorporates a feedback control for disturbance adaptation, extending beyond fixed CoM height models.

Findings

Successfully generated multiple walking and running gaits in simulations.

Demonstrated robustness against environmental uncertainties and external disturbances.

Maintained low complexity while increasing gait diversity.

Abstract

In this paper, we propose a novel framework capable of generating various walking and running gaits for bipedal robots. The main goal is to relax the fixed center of mass (CoM) height assumption of the linear inverted pendulum model (LIPM) and generate a wider range of walking and running motions, without a considerable increase in complexity. To do so, we use the concept of virtual constraints in the centroidal space which enables generating motions beyond walking while keeping the complexity at a minimum. By a proper choice of these virtual constraints, we show that we can generate different types of walking and running motions. More importantly, enforcing the virtual constraints through feedback renders the dynamics linear and enables us to design a feedback control mechanism which adapts the next step location and timing in face of disturbances, through a simple quadratic program (QP). To show the effectiveness of this framework, we showcase different walking and running simulations of the biped robot Bolt in the presence of both environmental uncertainties and external disturbances.