A Reactive and Efficient Walking Pattern Generator for Robust Bipedal Locomotion

TL;DR

This paper presents a reactive walking pattern generator for bipedal robots that combines CoP modulation, step adjustment, and angular momentum regulation using an optimal control approach to enhance robustness against disturbances.

Contribution

It introduces a novel, integrated method employing a small QP and LIPM with flywheel dynamics for generating robust, dynamically consistent walking patterns.

Findings

The approach effectively improves walking stability under disturbances.

Simulation results demonstrate robustness and dynamic consistency.

The method adapts step location and timing based on DCM measurements.

Abstract

Available possibilities to prevent a biped robot from falling down in the presence of severe disturbances are mainly Center of Pressure (CoP) modulation, step location and timing adjustment, and angular momentum regulation. In this paper, we aim at designing a walking pattern generator which employs an optimal combination of these tools to generate robust gaits. In this approach, first, the next step location and timing are decided consistent with the commanded walking velocity and based on the Divergent Component of Motion (DCM) measurement. This stage which is done by a very small-size Quadratic Program (QP) uses the Linear Inverted Pendulum Model (LIPM) dynamics to adapt the switching contact location and time. Then, consistent with the first stage, the LIPM with flywheel dynamics is used to regenerate the DCM and angular momentum trajectories at each control cycle. This is done by modulating the CoP and Centroidal Momentum Pivot (CMP) to realize a desired DCM at the end of current step. Simulation results show the merit of this reactive approach in generating robust and dynamically consistent walking patterns.