Robust Footstep Planning and LQR Control for Dynamic Quadrupedal Locomotion

TL;DR

This paper presents a robust quadrupedal locomotion framework combining fast model predictive foothold planning with LQR-based control, effectively handling disturbances and uncertainties in real-time.

Contribution

It introduces a novel integration of high-frequency foothold planning with LQR control and inverse dynamics for enhanced robustness in quadrupedal robots.

Findings

Demonstrated robustness to external disturbances.

Achieved stable locomotion on uncertain terrains.

Validated on the ANYmal robot with successful experiments.

Abstract

In this paper, we aim to improve the robustness of dynamic quadrupedal locomotion through two aspects: 1) fast model predictive foothold planning, and 2) applying LQR to projected inverse dynamic control for robust motion tracking. In our proposed planning and control framework, foothold plans are updated at 400 Hz considering the current robot state and an LQR controller generates optimal feedback gains for motion tracking. The LQR optimal gain matrix with non-zero off-diagonal elements leverages the coupling of dynamics to compensate for system underactuation. Meanwhile, the projected inverse dynamic control complements the LQR to satisfy inequality constraints. In addition to these contributions, we show robustness of our control framework to unmodeled adaptive feet. Experiments on the quadruped ANYmal demonstrate the effectiveness of the proposed method for robust dynamic locomotion given external disturbances and environmental uncertainties.