Whole-Body Control With Terrain Estimation of A 6-DoF Wheeled Bipedal Robot

TL;DR

This paper presents a comprehensive control framework for a 6-DoF wheeled bipedal robot that integrates terrain estimation and full-body dynamics to improve traversal over uneven terrain, validated through simulations and real-world tests.

Contribution

It introduces a complete dynamics model and a hierarchical control framework with terrain estimation, addressing limitations of previous simplified models and enhancing terrain adaptability.

Findings

Effective terrain estimation using LiDAR and PCA

Robustness demonstrated in uneven terrain traversal

Hierarchical control improves stability and motion control

Abstract

Wheeled bipedal robots have garnered increasing attention in exploration and inspection. However, most research simplifies calculations by ignoring leg dynamics, thereby restricting the robot's full motion potential. Additionally, robots face challenges when traversing uneven terrain. To address the aforementioned issue, we develop a complete dynamics model and design a whole-body control framework with terrain estimation for a novel 6 degrees of freedom wheeled bipedal robot. This model incorporates the closed-loop dynamics of the robot and a ground contact model based on the estimated ground normal vector. We use a LiDAR inertial odometry framework and improved Principal Component Analysis for terrain estimation. Task controllers, including PD control law and LQR, are employed for pose control and centroidal dynamics-based balance control, respectively. Furthermore, a hierarchical optimization approach is used to solve the whole-body control problem. We validate the performance of the terrain estimation algorithm and demonstrate the algorithm's robustness and ability to traverse uneven terrain through both simulation and real-world experiments.