Whole-Body Impedance Coordinative Control of Wheel-Legged Robot on Uncertain Terrain

TL;DR

This paper introduces a whole-body impedance control framework for wheel-legged robots that enhances adaptability and stability on complex terrains through a bi-level control strategy and real-time terrain estimation.

Contribution

It presents a novel bi-level control framework combining impedance control and whole-body optimization with terrain estimation for improved robot stability and adaptability.

Findings

Successfully maintains upper body stability during water-carrying tasks.

Adapts to varying terrains effectively in real-time.

Demonstrates improved control performance on a quadruped humanoid robot.

Abstract

This article propose a whole-body impedance coordinative control framework for a wheel-legged humanoid robot to achieve adaptability on complex terrains while maintaining robot upper body stability. The framework contains a bi-level control strategy. The outer level is a variable damping impedance controller, which optimizes the damping parameters to ensure the stability of the upper body while holding an object. The inner level employs Whole-Body Control (WBC) optimization that integrates real-time terrain estimation based on wheel-foot position and force data. It generates motor torques while accounting for dynamic constraints, joint limits,friction cones, real-time terrain updates, and a model-free friction compensation strategy. The proposed whole-body coordinative control method has been tested on a recently developed quadruped humanoid robot. The results demonstrate that the proposed algorithm effectively controls the robot, maintaining upper body stability to successfully complete a water-carrying task while adapting to varying terrains.