Hierarchical Optimization for Whole-Body Control of Wheeled Inverted Pendulum Humanoids

TL;DR

This paper introduces a hierarchical whole-body control framework for Wheeled Inverted Pendulum Humanoids, enabling simultaneous task execution while respecting joint constraints and optimizing control across multiple degrees of freedom.

Contribution

It proposes a novel hierarchical control approach with separate high-level and low-level controllers for efficient and coordinated whole-body management of WIP humanoids.

Findings

Effective control of WIP humanoids demonstrated

Hierarchical approach improves task prioritization

Computational efficiency achieved through model approximation

Abstract

In this paper, we present a whole-body control framework for Wheeled Inverted Pendulum (WIP) Humanoids. WIP Humanoids are redundant manipulators dynamically balancing themselves on wheels. Characterized by several degrees of freedom, they have the ability to perform several tasks simultaneously, such as balancing, maintaining a body pose, controlling the gaze, lifting a load or maintaining end-effector configuration in operation space. The problem of whole-body control is to enable simultaneous performance of these tasks with optimal participation of all degrees of freedom at specified priorities for each objective. The control also has to obey constraint of angle and torque limits on each joint. The proposed approach is hierarchical with a low level controller for body joints manipulation and a high-level controller that defines center of mass (CoM) targets for the low-level controller to control zero dynamics of the system driving the wheels. The low-level controller plans for shorter horizons while considering more complete dynamics of the system, while the high-level controller plans for longer horizon based on an approximate model of the robot for computational efficiency.