HiLo: Learning Whole-Body Human-like Locomotion with Motion Tracking Controller

TL;DR

This paper introduces HiLo, a reinforcement learning framework that enables humanoid robots to achieve natural, agile, and resilient human-like locomotion by combining motion tracking controllers with domain randomization and residual learning.

Contribution

The paper presents a novel RL-based framework that decomposes whole-body control into open-loop and residual parts, improving naturalness and adaptability of humanoid robot locomotion.

Findings

The motion tracking controller achieves natural, agile locomotion.

The framework demonstrates robustness to external disturbances.

Humanoid motion patterns can be quickly adapted without fine-tuning.

Abstract

Deep Reinforcement Learning (RL) has emerged as a promising method to develop humanoid robot locomotion controllers. Despite the robust and stable locomotion demonstrated by previous RL controllers, their behavior often lacks the natural and agile motion patterns necessary for human-centric scenarios. In this work, we propose HiLo (human-like locomotion with motion tracking), an effective framework designed to learn RL policies that perform human-like locomotion. The primary challenges of human-like locomotion are complex reward engineering and domain randomization. HiLo overcomes these issues by developing an RL-based motion tracking controller and simple domain randomization through random force injection and action delay. Within the framework of HiLo, the whole-body control problem can be decomposed into two components: One part is solved using an open-loop control method, while the residual part is addressed with RL policies. A distributional value function is also implemented to stabilize the training process by improving the estimation of cumulative rewards under perturbed dynamics. Our experiments demonstrate that the motion tracking controller trained using HiLo can perform natural and agile human-like locomotion while exhibiting resilience to external disturbances in real-world systems. Furthermore, we show that the motion patterns of humanoid robots can be adapted through the residual mechanism without fine-tuning, allowing quick adjustments to task requirements.