Learning Quadrupedal Locomotion for a Heavy Hydraulic Robot Using an Actuator Model

Fuente: arXiv
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Main Authors: Lee, Minho, Kim, Hyeonseok, Kim, Jin Tak, Park, Sangshin, Lee, Jeong Hyun, Cho, Jungsan, Hwangbo, Jemin
Format: Preprint
Published: 2026
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author Lee, Minho
Kim, Hyeonseok
Kim, Jin Tak
Park, Sangshin
Lee, Jeong Hyun
Cho, Jungsan
Hwangbo, Jemin
author_facet Lee, Minho
Kim, Hyeonseok
Kim, Jin Tak
Park, Sangshin
Lee, Jeong Hyun
Cho, Jungsan
Hwangbo, Jemin
contents The simulation-to-reality (sim-to-real) transfer of large-scale hydraulic robots presents a significant challenge in robotics because of the inherent slow control response and complex fluid dynamics. The complex dynamics result from the multiple interconnected cylinder structure and the difference in fluid rates of the cylinders. These characteristics complicate detailed simulation for all joints, making it unsuitable for reinforcement learning (RL) applications. In this work, we propose an analytical actuator model driven by hydraulic dynamics to represent the complicated actuators. The model predicts joint torques for all 12 actuators in under 1 microsecond, allowing rapid processing in RL environments. We compare our model with neural network-based actuator models and demonstrate the advantages of our model in data-limited scenarios. The locomotion policy trained in RL with our model is deployed on a hydraulic quadruped robot, which is over 300 kg. This work is the first demonstration of a successful transfer of stable and robust command-tracking locomotion with RL on a heavy hydraulic quadruped robot, demonstrating advanced sim-to-real transferability.
format Preprint
id arxiv_https___arxiv_org_abs_2601_11143
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Learning Quadrupedal Locomotion for a Heavy Hydraulic Robot Using an Actuator Model
Lee, Minho
Kim, Hyeonseok
Kim, Jin Tak
Park, Sangshin
Lee, Jeong Hyun
Cho, Jungsan
Hwangbo, Jemin
Robotics
Artificial Intelligence
The simulation-to-reality (sim-to-real) transfer of large-scale hydraulic robots presents a significant challenge in robotics because of the inherent slow control response and complex fluid dynamics. The complex dynamics result from the multiple interconnected cylinder structure and the difference in fluid rates of the cylinders. These characteristics complicate detailed simulation for all joints, making it unsuitable for reinforcement learning (RL) applications. In this work, we propose an analytical actuator model driven by hydraulic dynamics to represent the complicated actuators. The model predicts joint torques for all 12 actuators in under 1 microsecond, allowing rapid processing in RL environments. We compare our model with neural network-based actuator models and demonstrate the advantages of our model in data-limited scenarios. The locomotion policy trained in RL with our model is deployed on a hydraulic quadruped robot, which is over 300 kg. This work is the first demonstration of a successful transfer of stable and robust command-tracking locomotion with RL on a heavy hydraulic quadruped robot, demonstrating advanced sim-to-real transferability.
title Learning Quadrupedal Locomotion for a Heavy Hydraulic Robot Using an Actuator Model
topic Robotics
Artificial Intelligence
url https://arxiv.org/abs/2601.11143