Online Friction Coefficient Identification for Legged Robots on Slippery Terrain Using Smoothed Contact Gradients

Fuente: arXiv
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Main Authors: Kim, Hajun, Kang, Dongyun, Kim, Min-Gyu, Kim, Gijeong, Park, Hae-Won
Format: Preprint
Published: 2025
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author Kim, Hajun
Kang, Dongyun
Kim, Min-Gyu
Kim, Gijeong
Park, Hae-Won
author_facet Kim, Hajun
Kang, Dongyun
Kim, Min-Gyu
Kim, Gijeong
Park, Hae-Won
contents This paper proposes an online friction coefficient identification framework for legged robots on slippery terrain. The approach formulates the optimization problem to minimize the sum of residuals between actual and predicted states parameterized by the friction coefficient in rigid body contact dynamics. Notably, the proposed framework leverages the analytic smoothed gradient of contact impulses, obtained by smoothing the complementarity condition of Coulomb friction, to solve the issue of non-informative gradients induced from the nonsmooth contact dynamics. Moreover, we introduce the rejection method to filter out data with high normal contact velocity following contact initiations during friction coefficient identification for legged robots. To validate the proposed framework, we conduct the experiments using a quadrupedal robot platform, KAIST HOUND, on slippery and nonslippery terrain. We observe that our framework achieves fast and consistent friction coefficient identification within various initial conditions.
format Preprint
id arxiv_https___arxiv_org_abs_2502_16843
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Online Friction Coefficient Identification for Legged Robots on Slippery Terrain Using Smoothed Contact Gradients
Kim, Hajun
Kang, Dongyun
Kim, Min-Gyu
Kim, Gijeong
Park, Hae-Won
Robotics
This paper proposes an online friction coefficient identification framework for legged robots on slippery terrain. The approach formulates the optimization problem to minimize the sum of residuals between actual and predicted states parameterized by the friction coefficient in rigid body contact dynamics. Notably, the proposed framework leverages the analytic smoothed gradient of contact impulses, obtained by smoothing the complementarity condition of Coulomb friction, to solve the issue of non-informative gradients induced from the nonsmooth contact dynamics. Moreover, we introduce the rejection method to filter out data with high normal contact velocity following contact initiations during friction coefficient identification for legged robots. To validate the proposed framework, we conduct the experiments using a quadrupedal robot platform, KAIST HOUND, on slippery and nonslippery terrain. We observe that our framework achieves fast and consistent friction coefficient identification within various initial conditions.
title Online Friction Coefficient Identification for Legged Robots on Slippery Terrain Using Smoothed Contact Gradients
topic Robotics
url https://arxiv.org/abs/2502.16843