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Whole-body Joint Friction Modeling in a Torque-controlled Humanoid Walking Robot

Egle, Tobias (2021) Whole-body Joint Friction Modeling in a Torque-controlled Humanoid Walking Robot. Student thesis, DLR.

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Previous research on friction estimation in robotic joints has been primarily focused on the dominant contribution of the drive unit friction originating in particular from the harmonic drive gear. With torque sensors mounted on the joint output side, the frictional effects of the drive units can be compensated by the torque controller to a large extend. However, in an assembled robot the friction in mechanical parts on the output side of the torque sensor still affects the actuation performance and leads to permanent control errors. This work aims at developing a whole-body friction estimation method that relies solely on internal position measurements of the robot and can capture the friction state on the output side of the joint torque sensor. Therefore, by comparison of a model-based acceleration estimate with the measured joint acceleration, obtained by numerical differentiation of the joint positions, a joint friction estimate can be determined. A simulation model is designed to evaluate the proposed method. Simulation results confirm that reliable friction torque estimates can be obtained given a sufficiently accurate dynamic model of the robot. It is shown that real-world imperfection like sensor noise, vibrations induced by the closed-loop control and inertia modeling errors limit the performance of the friction estimation in the experiment.

Item URL in elib:https://elib.dlr.de/141952/
Document Type:Thesis (Student thesis)
Title:Whole-body Joint Friction Modeling in a Torque-controlled Humanoid Walking Robot
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Date:February 2021
Refereed publication:No
Open Access:Yes
Number of Pages:48
Keywords:Whole-body, Joint Friction Modeling, Torque-control, Humanoid Robot
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Robotics
DLR - Research area:Raumfahrt
DLR - Program:R RO - Robotics
DLR - Research theme (Project):R - Walking robot/locomotion [RO]
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Robotics and Mechatronics (since 2013) > Analysis and Control of Advanced Robotic Systems
Deposited By: Englsberger, Dr.-Ing. Johannes
Deposited On:28 Apr 2021 14:55
Last Modified:28 Apr 2021 14:55

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