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Analysis of Cartesian Force Sensitivity for Joint Torque Controlled Robots

Standfest, Bastian (2016) Analysis of Cartesian Force Sensitivity for Joint Torque Controlled Robots. Master's. DLR-Interner Bericht. DLR-IB-RM-OP-2016-184, 100 S.

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Abstract

Compliant, joint torque controlled robots measure the forces and torques at the tool center point indirectly using their built-in joint torque sensors. This allows robust impedance control but has drawbacks regarding the force sensitivity, which denotes the measurable force changes in relation to the external applied force variation. Depending on the robot configuration, torque inaccuracies and joint hysteresis have varying impact on the quality of the measured forces and torques. Joint torque offsets are influencing the measurement statically, whereas friction related joint hysteresis is changing the detected torques dynamically. Therefore, a bandwidth is introduced, which specifies the measured torque deviation based on joint hysteresis. Since the hysteresis gives a statement about the possible torque variation, it can be used to define the sensitivity. A method is described, to detect these influences and transform the insights into Cartesian space. This leads to an improvement of the force measurement accuracy due to offset compensation and the force sensitivity for the manipulator can be estimated according to the hysteresis. An accurate analysis of the Cartesian force sensitivity for impedance controlled robots is inalienable when it comes to applications like automated assembly tasks, where tactile force feedback is used to compensate position inaccuracies of objects. The Cartesian force sensitivity of redundant manipulators is determined using force ellipsoids, which are capable of showing the sensitivity of the force measurement according to the spatial directions at the tool center point. Hence, a statement about the expected sensitivity in different poses and configurations is generated and verified with a proposed robotic measurement setup.

Item URL in elib:https://elib.dlr.de/105945/
Document Type:Monograph (DLR-Interner Bericht, Master's)
Title:Analysis of Cartesian Force Sensitivity for Joint Torque Controlled Robots
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Standfest, BastianUNSPECIFIEDUNSPECIFIED
Date:26 August 2016
Refereed publication:No
Open Access:No
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:No
Number of Pages:100
Status:Published
Keywords:calibration and identification, redundant robots, force and tactile sensing, kinematics, flexible arms, cooperative manipulators
Institution:Management Center Innsbruck
Department:Mechatronics - Electrical Engineering
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Space Technology
DLR - Research area:Raumfahrt
DLR - Program:R SY - Technik für Raumfahrtsysteme
DLR - Research theme (Project):R - Vorhaben Terrestrische Assistenz-Robotik
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Robotics and Mechatronics (since 2013) > Analysis and Control of Advanced Robotic Systems
Deposited By: Stemmer, Andreas
Deposited On:19 Dec 2016 12:58
Last Modified:19 Dec 2016 12:58

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