Control of Contact Forces between Robot and Free-Floating Object
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Sähkötekniikan korkeakoulu |
Master's thesis
Ask about the availability of the thesis by sending email to the Aalto University Learning Centre oppimiskeskus@aalto.fi
Authors
Date
2017-10-23
Department
Major/Subject
Space Robotics and Automation
Mcode
ELEC3047
Degree programme
Erasmus Mundus Space Master
Language
en
Pages
75
Series
Abstract
This thesis proposes an approach based on direct force control for controlling interaction between a robotic manipulator and a free-floating object. For free-floating objects, there is no fixed base to absorb reaction forces during the manipulation or assembly process. Consequently, if the interaction forces are too high, objects can gain momentum and move away after contact. Hence, the objective of the controller during manipulation is to minimize the interaction forces while maintaining contact. The proposed approach achieves this by maintaining a small constant force along the motion direction and apparent reduction of manipulator inertia along remaining degrees of freedom (DOF). Simulations were performed for the interaction forces using MATLAB platform. The results emphasize the importance of relative inertia of the robotic manipulator with respect to the free-floating object. The experiments were carried out using a two-dimensional micro-gravity emulator (object floating on air-bed) and 7-DOF KUKA LWR4+ manipulator arm. The control algorithms were implemented using OROCOS. It was verified that the proposed control law is capable of controlling the interaction forces and aligning the tools without pushing the object away. It is concluded that direct force control works better with a free-floating object than implicit force control algorithms, such as impedance control.Description
Supervisor
Kyrki, VilleThesis advisor
Suomalainen, MarkkuKeywords
robotic manipulation, space robotics, free-floating systems, interaction control