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On the Passivity Based Impedance Control of Flexible Joint Robots

Ott, Christian and Albu-Schäffer, Alin and Kugi, Andreas and Hirzinger, Gerd (2007) On the Passivity Based Impedance Control of Flexible Joint Robots. IEEE Transactions on Robotics.

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Abstract

In this work a novel type of impedance controllers for flexible joint robots is proposed. As a target impedance a desired stiffness and damping are considered without inertia shaping. For this problem two controllers of different complexity are proposed. Both have a cascaded structure with an inner torque feedback loop and an outer impedance controller. For the torque feedback, a physical interpretation as a scaling of the motor inertia is given, which allows to incorporate the torque feedback into a passivity based analysis. The outer impedance control law is then designed differently for the two controllers. In the first approach the stiffness and damping terms and the gravity compensation term are designed separately. This outer control loop uses only the motor position and velocity, but no noncollocated feedback of the joint torques or link side positions. In combination with the physical interpretation of torque feedback, this allows us to give a proof of the asymptotic stability of the closed-loop system based on the passivity properties of the system. The second control law is a refinement of this approach, in which the gravity compensation and the stiffness implementation are designed in a combined way. Thereby, a desired static stiffness relationship is obtained exactly. Additionally, some extensions of the controller to visco-elastic joints and to Cartesian impedance control are given. Finally, some experiments with the DLR lightweight robots verify the developed controllers and show the efficiency of the proposed control approach.

Document Type:Article
Title:On the Passivity Based Impedance Control of Flexible Joint Robots
Authors:
AuthorsInstitution or Email of Authors
Ott, ChristianUNSPECIFIED
Albu-Schäffer, AlinUNSPECIFIED
Kugi, AndreasUNSPECIFIED
Hirzinger, GerdUNSPECIFIED
Date:2007
Journal or Publication Title:IEEE Transactions on Robotics
Status:Published
Keywords:Impedance Control, Compliance Control, Flexible Joint Robots, Passivity Based Control.
HGF - Research field:Aeronautics, Space and Transport (old)
HGF - Program:Space (old)
HGF - Program Themes:W SY - Technik für Raumfahrtsysteme
DLR - Research area:Space
DLR - Program:W SY - Technik für Raumfahrtsysteme
DLR - Research theme (Project):W - Weiterentwicklung Robotik - Telerobotik und Autonomie (old)
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Robotics and Mechatronics > Robotic Systems
Deposited By: Monika Klauer
Deposited On:04 Nov 2008
Last Modified:12 Dec 2013 20:33

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