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Volume 26 Issue 1 - Publication Date: 1 January 2007
Special Issue: The 12th International Symposium on Robotics Research
 
A Unified Passivity-based Control Framework for Position, Torque and Impedance Control of Flexible Joint Robots
 
A. Albu-Schäffer, C. Ott and G. Hirzinger Institute of Robotics and Mechatronics, German Aerospace Center (DLR), Germany
 
This paper describes a general passivity-based framework for the control of flexible joint robots. Recent results on torque, position, as well as impedance control of flexible joint robots are summarized, and the relations between the individual contributions are highlighted. It is shown that an inner torque feedback loop can be incorporated into a passivity-based analysis by interpreting torque feedbackin terms of shaping of the motor inertia. This result, which implicitly was already included in earlier work on torque and position control, can also be used for the design of impedance controllers. For impedance control, furthermore, potential energy shaping is of special interest. It is shown how, based only on the motor angles, a potential function can be designed whichsimultaneously incorporates gravity compensation and a desired Cartesian stiffness relation for the link angles. All the presented controllers were experimentally evaluated on DLR lightweight robots and their performance and robustness shown with respect to uncertain model parameters. Experimental results with position controllers as well as an impact experiment are presented briefly, and an overview ofseveral applications is given in which the controllers have been applied.
 
Multimedia Key
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Extension
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Description
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Example 1: Cartesian impedance control is used for teaching and execution of piston insertion. For comparison, the human execution is shown. (2.5 MB) m1v
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Example 2: Table wiping with simultaneous null-space movement and force control in vertical direction. (0.7 MB) m1v
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Example 3: Door opening using impedance control. (1.9 MB) m1v
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Example 4: Position control of the new humanoid system Justin. (1.4 MB) m1v
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Example 5 : Crash test experiments for safety validation. (0.8 MB) m1v
 
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